Dr. Matt Walker: How to Structure Your Sleep, Use Naps & Time Caffeine

00:00:00.000 | - Welcome to the Huberman Lab Guest Series,

00:00:02.440 | where I and an expert guest discuss science

00:00:05.120 | and science-based tools for everyday life.

00:00:07.320 | I'm Andrew Huberman, and I'm a professor of neurobiology

00:00:11.520 | and ophthalmology at Stanford School of Medicine.

00:00:14.800 | Today marks the third episode

00:00:16.400 | in our six-episode series all about sleep

00:00:19.000 | with expert guest, Dr. Matthew Walker.

00:00:21.320 | During today's episode, we discuss

00:00:22.920 | how to structure your sleep for optimal mental health,

00:00:25.680 | physical health, and performance.

00:00:27.400 | We discuss monophasic sleep schedules,

00:00:29.520 | which are the more typical sleep schedule

00:00:31.240 | where you go to sleep at night

00:00:32.480 | and then wake up in the morning,

00:00:33.640 | so sleeping in one bout,

00:00:35.160 | as opposed to polyphasic sleep schedules,

00:00:37.720 | which are when you sleep in two or more bouts,

00:00:40.880 | either at night or perhaps a shorter bout of sleep at night

00:00:43.720 | and another bout of sleep during the day.

00:00:45.800 | We also discuss naps, including how to nap,

00:00:49.120 | how long your nap should be,

00:00:50.400 | whether or not naps are good or bad,

00:00:52.600 | in particular, whether or not they're good or bad for you.

00:00:54.720 | It turns out this varies according to individual.

00:00:57.080 | We also discuss how your needs for sleep and naps

00:00:59.800 | vary across the lifespan.

00:01:01.720 | And we discuss body position during sleep,

00:01:04.080 | which might seem excessively detailed,

00:01:06.080 | but it turns out that body position during sleep

00:01:08.240 | is critical for ensuring that the sleep you get

00:01:11.160 | is optimally restorative.

00:01:13.120 | As with the first two episodes of this six-episode series,

00:01:16.480 | today's third episode is filled with both science,

00:01:20.000 | that is the biology of sleep and napping and body position

00:01:23.440 | and how those relate to one another,

00:01:25.280 | as well as practical tools that you can use

00:01:27.600 | to vastly improve your sleep.

00:01:29.440 | Before we begin, I'd like to emphasize that this podcast

00:01:32.080 | is separate from my teaching and research roles at Stanford.

00:01:34.760 | It is, however, part of my desire and effort

00:01:36.880 | to bring zero cost to consumer information about science

00:01:39.520 | and science-related tools to the general public.

00:01:42.200 | In keeping with that theme,

00:01:43.440 | I'd like to thank the sponsors of today's podcast.

00:01:46.080 | Our first sponsor is BetterHelp.

00:01:47.920 | BetterHelp offers professional therapy

00:01:49.600 | with a licensed therapist carried out online.

00:01:52.200 | I've been doing therapy for well over 30 years.

00:01:54.800 | Initially, I had to do therapy against my will,

00:01:56.880 | but of course, I continued to do it voluntarily over time

00:02:00.000 | because I really believe that doing regular therapy

00:02:02.480 | with a quality therapist is one of the best things

00:02:04.920 | that we can do for our mental health.

00:02:06.600 | Indeed, for many people, it's as beneficial

00:02:08.520 | as getting regular physical exercise.

00:02:10.280 | The great thing about BetterHelp

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00:02:21.000 | somebody with whom you can talk about

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00:02:28.000 | And with BetterHelp, they make it extremely convenient

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00:02:39.680 | Again, that's betterhelp.com/huberman.

00:02:42.880 | Today's episode is also brought to us by Element.

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00:02:49.040 | That means plenty of the electrolytes,

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00:02:53.520 | As I mentioned before on this podcast,

00:02:55.520 | I'm a big fan of salt.

00:02:56.880 | Now, I wanna be clear,

00:02:57.720 | people who already consume a lot of salt,

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00:03:07.440 | However, if you're somebody who eats pretty clean,

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00:04:02.040 | Today's episode is also brought to us by Waking Up.

00:04:04.900 | Waking Up is a meditation app

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00:05:39.180 | And now for my conversation with Dr. Matthew Walker.

00:05:42.480 | Dr. Walker, welcome back.

00:05:44.120 | - Dr. Huberman, an absolute pleasure.

00:05:46.760 | - Let's talk about the different types of sleep

00:05:48.920 | because I think most people think of sleep

00:05:51.240 | as just one thing.

00:05:52.440 | Most people sleep at night.

00:05:53.600 | Some people also nap, a topic we'll also discuss today.

00:05:57.040 | But it turns out there are a lot of different types of sleep.

00:06:01.920 | What are the different types of sleep

00:06:03.360 | and what do they do for us?

00:06:05.000 | And I guess everyone's probably wondering already.

00:06:08.260 | I certainly am.

00:06:09.840 | What types of sleep are we already engaging in?

00:06:12.480 | Meaning am I involved in

00:06:15.120 | or having multiple types of sleep each night?

00:06:16.960 | - This is a fascinating question

00:06:18.680 | and it comes back to something we've discussed

00:06:20.440 | in a previous episode.

00:06:22.160 | The different stages of sleep and how they unfold,

00:06:25.300 | we've described that fascinating stuff.

00:06:27.800 | What you're already asking though

00:06:29.320 | is an incredibly sort of subtle but relevant question.

00:06:34.260 | How should I be sleeping in terms of the phases of sleep?

00:06:38.840 | Should I have one phase?

00:06:40.640 | Should I have two phases of sleep

00:06:42.680 | or should I have many phases of sleep?

00:06:45.920 | In some ways you can answer that question

00:06:47.760 | on the basis of the lifespan

00:06:50.360 | because how it is that we sleep

00:06:52.820 | in terms of those chunking sessions changes as we develop.

00:06:57.820 | To be clear in nomenclature,

00:07:01.800 | I'm saying monophasic, biphasic, polyphasic, unpack that.

00:07:07.380 | Monophasic obviously just simply means a single phase,

00:07:10.820 | monophasic.

00:07:12.100 | - And when you say phase, you mean one bout of sleep?

00:07:14.380 | - Correct.

00:07:15.200 | So that would be within a 24 hour period,

00:07:17.480 | you are having a single bout of sleep.

00:07:20.460 | Biphasic then means that within that 24 hour phase,

00:07:24.120 | you are having two bouts of sleep.

00:07:26.700 | And we'll speak about how those bouts are split up.

00:07:30.980 | Are they split up between two halves

00:07:33.400 | in the middle of the night

00:07:34.540 | or are they split up in terms of longer at night

00:07:38.060 | and siesta like nap in the afternoon?

00:07:40.540 | And then we can speak about polyphasic sleep.

00:07:43.180 | Polyphasic sleep, we in sleep science

00:07:45.820 | have been using for many years in the context of infancy

00:07:49.940 | because there as any new parents will know,

00:07:53.300 | infants do not just simply have a nice single bout of sleep.

00:07:57.620 | They're up, they're down, they're up, they're down.

00:07:59.300 | And they have many bouts of sleep

00:08:01.300 | within that 24 hour period and that's polyphasic sleep.

00:08:05.100 | The other term or the other application of that term,

00:08:09.620 | polyphasic sleep has been used more so

00:08:11.940 | in the sort of interesting biohacker movement.

00:08:14.760 | And we'll come back to that perhaps later on.

00:08:17.740 | So how do these different phases of sleep

00:08:21.020 | change across the lifespan?

00:08:22.140 | Well, we've already said that when you're an infant

00:08:24.940 | and you're first born, within the first year of life,

00:08:28.000 | you are incredibly polyphasic

00:08:30.420 | and you are probably going through wake sleep phases

00:08:34.780 | every two hours.

00:08:36.500 | Why do you do that?

00:08:37.940 | Why can't you just simply be born

00:08:40.420 | and sleep in a monophasic way?

00:08:42.180 | It's for at least two reasons.

00:08:43.700 | First, an infant needs to feed every two hours.

00:08:47.580 | So their energy needs and their food intake requirements

00:08:51.940 | dictate that you can't sleep for very long

00:08:55.020 | because you need to be awake to feed

00:08:56.580 | and then you go back to sleep.

00:08:58.740 | Within probably the first six months,

00:09:01.780 | things will start to change a little bit.

00:09:04.500 | But the second reason that you are highly polyphasic

00:09:07.580 | when you are first born

00:09:09.020 | is because your suprachiasmatic nucleus,

00:09:12.140 | and in another episode,

00:09:13.620 | we spoke about the central master 24-hour clock

00:09:17.020 | that beats out your circadian rhythm,

00:09:19.020 | the rise and the fall, the wake and the sleep.

00:09:22.400 | That has not yet developed.

00:09:23.980 | It hasn't been glued into place into the brain,

00:09:26.700 | this 24-hour clock.

00:09:28.380 | So the infant seemingly knows nothing about when it's light

00:09:33.380 | or when it's dark outside.

00:09:35.700 | They're just awake or asleep, awake or sleep.

00:09:38.380 | So that's the second reason.

00:09:39.940 | Energy feeding needs is the first,

00:09:42.340 | and then an absence of yet a fully developed

00:09:45.340 | 24-hour clock in the brain

00:09:47.380 | to beat out that beautiful dictated rhythm.

00:09:50.900 | By about age one,

00:09:53.260 | that number of phases of sleep are starting to decrease,

00:09:57.060 | but it's still highly polyphasic.

00:09:59.060 | It's not until you get to probably age two or three

00:10:03.180 | that now you're starting to see this consolidation of sleep.

00:10:06.900 | What do I mean by that?

00:10:08.340 | Sleep is now happening more dominantly

00:10:11.340 | in the night phase of the 24-hour cycle.

00:10:14.860 | And there are fewer bouts of sleep during the daytime.

00:10:18.660 | Then perhaps by the time you're in kindergarten,

00:10:21.620 | you may be down to just two sleeps.

00:10:24.340 | So now we've switched from polyphasic sleep as infants

00:10:29.340 | to biphasic sleep as kindergarten.

00:10:32.420 | - Could you describe those biphasic patterns?

00:10:34.340 | I recall in kindergarten having nap time in the afternoon.

00:10:38.380 | - Yeah.

00:10:39.220 | - They'd put out these little mats

00:10:40.420 | and every kid would just kind of like roll up.

00:10:42.860 | It's actually sounds really nice.

00:10:44.140 | - It's one, you know, wouldn't,

00:10:45.700 | and we'll speak about how some adults do this too,

00:10:48.900 | but almost every kindergarten system

00:10:51.540 | that I've inquired about around the world,

00:10:54.300 | different nations, they all have this nap time.

00:10:58.700 | And any teacher will tell you

00:11:00.980 | if one of those children does not nap

00:11:04.220 | during that period of time, they are the loose cannon.

00:11:07.980 | They are the live wire.

00:11:09.860 | And in subsequent episodes,

00:11:11.340 | we'll speak about exactly how sleep harnesses

00:11:14.660 | and improves our emotional and mental health

00:11:16.780 | and how it falls apart when we don't.

00:11:19.100 | So that's how it certainly is emerging biologically.

00:11:24.100 | And that's how we as a society

00:11:26.500 | respect that and accommodate that.

00:11:28.900 | And then probably by the age of starting school,

00:11:34.020 | so sort of five or six,

00:11:35.540 | now we're starting to see fully monophasic sleep,

00:11:39.660 | children sleeping long bouts at night,

00:11:42.140 | and then being able to sustain wakefulness during the day.

00:11:46.060 | At that point, you have locked in your monophasic pattern,

00:11:50.300 | and that will continue throughout adulthood

00:11:53.300 | and into old age with a few caveats that we'll speak about.

00:11:58.220 | So that's how sleep unfolds

00:12:00.740 | in the monophasic, biphasic, polyphasic sleep

00:12:04.460 | across the lifespan.

00:12:06.340 | It doesn't quite tell you, however,

00:12:08.660 | how those different stages of sleep

00:12:11.220 | change across the lifespan.

00:12:12.660 | So I've shown you the view of sleep across the lifespan

00:12:17.220 | through one lens of the microscope.

00:12:19.220 | If we click down one lens

00:12:21.300 | and focus more deeply on the different stages of sleep,

00:12:25.500 | there we see a fascinating story.

00:12:27.540 | In utero, for the most part,

00:12:31.740 | you are in a sleep-like state as a fetus

00:12:35.820 | once you get to a certain point of development.

00:12:39.860 | In utero, that sleep-like state

00:12:43.100 | seems to be more so something that looks like REM sleep.

00:12:45.940 | Now, it's not fully-fledged, full-fat REM sleep yet,

00:12:49.900 | but it seems to be something very much like REM sleep.

00:12:52.700 | I say this because in the first episode,

00:12:57.220 | I told you as we go into REM sleep

00:12:59.620 | and we start to, as adults, dream,

00:13:02.140 | the brain paralyzes the body

00:13:04.020 | so that the mind can dream safely.

00:13:06.540 | Those kicks and those punches and those elbows

00:13:09.340 | that a mother will feel from the fetus

00:13:14.220 | seem to be during this dream state often,

00:13:17.500 | and I don't want to shatter any illusions

00:13:20.060 | of you start singing or you're cooing

00:13:22.380 | and you get these bumps and these elbows

00:13:24.180 | and these legs kicking and it's beautiful.

00:13:26.740 | It is beautiful,

00:13:28.060 | but it turns out that it's probably the REM sleep state,

00:13:31.380 | but the muscle sort of paralysis has not yet developed.

00:13:36.380 | So you're getting these electrical bursts,

00:13:38.940 | this frenetic activity of REM sleep that we described,

00:13:42.500 | but you're not getting any of the blockade

00:13:44.940 | of the motor output.

00:13:47.020 | And so it expresses itself as these kicks and these bumps.

00:13:49.900 | And then during the first six months of life,

00:13:54.380 | and at that point in the first six months,

00:13:56.540 | those infants are sleeping

00:13:57.780 | anywhere between 14 to 17 hours a day.

00:14:02.060 | That's immense, isn't it?

00:14:04.140 | I mean, it's right up there.

00:14:05.540 | If you look across phylogeny

00:14:08.740 | and you ask, which is by the way, a fascinating topic.

00:14:11.060 | At some point, we should do a separate podcast

00:14:13.340 | on sleep across different species.

00:14:14.900 | 'Cause I know like me,

00:14:16.300 | you love the whole variety of species,

00:14:19.180 | but you've got elephants who will sleep

00:14:21.540 | as little as four hours.

00:14:23.100 | And then you've got the little brown bat

00:14:25.180 | who is the rock star of sleep.

00:14:27.900 | And it will sleep almost 17 to 18 hours a day.

00:14:31.740 | It nudges out the sloth in that sense.

00:14:34.820 | - Can I ask you a question about that little brown bat?

00:14:36.700 | - Yeah.

00:14:37.540 | - Does it sleep hanging upside down?

00:14:39.100 | - It does.

00:14:39.940 | - So it can't have sleep paralysis in its little claws.

00:14:43.140 | - So it will not have that paralysis,

00:14:46.420 | but it goes through the stages of sleep very quickly.

00:14:49.900 | And this happens with birds as well.

00:14:52.180 | So birds that flock on a branch, they will sleep.

00:14:56.780 | And they sleep in some fascinating ways.

00:14:58.940 | Sometimes with one half of the brain,

00:15:00.500 | sometimes with both halves.

00:15:01.860 | But then you say, well, if I'm on a branch

00:15:04.460 | and there's this wonderful force

00:15:06.460 | called gravity underneath me and I go into REM sleep

00:15:09.300 | and I have that muscle paralysis, which they do,

00:15:12.300 | how does that work?

00:15:13.340 | Well, they only have very brief REM sleep periods

00:15:16.580 | that last just for a few seconds.

00:15:18.300 | And then they regain their muscle tone.

00:15:20.620 | - Got it.

00:15:21.460 | - Couldn't help but ask.

00:15:22.580 | - It's genius, isn't it?

00:15:23.940 | - The flora and the fauna.

00:15:25.060 | - Oh, I love, don't get me started with that.

00:15:26.340 | - But especially that the fauna enchant me that much.

00:15:29.420 | So I don't wanna draw us off course,

00:15:30.860 | but now we know that they can,

00:15:32.580 | that's why the bats don't fall.

00:15:33.940 | That's why the birds don't fall.

00:15:34.980 | - Correct, got it.

00:15:36.700 | So when you are then as an infant sleeping 14 to 17 hours,

00:15:41.700 | what's happening with those different stages of sleep,

00:15:44.300 | non-REM and REM?

00:15:45.620 | At that point, we can't really define

00:15:47.380 | and separate the different stages of non-REM

00:15:49.620 | because it's not yet fully formed.

00:15:52.820 | But we have what looks like a REM sleep active state

00:15:55.820 | and a deep non-REM sleep passive state.

00:15:59.420 | Almost 50% of the time that an infant and newborn is asleep

00:16:04.420 | is spent in REM sleep.

00:16:06.700 | Why do I say that with some kind of wonder in my voice?

00:16:10.140 | Because as adults, we're perhaps down to maybe 20%

00:16:15.140 | of our time spent asleep is in REM sleep.

00:16:18.300 | But 50% of the time when an infant is asleep,

00:16:22.460 | they are in REM.

00:16:24.260 | Why would this be the case?

00:16:25.860 | And across all species that have REM and non-REM,

00:16:28.780 | the time when we see REM sleep in highest volume amount

00:16:33.140 | is always after birth.

00:16:35.740 | There is something special about REM sleep

00:16:38.740 | and its function during that early period.

00:16:41.980 | And we now start to understand why.

00:16:44.620 | When you are first born,

00:16:46.340 | you are still going through a huge amount

00:16:49.260 | of brain maturation.

00:16:51.420 | And the recipe for the day there,

00:16:53.940 | unlike when we are teenagers,

00:16:56.660 | is exploding the brain with synapses,

00:17:00.100 | all of these connections throughout the brain.

00:17:03.580 | What we've discovered is that REM sleep acts

00:17:06.540 | as an electrical fertilizer to stimulate the growth

00:17:10.900 | of these connections within the brain.

00:17:13.180 | It's almost as though you could think about

00:17:14.620 | an internet service provider

00:17:16.420 | with this huge new neighborhood.

00:17:19.500 | And the first call of business is to go in

00:17:22.020 | and wire up each one of those homes

00:17:23.980 | with these fiber optic cables.

00:17:25.740 | That's what REM sleep is doing.

00:17:27.660 | And if you start to deprive,

00:17:31.380 | and these were studies, gosh, done many years ago

00:17:33.540 | by Howard Rothwalk and others,

00:17:35.340 | if you deprive animals of REM sleep,

00:17:37.740 | you stunt the developmental growth of the brain.

00:17:41.260 | - And presumably the whole animal.

00:17:42.820 | - And yeah, as a consequence.

00:17:44.740 | I mean, if you look at its social behavior,

00:17:47.100 | even just that, it's profoundly abnormal

00:17:49.820 | because you don't have that REM sleep developed brain.

00:17:53.860 | I mentioned this not because there is any causal evidence,

00:17:56.580 | but we have seen REM sleep impairments

00:17:59.700 | in certain developmental disorders,

00:18:01.740 | such as autism, as well as ADHD.

00:18:05.940 | I don't think there is any supportive evidence yet

00:18:08.820 | to come out with a claim that part of the trajectory

00:18:12.460 | underlying those conditions is abnormalities of REM sleep,

00:18:16.020 | but it's a very active area of research.

00:18:19.420 | So it's a fascinating time though, during infancy,

00:18:22.540 | when you get these huge amounts of REM sleep.

00:18:25.300 | Why?

00:18:26.140 | Because of what we call synaptogenesis,

00:18:29.500 | which is simply the creation of synapses genesis.

00:18:34.140 | Then as you move from six months

00:18:36.900 | across the next 18 months, something odd happens.

00:18:41.340 | Total sleep time starts to decrease,

00:18:43.780 | REM sleep starts to decrease,

00:18:46.220 | but non-REM sleep actually increases,

00:18:48.900 | even though total sleep time is decreasing.

00:18:51.580 | And there's a strange peak in lighter stage non-REM,

00:18:55.780 | what we call stage two non-REM,

00:18:57.660 | and those sleep spindles that I was describing

00:19:00.780 | in the first episode, these bursts of electrical activity.

00:19:04.380 | We will speak about the role of those sleep spindles

00:19:08.340 | in improving motor skill learning.

00:19:10.300 | And we've done many, many years of work in this area.

00:19:13.780 | Why is that relevant to this phase of life?

00:19:16.460 | That's right around the time when infants

00:19:19.260 | start to coordinate their limbs in a skilled way

00:19:22.700 | and begin to walk.

00:19:24.620 | And we believe that it is part of the process

00:19:27.100 | of the development of the motor system,

00:19:29.620 | enabling walking to begin.

00:19:31.780 | Amazing.

00:19:32.900 | So then things will change further,

00:19:35.580 | sleep time continues to decrease.

00:19:37.740 | And by about age five or six,

00:19:41.180 | now the cocktail blend of non-REM and REM

00:19:46.100 | is down to a stable ratio that will remain

00:19:48.700 | throughout the lifespan, which is a four to one ratio.

00:19:51.620 | So about 20% of the time that you're asleep

00:19:55.980 | will be REM sleep.

00:19:57.620 | And the remaining time will be,

00:19:59.820 | 80% of that time will be non-REM sleep.

00:20:02.460 | Provided one is getting sufficient total amounts of sleep.

00:20:05.660 | Correct, and getting it at the right moments in time

00:20:08.700 | that we described in the first episode,

00:20:10.780 | getting that sort of that appropriate chronotype match

00:20:14.620 | to the 24 hour clock,

00:20:16.620 | that will certainly alter those things too.

00:20:19.380 | So that's how sleep unfolds both at the first level

00:20:23.540 | of the lens, monophasic, biphasic, polyphasic,

00:20:27.820 | and then double clicking how the different stages

00:20:30.820 | of sleep unfold and what the reasons are behind that.

00:20:34.260 | I then said, once we're adults, we become monophasic.

00:20:39.260 | Yes, to a degree, but there is some contention

00:20:44.140 | about the way that we sleep in modernity,

00:20:47.060 | that we may not be sleeping in the way

00:20:50.260 | that we were designed to sleep,

00:20:52.140 | which brings us back to biphasic sleep.

00:20:55.380 | In the first episode,

00:20:56.660 | we spoke about this strange afternoon dip in our alertness

00:21:00.540 | that happens called the postprandial dip.

00:21:03.580 | And it happens somewhere between the one to 4 p.m. region,

00:21:06.660 | and it's measurable,

00:21:07.740 | and it seems to be biologically wired into us.

00:21:12.260 | If you look at certain cultures

00:21:13.900 | that are not touched by modernity,

00:21:17.140 | so we know those have studied hunter-gatherer tribes,

00:21:21.660 | they don't quite sleep the way that we do.

00:21:24.060 | And they don't sleep the way that we do

00:21:25.580 | for at least two reasons.

00:21:27.380 | The first is that they will often have

00:21:29.860 | a siesta-like pattern of behavior,

00:21:32.420 | where especially in the hot, dry season,

00:21:35.180 | they will take a nap in the afternoon.

00:21:38.740 | In the wet, cooler season, that may not be the case,

00:21:42.420 | but they certainly have more of a biphasic pattern

00:21:45.420 | where they'll sleep longer at night

00:21:47.420 | and then have a short nap, siesta-like.

00:21:50.020 | And then of course,

00:21:50.860 | there are Latin and Mediterranean cultures,

00:21:52.860 | and they have this practice of the siesta-like behavior.

00:21:56.300 | Coming back to the hunter-gatherer tribes,

00:21:58.820 | the way that they also do not sleep

00:22:01.660 | in a similar manner to that which we do

00:22:03.900 | is their timing of sleep.

00:22:06.020 | They don't go to sleep as the sun goes down.

00:22:09.660 | They will usually, on average as a group,

00:22:11.860 | they will usually go to sleep about two hours after sundown.

00:22:15.820 | And then they will wake up, not with the rising of the sun,

00:22:20.420 | they wake up just before that.

00:22:22.140 | And you think, are they predictive of the light?

00:22:25.460 | No, the thing that changes first

00:22:28.460 | before the sun truly rises is temperature.

00:22:32.180 | And temperature is a very strong predictor

00:22:34.500 | that that forces them awake.

00:22:36.540 | So when you think about how they're sleeping then,

00:22:40.780 | consider the term midnight.

00:22:43.540 | Most of us never really think about what the term means.

00:22:47.300 | Midnight refers to the fact

00:22:49.700 | that it is the middle of the night.

00:22:52.820 | But for most of us in the modern world,

00:22:54.940 | that's the time when we're thinking about

00:22:56.300 | sending our last email or posting to social media.

00:22:59.660 | Midnight is no longer midnight for society,

00:23:03.660 | but it is for them.

00:23:04.780 | - So should we be thinking about midnight

00:23:08.620 | as the middle of the night in the context

00:23:10.820 | of the extreme early person, morning person,

00:23:15.100 | who presumably likes to go to bed around 8 p.m.,

00:23:19.900 | wake up around 4 a.m.?

00:23:21.100 | Most people hear 4 a.m. and they go, oh goodness,

00:23:23.580 | that's early.

00:23:24.420 | Sort of like the mighty Jocko Willink

00:23:27.100 | is famous for posting images of his digital watch.

00:23:32.140 | Usually I think it's 4.30 a.m., wake up,

00:23:34.060 | and that's when he starts his workout.

00:23:35.580 | So his Twitter, I guess they call it xnowfeed,

00:23:39.180 | and Instagram is replete with images of his watch, 4.30,

00:23:42.500 | and people think, goodness, that's early.

00:23:44.500 | He was a guest on this podcast, spoken to him before,

00:23:48.420 | but he goes to bed pretty early, most nights.

00:23:51.020 | So in some sense, midnight for him

00:23:55.460 | or for somebody with a similar schedule

00:23:56.780 | is truly middle of the night.

00:23:58.740 | But for the other chronotypes,

00:24:01.260 | for people that prefer to go to sleep

00:24:03.180 | or who naturally get sleepy around 10 or 11 p.m.

00:24:06.940 | or even later, how should they think about

00:24:10.060 | this biphasic, polyphasic business?

00:24:11.740 | Because at some level, we all have to reconcile

00:24:16.740 | our sleep schedule with the demands

00:24:19.020 | of work and family and so on.

00:24:20.380 | - That's right.

00:24:21.220 | So I was very specific when I said

00:24:23.460 | the hunter-gatherer tribes, on average,

00:24:26.180 | that's the way that they will sleep.

00:24:28.260 | But like the rest of society, there's a huge distribution.

00:24:32.660 | And there will be some proportion of them

00:24:35.020 | who are a little bit like Jocko,

00:24:37.700 | who will be on the early side of that,

00:24:39.980 | on the very early side of that.

00:24:41.620 | But then there are other people who are clear night owls,

00:24:44.940 | and they may not be going to bed until 10 or 11

00:24:49.380 | and waking up later.

00:24:50.940 | So there is a distribution there.

00:24:54.380 | You don't have to worry that my statement of midnight,

00:24:58.420 | on average, that does seem to be when we are dislocated

00:25:02.100 | from all of the trappings of modernity,

00:25:04.620 | how a group of representative humans on average will sleep.

00:25:09.620 | But there is huge, as I said, differences

00:25:12.900 | from one individual to the next.

00:25:14.580 | By the way, you can ask the question,

00:25:16.380 | why do we have these things called chronotypes?

00:25:19.180 | Why is there such variability

00:25:22.100 | in how people have a preference for when they sleep?

00:25:26.340 | Wouldn't it just be easier if biology designed us

00:25:30.380 | all to be asleep at the same time?

00:25:32.740 | Not so.

00:25:34.180 | We mentioned in the first episode

00:25:35.860 | that sleep is truly idiotic in the sense that,

00:25:39.020 | you know, you're not protecting yourself

00:25:41.460 | or the people that you care about.

00:25:44.380 | And if everyone slept at the same moment in time,

00:25:48.460 | you as a collective and as an individual

00:25:51.860 | would be vulnerable for an eight-hour period,

00:25:54.940 | seven to nine-hour period.

00:25:56.980 | But by way of this wonderful injection of variability

00:26:01.820 | as to preferences for when people sleep,

00:26:04.620 | maybe there are some people who are going to bed at 8 p.m.

00:26:07.780 | and there are other people and they're waking up at 4 a.m.

00:26:11.980 | There are other people who go to bed at midnight

00:26:14.060 | and wake up at 8 a.m.

00:26:15.940 | So then think about that.

00:26:17.700 | At some point, what you've done

00:26:19.540 | is that there will always be someone

00:26:21.940 | or a collection of people awake until midnight,

00:26:24.460 | and there will always be a collection of people

00:26:26.580 | who are awake starting at 4 a.m.

00:26:28.900 | So as an individual,

00:26:30.380 | everyone gets their eight-hour opportunity,

00:26:32.980 | but as a collective, as a clan,

00:26:36.340 | you've reduced your vulnerability down by 50%

00:26:40.260 | because Mother Nature injected the variability

00:26:43.060 | by way of genetics of chronotype to distribute that

00:26:47.100 | and lessen the burden.

00:26:48.980 | Does that make any sense?

00:26:50.020 | - It does.

00:26:50.860 | And it reminds me of how the circadian rhythm,

00:26:53.180 | which we discussed in episode one,

00:26:55.420 | is about 24 hours, not exactly 24 hours.

00:26:59.220 | The rhythm of the suprachiasmatic nucleus neurons

00:27:02.180 | that generate the circadian rhythm, as I recall,

00:27:04.860 | is rarely exactly 24 hours.

00:27:06.980 | It's 24.2 or 24.4.

00:27:09.820 | And the idea in mind, the just-so story,

00:27:13.180 | is that that variation allows for entrainment

00:27:17.580 | matching to the outside light-dark cycle,

00:27:19.300 | which changes across the year.

00:27:20.540 | So you don't want it rigidly 24 hours

00:27:24.140 | because if there's any variation in light-dark,

00:27:26.340 | which of course there is,

00:27:27.740 | even at the equator across the year,

00:27:29.100 | there's subtle variations,

00:27:30.180 | but certainly as you move away from the equator.

00:27:31.940 | And so these variations in your circadian rhythm clock,

00:27:36.940 | SCN, suprachiasmatic nucleus, might be 24.2.

00:27:42.340 | Mine might be 24.6, someone else 24.1.

00:27:46.980 | And in that sense, allows some malleability

00:27:51.060 | to matching the circadian rhythm

00:27:53.580 | to outside light-dark rhythms.

00:27:55.100 | Is that a decent parallel for what we're talking about here?

00:27:58.220 | - It is, it's a beautiful demonstration

00:27:59.660 | that there is always some,

00:28:02.260 | it's almost wiggle room in how biology is programmed

00:28:07.260 | because some degree of noise,

00:28:11.020 | almost stochastic noise, can be very beneficial.

00:28:14.980 | And it's much more predictive

00:28:17.060 | of the way in which the world works.

00:28:18.900 | And it's much more adaptive for a species to enact

00:28:23.380 | and to embrace that kind of variability.

00:28:26.100 | And yours was a beautiful example

00:28:28.580 | that it's about 24 hours,

00:28:31.300 | but it's certainly responsive to changes

00:28:34.100 | in light duration across the year.

00:28:36.460 | And it has to be because we need to buckle ourselves

00:28:39.940 | to the light-dark cycle for optimal survival.

00:28:43.500 | And here's another demonstration

00:28:45.660 | of where it's not about the circadian rhythm,

00:28:47.900 | but it's about the chronotype distribution,

00:28:51.980 | not within an individual across the year,

00:28:55.700 | but across individuals at any one moment in time.

00:29:00.020 | And that variability, once again,

00:29:02.020 | provides a biological benefit.

00:29:05.140 | - In the first episode, and again, now,

00:29:09.500 | you were discussing chronotypes.

00:29:10.900 | And one thing that I've meaning to ask

00:29:13.180 | is you said that chronotype is genetically determined,

00:29:17.380 | but does that necessarily mean it is directly inherited

00:29:20.940 | from mom and/or dad?

00:29:22.980 | Meaning if your parents are both extreme

00:29:26.140 | early morning types,

00:29:27.060 | will you grow up to be an extreme early morning type?

00:29:29.980 | You already established that during infancy

00:29:31.820 | and development, adolescence, et cetera,

00:29:34.340 | that our chronotype is somewhat masked

00:29:37.820 | by some of the developmental necessities.

00:29:42.820 | But once we reach young adulthood

00:29:44.540 | and our chronotype has been established,

00:29:46.940 | can we look to our parents to determine

00:29:50.580 | whether or not we are more likely

00:29:52.380 | to be a morning person or a late shifted?

00:29:55.940 | - It's very unlikely to find anyone

00:29:59.180 | whose parents were both extreme morning types,

00:30:03.140 | who is a neutral or an evening type,

00:30:06.340 | and vice versa.

00:30:08.020 | So my guess is that people with,

00:30:11.700 | if they know of their biological parents

00:30:13.700 | and they know of their rhythms,

00:30:15.540 | it's highly likely that you will at some point acquiesce

00:30:20.540 | in your lifetime to being very similar to them.

00:30:24.220 | Now, there are certain life conditions and contexts

00:30:27.220 | where you can fight that.

00:30:30.180 | If you're someone who is in punk rock band

00:30:36.020 | and you're touring all the time,

00:30:38.140 | even though your mom and dad may be morning types

00:30:40.740 | and you may be a morning type,

00:30:42.700 | you're on the road, you're playing gigs,

00:30:44.540 | there's no chance.

00:30:45.780 | But at some point, let's say you retire

00:30:48.980 | and you give yourself the opportunity

00:30:51.700 | to express your natural rhythm,

00:30:53.220 | you will go back to that.

00:30:54.380 | So yes, it's highly genetic.

00:30:56.620 | It's not entirely genetic.

00:30:58.740 | There is some degree of modification

00:31:02.260 | that happens on the basis of context.

00:31:04.340 | And I've just given you a good example of context

00:31:06.980 | and also your exposure to light.

00:31:09.220 | You can be someone who is, let's say a neutral like me,

00:31:12.860 | but if you're constantly invaded by electric light at night,

00:31:17.140 | you're drinking too much caffeine

00:31:19.220 | and you're on your laptop and your computer and your phone

00:31:22.900 | and you're always activated by social media,

00:31:26.380 | it's very easy for someone like me to drift

00:31:29.700 | and become a 1 a.m. to 9 a.m. person.

00:31:34.700 | That's not my natural type,

00:31:36.580 | but context and the environment have shifted me.

00:31:40.180 | But for the most part, yes to your question.

00:31:42.580 | - I'd like to take a brief break

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00:32:55.700 | - Okay, so getting back

00:32:56.660 | to these different phase opportunities for sleep,

00:33:00.980 | clearly I'm getting the language wrong here,

00:33:02.460 | but monophasic, biphasic, and polyphasic.

00:33:07.220 | Could you give us a few more examples

00:33:10.260 | of different types of biphasic and polyphasic sleep?

00:33:14.260 | - So coming back to biphasic sleep,

00:33:16.980 | I described one version once we are adults,

00:33:19.900 | which is the siesta-like notion,

00:33:22.420 | one long bout at night, short about during the day.

00:33:25.620 | And that bout during the day is usually matching

00:33:29.380 | that drop in alertness that we described.

00:33:32.180 | It sort of hits that sweet spot right there.

00:33:34.380 | And it's quite easy for some people

00:33:36.380 | to fall asleep in that period.

00:33:37.980 | - Between, somewhere between one and 4 p.m.

00:33:40.140 | - One to four, yeah.

00:33:40.980 | And I know it's a large window,

00:33:42.540 | but that just allows us to sort of know,

00:33:45.340 | okay, if you're someone like yourself,

00:33:47.020 | who's a morning type,

00:33:49.300 | you would probably start to want to nap

00:33:51.060 | a little bit earlier if you were biphasic.

00:33:53.300 | Someone like me, a neutral, probably an hour and a half,

00:33:56.500 | two hours later still.

00:33:57.900 | But there is a different version of biphasic sleep

00:34:02.100 | for adults that has been described in the literature.

00:34:05.700 | And it's fascinating, but I don't think it's biological.

00:34:09.780 | It's the notion that some people will have heard

00:34:11.980 | called first sleep, second sleep.

00:34:14.980 | And now you are splitting your sleep into two phases,

00:34:18.660 | but they're split across the night.

00:34:21.020 | So the idea is that you fall asleep

00:34:24.380 | and you'll maybe have four-ish hours,

00:34:28.020 | and then you wake up and you then are awake

00:34:32.860 | for several hours, and then you go back to sleep

00:34:35.780 | for another three or four hours.

00:34:37.940 | If you look in history, in the record of human history,

00:34:43.420 | it's very clear that there were some cultures doing this,

00:34:46.580 | particularly if you look at some of the European cultures,

00:34:49.940 | Great Britain in particular, there is good evidence

00:34:52.620 | that somewhere between about the 15th to 19th century

00:34:56.540 | seems to have ended during the kind of Dickensian era.

00:34:59.700 | People were describing this behavior

00:35:03.300 | and they would wake up in the middle of the night

00:35:05.580 | after about four hours, they would make food,

00:35:08.060 | they would play music, they would write,

00:35:10.020 | they would make love.

00:35:11.340 | It was a real thing.

00:35:13.660 | And I'm not suggesting that it did not happen.

00:35:16.140 | It clearly did, and there's a great book that outlines this.

00:35:19.900 | But is it the way that we were designed to sleep,

00:35:23.940 | biphasically versus the siesta-like?

00:35:26.580 | And I don't think it is.

00:35:28.460 | There is no good collection of evidence.

00:35:32.540 | If you look at the biology of our human rhythms

00:35:36.420 | that argues that there is this magical period

00:35:39.180 | of a huge spike in our circadian rhythm that happens

00:35:42.740 | right in the middle of the night that should force us awake.

00:35:46.740 | There is one paper that's often cited for this.

00:35:49.820 | And in truth, that paper, if you read it,

00:35:51.940 | says nothing about first sleep, second sleep,

00:35:54.500 | doesn't speak about biphasic sleep at all.

00:35:58.180 | And that paper I think is unfairly used

00:36:02.260 | as a justification of first sleep and second sleep.

00:36:05.380 | And the paper to me has at least three problems.

00:36:08.660 | It's a great paper.

00:36:10.540 | There's no problem with the paper and its hypothesis,

00:36:13.380 | but its use as justification for first sleep,

00:36:16.700 | second sleep has three problems.

00:36:18.340 | The first is the artificial nature of the study.

00:36:22.100 | They weren't designing it to test the hypothesis,

00:36:24.460 | but they had individuals in bed for 14 hours straight

00:36:28.100 | relative to a standard eight-hour period.

00:36:31.020 | And sure enough, what they found was that

00:36:33.340 | when you force people night after night

00:36:35.380 | to be in bed for 14 hours,

00:36:38.300 | somewhere after about six or seven hours, they wake up.

00:36:42.780 | And then you can't get out of bed in the study.

00:36:46.340 | So you just lie awake.

00:36:47.940 | And then at some point, I don't know if it's through boredom

00:36:51.100 | or you drift back off into sleep.

00:36:53.700 | And that was argued as a clear demonstration

00:36:55.940 | of this split sleep.

00:36:57.740 | But as I said, they're awake usually

00:36:59.340 | for about six and a half, seven hours.

00:37:01.540 | Also, there was no magical awakening period.

00:37:06.580 | It's a probability distribution.

00:37:08.620 | And what that means is if you look at the data,

00:37:11.420 | it's just more likely that people will wake up

00:37:14.580 | after about six or seven hours,

00:37:16.180 | and then more likely that they will go back down into sleep.

00:37:18.820 | It wasn't as though the whole experiment

00:37:21.060 | demonstrated a very clear termination of sleep

00:37:23.900 | that everyone had at that moment in time.

00:37:26.740 | So that's the first issue.

00:37:29.260 | And the second issue, which is first issue,

00:37:31.340 | it's kind of an abnormal thing, 14 hours forced in bed.

00:37:34.900 | The second is it wasn't a clear separation.

00:37:37.020 | It's just simply higher probability.

00:37:39.460 | The final issue is that it was a study done

00:37:42.540 | in only seven individuals, healthy males.

00:37:45.900 | And so I have yet to see it scaled up.

00:37:49.460 | Did it happen, first sleep, second sleep?

00:37:52.940 | Yes, it did.

00:37:53.900 | Is there any strong evidence

00:37:55.260 | that that's how we naturally were designed

00:37:58.260 | and have evolved to sleep?

00:38:00.900 | In truth, I don't think so.

00:38:02.540 | At least I don't see good evidence right now

00:38:04.500 | of supporting that, but remain open to it.

00:38:07.380 | - In episode one, we talked a little bit

00:38:09.220 | about body position during sleep

00:38:11.460 | and how different degrees of incline or decline

00:38:16.340 | might impact some of the features of sleep.

00:38:18.340 | And I can't help but ask now,

00:38:19.620 | as you describe this biphasic pattern

00:38:23.300 | for people that were essentially

00:38:25.660 | experimentally restricted to the bed,

00:38:28.260 | is there something about being horizontal

00:38:31.620 | that makes us sleepy?

00:38:33.580 | - There is.

00:38:34.700 | And it's perhaps not for the reasons that you would think,

00:38:38.140 | which is, okay, I'm just pre-programmed

00:38:41.180 | when I lie down and my head hits the pillow.

00:38:43.540 | It turns out that it seems to be temperature,

00:38:46.900 | that when your body is recumbent, lying flat horizontal,

00:38:51.900 | the distribution of how your body is able

00:38:55.700 | to move blood around the different regions

00:39:00.380 | and decrease your core body temperature,

00:39:03.100 | meaning it can push blood, warm blood,

00:39:05.700 | out of the core of your body to these surface areas.

00:39:10.300 | And when you push it out to the surface areas,

00:39:13.260 | you release that heat.

00:39:14.860 | It's this huge thermal dissipation that happens

00:39:17.580 | when we move blood out of the core to the surface,

00:39:20.340 | you emit that heat,

00:39:21.580 | and your core body temperature plummets.

00:39:23.460 | When your body temperature,

00:39:24.700 | your core body temperature decreases,

00:39:27.340 | you have a higher likelihood of sleepiness.

00:39:30.580 | In fact, it's very difficult for you

00:39:32.620 | to fall asleep if your core body temperature does not drop.

00:39:36.500 | And by lying down, the body's,

00:39:39.300 | what we call vasoactive ability to distribute that blood

00:39:44.300 | in a way that is permissive for thermal dissipation

00:39:48.580 | of core body temperature is superior.

00:39:51.460 | And that's the reason why we find it easier

00:39:54.260 | to fall asleep lying down than let's say semi-recumbent

00:39:58.660 | or certainly propped all the way up.

00:40:01.140 | And it's probably the reason naturally we evolved

00:40:03.980 | just to lie down on the floor.

00:40:06.620 | - Very interesting.

00:40:07.620 | Maybe now's a good time to talk about biphasic sleep

00:40:13.060 | in the context of about of sleep at night

00:40:16.780 | and the afternoon nap.

00:40:18.620 | You've mentioned this postprandial dip

00:40:20.500 | that most people experience between one and 4 p.m.

00:40:23.740 | that many people try and combat with caffeine.

00:40:25.940 | We will also talk about caffeine this episode.

00:40:29.900 | It's such an interesting substance.

00:40:31.620 | And I think the most commonly used drug,

00:40:35.620 | 'cause it is a drug after all, worldwide,

00:40:37.700 | I think more than 90% of adults worldwide

00:40:41.260 | consume caffeine on a daily basis.

00:40:43.060 | - That's correct.

00:40:43.900 | And I believe it is after oil,

00:40:46.700 | it may be perhaps the second

00:40:49.780 | or at least the third most traded commodity on this planet.

00:40:53.620 | And it is what we call a psychoactive stimulant.

00:40:57.260 | It is a stimulant.

00:40:58.460 | And it's probably one of the only stimulants

00:41:00.300 | that we will readily give to our children

00:41:03.340 | and not be too concerned about it.

00:41:07.180 | - We'll get to caffeine in depth

00:41:08.860 | a little bit later in this episode,

00:41:10.700 | but I can't help but just mention that someone,

00:41:13.460 | I think it was Michael Pollan said that,

00:41:15.340 | "Caffeine is one of the few drugs

00:41:16.860 | "that almost everybody takes

00:41:18.380 | "just to quote unquote feel normal."

00:41:20.940 | - Yeah, exactly.

00:41:23.540 | I think sometimes sleep deprivation

00:41:26.020 | is simply just the absence of caffeine.

00:41:30.620 | And so it's a very interesting chemical,

00:41:34.780 | which I have in truth changed my mind on.

00:41:37.900 | And I'm happy to speak about why I've changed my mind,

00:41:40.980 | but also some guardrails too.

00:41:44.020 | - And we'll go there.

00:41:45.780 | Meanwhile, I'll take a sip of my triple espresso here

00:41:49.340 | as we discuss naps.

00:41:53.180 | Are naps good for us?

00:41:54.300 | Should we nap?

00:41:55.780 | What if we don't like naps?

00:41:57.020 | Why do we wake up from naps groggy sometimes

00:41:59.940 | and other times we feel refreshed?

00:42:02.100 | Tell us about napping.

00:42:03.700 | - Naps are both good and bad depending on the situation.

00:42:09.980 | Naps can be a double-edged sword in other words.

00:42:14.300 | We and others have done lots of studies on naps

00:42:18.140 | and the benefits are fascinating and stunning.

00:42:21.780 | I'll tell you about one study we did.

00:42:23.860 | We had participants assigned to one of two groups

00:42:27.220 | and at midday they all learned a whole list of new facts.

00:42:30.780 | So it was a study about learning and memory.

00:42:33.580 | And then one group took a 90 minute sleep opportunity,

00:42:37.180 | sort of focused right around that drop in alertness.

00:42:40.460 | The other just remained awake lying on a bed

00:42:43.220 | and they just watched a nature documentary.

00:42:46.860 | And then five hours later,

00:42:49.900 | we had them do another learning session.

00:42:54.020 | And so they've woken up after the 90 minute nap,

00:42:56.540 | they've got through that sort of initial lull

00:42:58.540 | that we'll discuss what that is after you wake up.

00:43:02.100 | Everyone's now back to operating temperature.

00:43:05.180 | So in other words,

00:43:06.020 | I've had you try to cram in a whole list of facts at midday

00:43:10.060 | and then a whole list of facts, new facts again at 5 p.m.

00:43:13.820 | And I can ask,

00:43:14.860 | what is the learning capacity of your brain at midday

00:43:18.180 | and at 5 p.m.?

00:43:19.980 | And is there any difference in your learning ability

00:43:23.300 | when you have had a nap in between versus not?

00:43:26.860 | And sure enough,

00:43:27.700 | what happened in the group that did not nap,

00:43:29.860 | their learning capacity gradually declined across the day.

00:43:33.820 | The nap group,

00:43:35.740 | they were able to sustain their learning.

00:43:37.860 | And in fact, if anything, improve it.

00:43:40.100 | And the difference between those two groups at 5 p.m.

00:43:43.380 | was about 20%.

00:43:45.580 | So that's certainly non-trivial in terms of,

00:43:48.020 | if you to say, here's a new compound

00:43:50.540 | that can boost your learning capacity by 20%,

00:43:53.500 | would you take it?

00:43:54.420 | I suspect it would probably make some money.

00:43:57.420 | So that's a demonstration of full learning and memory.

00:44:00.660 | We did another study very much like that

00:44:02.460 | in terms of its design,

00:44:03.500 | but we looked at your emotional brain

00:44:06.260 | and we were showing people different types

00:44:09.380 | of emotional expressions and having them rate them.

00:44:13.500 | And we did that firstly before a nap

00:44:15.300 | and then after a nap versus that same time

00:44:20.220 | in sort of midday versus 5 p.m.

00:44:23.100 | And another group did not nap.

00:44:24.900 | And sure enough, the group that did not nap,

00:44:27.340 | by about 5 p.m.,

00:44:28.900 | they were starting to rate fearful faces and angry faces

00:44:32.780 | as much more fearful and much more angry.

00:44:36.180 | But if you looked at the group that napped,

00:44:38.140 | it was different.

00:44:39.780 | They actually lessened the response to fear

00:44:44.660 | and they blunted the normal increase

00:44:47.780 | in anger sensitivity across the day.

00:44:51.140 | And the nap seemed to boost

00:44:53.660 | how positively you rated happy faces.

00:44:57.540 | So a nap there had the ability

00:45:00.620 | to reset the magnetic north of your emotional compass.

00:45:05.580 | And there was a beneficial, almost added rose tint

00:45:09.620 | to your worldview glasses after you'd napped.

00:45:13.660 | What was also interesting in those two studies,

00:45:15.660 | two different types of sleep

00:45:16.980 | were transacting those benefits.

00:45:18.860 | In the nap group that was doing the learning,

00:45:22.300 | the learning benefit that they got

00:45:24.300 | wasn't just about them napping and sleeping.

00:45:26.420 | It was about them having these sleep spindles.

00:45:29.220 | The more of those sleep spindles that you had,

00:45:31.460 | the greater the restoration of your learning capacity

00:45:34.780 | when you wake up.

00:45:36.620 | For the emotional recalibration that I described in the nap,

00:45:39.980 | that had nothing to do with sleep spindles

00:45:41.940 | or even non-REM sleep.

00:45:43.620 | It required REM sleep to produce that benefit.

00:45:47.820 | So there are certainly many benefits

00:45:50.100 | and we've looked downstairs in the body,

00:45:52.300 | blood pressure, cardiovascular measures, immune health,

00:45:55.780 | they all seem to benefit.

00:45:57.620 | So at that point, everyone may be thinking,

00:46:00.500 | of course, this sounds good.

00:46:01.820 | Not to mention the basics,

00:46:03.420 | which is your attention, your concentration,

00:46:06.340 | your focus and your energy all improve by way of naps.

00:46:10.180 | Even your decision-making.

00:46:11.500 | - You said decision-making.

00:46:12.700 | - Yeah, even your decision-making is improved.

00:46:15.220 | So your capacity to make the correct decisional outcomes

00:46:19.340 | based on this weight of evidence that you're facing,

00:46:22.540 | that's also improved.

00:46:23.780 | So almost all areas of cognition that we've looked at

00:46:27.820 | and many areas of your emotional and mood health

00:46:30.740 | we've looked at seem to benefit by way of a nap.

00:46:34.620 | At that point you're thinking, so then what's the problem?

00:46:38.380 | The problem is that when you nap,

00:46:42.580 | you release some of that sleep pressure

00:46:45.500 | that's been building up.

00:46:46.420 | So in the first episode,

00:46:47.900 | we spoke about a chemical called adenosine.

00:46:50.620 | And the longer that you're awake,

00:46:52.060 | the more adenosine that builds up.

00:46:54.180 | The more adenosine that builds up,

00:46:55.860 | the sleepier you will feel.

00:46:58.100 | And after about 16 hours of being awake,

00:47:00.340 | you should have lots of healthy sleepiness

00:47:02.420 | of adenosine in your brain to put you asleep

00:47:04.940 | and keep you asleep.

00:47:06.900 | And when we sleep,

00:47:08.100 | we are able to clear that adenosine from the brain.

00:47:10.980 | So we wake up after seven to nine hours.

00:47:13.420 | And if it's been good quality sleep,

00:47:15.340 | we're refreshed because we've cleansed the brain

00:47:17.500 | in part of that adenosine.

00:47:19.140 | When you take a nap,

00:47:21.500 | like a pressure valve on a steam cooker,

00:47:26.020 | you just release some of that healthy sleepiness

00:47:29.300 | that you've been building up.

00:47:30.940 | So the dark side of napping

00:47:34.260 | is if you are struggling with sleep

00:47:36.820 | and you suffer from insomnia,

00:47:39.140 | the advice is do not nap during the day

00:47:42.340 | because you're setting yourself up

00:47:43.820 | for an even higher probability of failure at night.

00:47:46.740 | Why?

00:47:47.580 | Because when you nap,

00:47:48.740 | you release some of that good sleepiness

00:47:50.860 | that we need to build up for you

00:47:52.940 | as someone who is struggling with sleep

00:47:54.780 | to give you the greatest chance

00:47:56.060 | of a weight of sleepiness on your shoulders.

00:47:59.460 | So if you are not struggling with sleep

00:48:01.500 | and you can nap regularly,

00:48:02.980 | I would say naps are just fine

00:48:05.020 | and we can unpack what is an optimal nap

00:48:07.660 | and the protocol for what napping should be.

00:48:10.420 | I would say that's great.

00:48:13.220 | The only caveat is make sure

00:48:15.740 | that you're not napping too late into the day.

00:48:18.420 | And this is one of the components

00:48:20.020 | of the protocol of how to nap

00:48:22.540 | because napping late in the day is too close to sleep.

00:48:26.900 | And you can think of it

00:48:28.380 | almost like snacking before your main meal.

00:48:32.100 | A nap late in the day

00:48:33.180 | just takes the appetite edge off your sleepiness

00:48:36.540 | so that when it comes time for sleep,

00:48:38.180 | you're not as hungry anymore.

00:48:40.460 | So just keep that in mind,

00:48:42.300 | but we can unpack perhaps the optimal way to nap

00:48:46.700 | if you are going to nap

00:48:48.380 | and exactly the do's and the don'ts of that

00:48:51.460 | if that sounds of somewhat interest.

00:48:54.380 | - That is of immense interest to me

00:48:57.540 | and I know many other people.

00:48:58.660 | I'm a huge believer in naps.

00:49:00.340 | I've always enjoyed short naps of about 10 to 30 minutes

00:49:05.180 | unless I'm somehow sleep deprived,

00:49:06.820 | in which case I will sleep for an hour

00:49:10.100 | or even a little bit more,

00:49:10.940 | but I make sure I set an alarm

00:49:12.860 | really based on advice that you gave me,

00:49:15.140 | which was to first of all,

00:49:17.580 | decide whether or not a nap is beneficial for me

00:49:21.460 | or for whoever is considering that.

00:49:24.100 | But then to make sure that however long that nap is,

00:49:27.700 | zero to 90 minutes,

00:49:29.500 | let it not be longer than 90 minutes

00:49:31.020 | because the real goal is to not disrupt nighttime sleep.

00:49:34.460 | - That's right.

00:49:35.300 | - Which is essentially just a more long-winded way

00:49:37.180 | of saying what you just said.

00:49:38.380 | So how does one determine the optimal duration of nap?

00:49:43.380 | And in particular to avoid the problem

00:49:48.740 | of disrupting nighttime sleep by napping,

00:49:51.300 | but also this rather common phenomenon

00:49:54.300 | of waking up and feeling kind of groggy

00:49:56.660 | or even kind of grumpy.

00:49:58.420 | I get the post-nap face,

00:50:00.260 | or we should call it the post-nap expression.

00:50:03.100 | - You need to trademark that.

00:50:03.940 | - The PNE, right, the PNE.

00:50:05.780 | What's your PNE?

00:50:06.620 | Do you wake up for morning too,

00:50:10.180 | some people wake up and they're like,

00:50:12.320 | that face, and then there's the like, good morning.

00:50:15.660 | You know, and I think people that wake up

00:50:16.900 | with a good morning are particularly delightful

00:50:19.020 | unless you're of the post-nap expression

00:50:21.660 | that is kind of the crumpled face,

00:50:23.380 | and then you just, you don't want to be around those people.

00:50:25.300 | - No, absolutely not.

00:50:26.620 | - Yeah, and this probably relates to spirit animals

00:50:30.380 | and things like that.

00:50:31.220 | Some people wake up like a cheerful chipmunk

00:50:33.700 | and other people seem to wake up like my bulldog Costello,

00:50:36.700 | where it's, you know,

00:50:38.060 | jowls still in contact with the floor.

00:50:40.860 | - Yeah, so PNE, I'm trying to hold it together

00:50:43.860 | and not absolutely just fall apart.

00:50:45.820 | It's brilliant, please trademark it.

00:50:48.100 | So firstly, to your question, how to optimally nap.

00:50:53.100 | The word optimal is interesting

00:50:56.260 | because when you, people say, how long should I nap?

00:50:59.980 | What's the optimal nap duration?

00:51:02.060 | The question I have back to them is,

00:51:04.380 | what are you trying to optimize?

00:51:06.620 | Because once I understand what you're trying to optimize,

00:51:09.900 | I can give you a better prescription,

00:51:12.980 | non-medical I'm talking about here,

00:51:14.820 | a better sort of, you know, protocol piece of advice

00:51:17.700 | for how to nap.

00:51:19.140 | I mentioned the study about emotional phases

00:51:21.420 | in part for a specific reason,

00:51:23.540 | 'cause I told you there the benefit came by way

00:51:25.900 | not of non-REM sleep, but REM sleep.

00:51:28.340 | And in our first episode,

00:51:29.580 | we said that when you go through these

00:51:31.540 | on average 90 minute cycles,

00:51:33.620 | you get most of your non-REM sleep first

00:51:36.220 | and then you'll have this bout of REM sleep at the end.

00:51:39.060 | And it always seems to go that way

00:51:40.860 | when you are a healthy, normal person.

00:51:42.900 | You go into non-REM sleep and then you go into REM sleep.

00:51:45.580 | It's very rare that you ever go directly into REM sleep.

00:51:48.540 | There are only two reasons when that seems to happen.

00:51:51.540 | The first is a clinical condition called narcolepsy

00:51:54.260 | where you can have sleep onset REM sleep

00:51:56.220 | and it's very rare.

00:51:57.500 | The second is if you are horrifically deprived of REM sleep

00:52:01.060 | night after night after night, I let you sleep then.

00:52:05.380 | At that point, REM sleep, the pressure for REM sleep

00:52:08.340 | has been built to the point of being almost just insatiable

00:52:13.820 | and your brain goes straight into REM sleep.

00:52:16.980 | But with those two things aside,

00:52:18.620 | you go into non-REM sleep first.

00:52:20.740 | So I brought up the emotional study

00:52:22.820 | of resetting your sort of mood compass

00:52:27.380 | because to get that REM sleep,

00:52:29.260 | you had to nap for a longer period of time

00:52:31.940 | because you had to get through the non-REM sleep first

00:52:34.940 | before you get the REM sleep.

00:52:37.740 | But let's come back to then assuming optimal is

00:52:41.740 | for most people when they speak about naps,

00:52:44.060 | I just want the quick reboot.

00:52:46.220 | I want my alertness and concentration which are failing

00:52:49.220 | because I'm staring at the screen

00:52:50.940 | or I just can't concentrate on the work that I'm doing.

00:52:54.340 | I want my alertness and my concentration to be improved.

00:52:57.180 | I want that sort of slight boost in brain energy

00:53:00.620 | where I know I can sustain myself for now

00:53:03.180 | along the period of time.

00:53:04.460 | And I've got the motivation, which is really in some ways

00:53:08.100 | how I like to think about energy as well.

00:53:10.500 | I've got the motivation, the drive to keep going,

00:53:12.500 | which is just starting to fail me.

00:53:14.260 | To get those basic things,

00:53:17.420 | which is what most people nap for,

00:53:19.580 | aim for a 20 minute nap.

00:53:22.060 | Why 20 minutes?

00:53:23.620 | If I thin slice the nap duration

00:53:26.340 | and those studies have been done

00:53:28.260 | where we look at essentially

00:53:29.260 | what's called a dose response curve.

00:53:31.020 | I give you five minutes of a nap, 10 minutes of a nap,

00:53:33.740 | 15 minutes, 20 minutes, 30 minutes, 45 minutes, 90 minutes.

00:53:38.660 | After five or 10 minutes, you don't really get very much.

00:53:42.780 | You will wake up and you'll have some degree

00:53:45.860 | of improved alertness and your basic reaction time

00:53:48.460 | may be a little bit quicker,

00:53:49.820 | but that fades very quickly

00:53:51.300 | and you don't sustain that benefit.

00:53:54.260 | Once you get past about 15 to 17 minutes,

00:53:58.100 | now things start to look different.

00:54:00.220 | You get these nice benefits

00:54:01.780 | for concentration alertness and motivation

00:54:05.020 | and those things sustain.

00:54:07.180 | So once you wake up out of that,

00:54:09.740 | probably really, I would say 20 minute nap.

00:54:12.380 | At that point, you've got some good wind

00:54:14.780 | in your concentration and energy sails for the brain

00:54:19.140 | and that will sustain you throughout the rest

00:54:21.860 | of the afternoon and into the evening.

00:54:24.180 | The benefit of the 20 minute nap

00:54:27.940 | is that you don't get the PNE,

00:54:32.180 | trademark Andrew Huberman.

00:54:35.540 | You don't get that almost sleep hangover.

00:54:39.020 | So some people will say, it's strange, I nap.

00:54:41.860 | Maybe I'll nap 45 minutes, 50 minutes and I wake up.

00:54:45.940 | And to be honest, Matt,

00:54:47.580 | I almost feel worse after the nap than I did before.

00:54:51.500 | And I don't understand it.

00:54:52.900 | It's something called sleep inertia.

00:54:56.700 | And an extreme version of this is in the first two hours

00:55:01.380 | of your night of sleep, you get a phone call

00:55:04.740 | or an alarm goes off and you wake up

00:55:07.980 | and you are just kind of lost in the ocean.

00:55:11.180 | You're looking around at your surroundings.

00:55:13.660 | You're just in this groggy state.

00:55:16.060 | You're half awake, half asleep.

00:55:17.540 | When you can respond and you can do things,

00:55:20.140 | but boy, does it feel miserable.

00:55:22.740 | And it's almost as though you're going

00:55:24.020 | from the ground floor right up to the penthouse suite,

00:55:27.660 | but you get stuck somewhere in between kind of floor 13

00:55:31.500 | and it's this rough state.

00:55:34.180 | If you go out into sleep, light stage one non-REM,

00:55:38.540 | then stage two non-REM.

00:55:40.780 | And just before you get into the very deeper stages

00:55:44.020 | of non-REM, three and four,

00:55:45.820 | that starts to happen around 30 to 40 minutes

00:55:48.980 | for most people.

00:55:50.780 | But by cutting your nap off at 20 minutes,

00:55:54.740 | you still get these nice benefits

00:55:56.340 | from a good chunk of healthy non-REM sleep,

00:55:59.100 | but you're not going so far into the cycle,

00:56:01.700 | so deep into your non-REM

00:56:04.100 | that when you wake up after 20 minutes,

00:56:06.780 | you're not in that what we call sleep inertia phase,

00:56:09.900 | that sleep grogginess, that sleep hangover phase.

00:56:12.940 | So it's a nice benefit that you get

00:56:14.740 | all of these improvements in your brain,

00:56:16.780 | but you wake up and very quickly

00:56:18.660 | you're back up to operating temperature

00:56:20.420 | and you don't suffer that inertia.

00:56:22.860 | Now that's not to say that when you sleep

00:56:24.980 | or you nap longer,

00:56:26.860 | you don't start to get more benefits, you do.

00:56:30.140 | And those benefits are both greater in their magnitude

00:56:34.100 | and sustain for a longer period of time, they do.

00:56:38.420 | It's just that you have to understand the trade-off

00:56:41.020 | that you will suffer,

00:56:41.980 | which is I will get more bang for my buck

00:56:45.700 | and I will get more benefits,

00:56:47.620 | but I will in the first sort of hour or so

00:56:51.460 | have to understand that at that point,

00:56:53.740 | I may even be functioning worse

00:56:56.100 | than that which I did before I even started napping.

00:57:00.380 | But if you're patient and you go through it,

00:57:02.980 | the rewards on the other side

00:57:05.100 | are significantly better still.

00:57:07.980 | So that's the first piece of advice.

00:57:10.020 | And when it comes to how to nap,

00:57:11.940 | I would say the dose and the timing make the poison

00:57:15.420 | and poison is hyperbole here.

00:57:19.060 | It's simply just the poison being

00:57:21.380 | how much sleep inertia you're going to suffer.

00:57:23.580 | So aim for about 20 minutes.

00:57:25.660 | That's the dose.

00:57:26.500 | The timing comes back to that which we described before.

00:57:29.820 | Do not nap too late into the day.

00:57:32.260 | So what's the rule of thumb here for a protocol?

00:57:35.100 | On average, for the average adult,

00:57:36.820 | I would say don't nap after about 3 p.m.

00:57:41.100 | 20 minute naps, sometime between 3 p.m.

00:57:45.500 | And if you're struggling with sleep, don't do this at all.

00:57:48.060 | If you're not and you're able to get to sleep fine,

00:57:51.500 | this seems to be a good ingredient

00:57:53.860 | for the basic return on your investment.

00:57:56.780 | Again, if you tell me what's the optimal nap duration,

00:58:01.540 | we need to have a conversation to understand

00:58:03.380 | what is it that you're going after here?

00:58:05.060 | What are the benefits?

00:58:05.980 | And then I can sort of create a finger buffet,

00:58:10.140 | kaleidoscope match to what you need,

00:58:12.380 | and we can think about the nap duration as a consequence.

00:58:15.780 | - Thank you.

00:58:16.620 | That's very informative.

00:58:18.180 | I have a colleague at Stanford who's a Howard Hughes

00:58:20.660 | investigator, which for those that don't know

00:58:22.580 | is a rather elite club of academic researcher.

00:58:26.420 | They have to essentially try out for it.

00:58:28.820 | They can, every five years they go up for renewal.

00:58:32.100 | It's a lot of money, which gives them a greater capacity

00:58:36.020 | to take on greater risk work, higher risk work.

00:58:39.260 | And he's also a member of the National Academy,

00:58:42.380 | and he was one of these people who graduated high school

00:58:44.220 | at 15 years of age, one of these phenoms.

00:58:47.740 | And he is so religious about his napping,

00:58:50.500 | such that when he travels to give seminars at other schools,

00:58:55.060 | he insists that they schedule a nap time

00:58:57.020 | for him after lunch.

00:58:58.420 | And in his office, you know, between 1230 and 1 p.m.,

00:59:03.420 | he's napping, everyone knows this.

00:59:05.060 | And I mentioned this because I think that oftentimes

00:59:08.300 | people think of the nappers as the lazy ones,

00:59:10.940 | but his output is near superhuman.

00:59:14.740 | And he attributes much of that output to the nap,

00:59:18.380 | not just the post-nap work that he's able to perform,

00:59:21.780 | but his ability to just kind of manage so many ideas.

00:59:25.820 | He has an enormous laboratory,

00:59:27.060 | and that's just one example.

00:59:28.180 | I think there are examples from sport,

00:59:29.660 | of sprinters taking naps on the side of the track field.

00:59:34.660 | I mean, so it seems that a capacity to nap

00:59:39.100 | is also something worth considering,

00:59:41.060 | because I think many people listening to this are thinking,

00:59:42.860 | well, I can't nap.

00:59:44.140 | Should I nap, you know?

00:59:46.260 | And can one teach themselves to nap?

00:59:49.060 | So that's the question,

00:59:50.460 | if one would want to explore napping.

00:59:52.740 | And is that something that one should even consider doing?

00:59:56.260 | If you don't have a propensity to nap, should you avoid it?

00:59:58.780 | If you want to try naps,

00:59:59.980 | how could one teach oneself to nap?

01:00:01.940 | You just mentioned earlier lying down

01:00:05.060 | relates to body temperature,

01:00:06.060 | body temperature relates to sleepiness.

01:00:08.940 | And then as a third question,

01:00:10.060 | I promise I'll repeat these if we need to.

01:00:12.260 | As a third question,

01:00:13.460 | I'd like to have a little bit of a discussion

01:00:15.420 | about some of the pseudo-nap states

01:00:18.660 | that I certainly am intrigued by.

01:00:20.740 | You know, for instance, just lying down

01:00:22.300 | and I'm doing a progressive bodily relaxation,

01:00:24.700 | things like yoga nidra, non-sleep deep rest,

01:00:27.420 | which is an acronym I coined

01:00:28.860 | simply to make it clear what I was talking about,

01:00:31.580 | but it's very similar to yoga nidra, things of that sort.

01:00:35.220 | In other words, put simply,

01:00:37.780 | should everyone think about having

01:00:40.020 | an early to mid-afternoon protocol

01:00:43.340 | to reset their cognition in their body?

01:00:46.380 | We call it a nap, but does it have to be a nap?

01:00:48.700 | And if we're not good nappers, should we try?

01:00:51.460 | And if so, how should we go about it?

01:00:53.420 | - Yeah, so to your three questions,

01:00:54.940 | firstly, if you're not a natural napper,

01:00:56.780 | should you start doing it?

01:00:59.100 | If you want to start doing it, how should you do it?

01:01:01.460 | And then the third is,

01:01:02.900 | is there some kind of, you know,

01:01:05.060 | substitute for a like kind,

01:01:08.300 | which would be these,

01:01:09.820 | I'd love the phraseology that you use,

01:01:11.940 | these liminal states.

01:01:13.820 | Do they mimic that?

01:01:15.980 | Are they different to that?

01:01:17.340 | How should we think about those?

01:01:19.340 | The first thing I would say to point number one,

01:01:21.620 | if you are not a natural napper,

01:01:24.580 | don't necessarily force yourself to be.

01:01:26.820 | As long as you're getting the sleep

01:01:28.180 | that you feel you need at night,

01:01:29.980 | and you feel refreshed and restored during the day,

01:01:32.900 | and you don't have that sort of postprandial drop

01:01:35.980 | to the point of thinking,

01:01:37.340 | I almost need to nap during the day.

01:01:39.660 | There is no pressure,

01:01:40.940 | based on anything I've been telling you,

01:01:42.940 | for you to start napping,

01:01:44.700 | nor should there be any reason that you do start napping.

01:01:47.940 | But let's say that you want to try.

01:01:49.620 | What would be the right protocol

01:01:51.140 | to improve and increase the likelihood?

01:01:56.060 | The best way you can do this

01:01:57.820 | is to mimic nighttime as best you can.

01:02:02.500 | So wherever you are, if you can,

01:02:04.860 | shut off the lights,

01:02:07.100 | make sure that you can block out curtains, blinds.

01:02:12.020 | If you can't do that fully,

01:02:13.300 | and many people won't be able to,

01:02:15.460 | develop an eye mask procedure.

01:02:19.100 | So put an eye mask on,

01:02:20.980 | make sure you block out noise, earplugs.

01:02:23.940 | You can use a sound machine if you want,

01:02:25.460 | and we can speak about sort of sound machines

01:02:28.140 | and whether or not they're good or bad on sleep.

01:02:30.500 | And then you can lie down,

01:02:33.220 | make sure that you try to take your shoes off

01:02:38.100 | and get under some kind of a blanket,

01:02:40.420 | because we're so contextually cued

01:02:43.300 | by having something wrapped around us

01:02:45.060 | called a blanket or a duvet,

01:02:46.780 | that to do it without that,

01:02:48.460 | if you are not a natural napper, can help you.

01:02:51.260 | Again, some people will say,

01:02:52.860 | I can just kick my feet up on my desk,

01:02:54.740 | sit back in my reclining chair in the office,

01:02:57.140 | and I can fall asleep, that's great.

01:02:58.420 | But if you're not a natural person,

01:02:59.780 | I'm just trying to tell you things

01:03:01.100 | that increase the probability of that.

01:03:03.820 | And then set the alarm.

01:03:05.100 | I like your idea of making sure that if you do fall asleep,

01:03:08.900 | you don't accidentally go too long

01:03:10.660 | and then just feel miserable.

01:03:12.860 | So mimic the conditions that you're trying to get

01:03:16.780 | that you would normally get at night.

01:03:19.500 | That will increase the probability.

01:03:21.500 | Mask out noise, mask out light, kick your shoes off,

01:03:25.540 | have some kind of a blanket wrapping around you.

01:03:28.100 | That's probably the best.

01:03:28.940 | And then time it based on this sort of postprandial drop.

01:03:33.820 | You will know yourself, everyone has fallen prey to it.

01:03:38.100 | You know, it's usually around about three, 4 p.m.

01:03:42.100 | that I do start to feel this decline,

01:03:44.420 | or it's around 1 p.m.

01:03:46.020 | Try to match it in accordance with that.

01:03:48.540 | So those are the first, I think, two questions.

01:03:51.060 | Should you?

01:03:51.900 | Not necessarily.

01:03:53.260 | If you would like to and are not normally doing it,

01:03:55.940 | how can you do it?

01:03:57.780 | The final point I think is fascinating,

01:03:59.820 | which is these alternate states of conscious brain activity.

01:04:04.820 | The most obvious is when we're awake and when we're asleep.

01:04:10.580 | Those are the two most dramatic changes in consciousness

01:04:14.380 | that we experience on a daily basis, short of anesthesia.

01:04:18.060 | I've become, like you, very fascinated

01:04:21.300 | by these sort of both meditative states

01:04:24.380 | or these liminal states.

01:04:26.700 | I think at some point you and I should collaborate

01:04:28.500 | and we should do some work and really unpack this.

01:04:31.420 | But the reason I find this interesting

01:04:33.060 | is because I'm going to guess

01:04:34.820 | you are having sleep-like states,

01:04:38.260 | but you are not fully asleep.

01:04:40.740 | How would I define a sleep-like state?

01:04:43.900 | What we've learned is that your brain,

01:04:46.060 | the way it sleeps, isn't en masse.

01:04:48.900 | It's not as though your entire brain sleeps.

01:04:53.140 | Different territories of your brain

01:04:56.020 | can sleep in different ways.

01:04:58.420 | And what we've also known, and there's some argument,

01:05:03.300 | even individual brain cells seem to have a period

01:05:07.020 | where they go into sleep.

01:05:08.620 | And these individual neurons will start to show

01:05:11.340 | what look like these beautiful, big, powerful,

01:05:13.980 | deep, slow waves in terms of their firing rate, at least,

01:05:17.420 | in terms of those neurons firing away.

01:05:20.500 | I bring this up because if that means

01:05:22.940 | that your brain can have local sleep

01:05:26.460 | rather than global sleep,

01:05:29.060 | if you are in global sleep, you're out like a light.

01:05:32.940 | You are asleep.

01:05:34.620 | But perhaps these liminal states,

01:05:37.060 | the reason that they give these benefits

01:05:38.940 | is because you are still awake, not global sleep.

01:05:43.140 | So if you're in global sleep, you're asleep,

01:05:44.940 | but you're awake, so you're not in global sleep,

01:05:47.340 | but you may be having local sleep.

01:05:49.700 | Now, using special setups in my laboratory,

01:05:53.380 | we can apply tens, maybe hundreds of electrodes

01:05:57.420 | all over your head, and we can map

01:06:00.540 | the different places where your brain is having sleep

01:06:05.380 | in much higher resolution.

01:06:07.660 | So rather than a 480 DPI movie on YouTube,

01:06:12.660 | I'm now in 4K resolution.

01:06:15.540 | I can really dismantle what's going on

01:06:19.060 | analytically in your brain.

01:06:20.780 | I'm going to guess that when you're going into these states

01:06:23.500 | and you report coming out of those states,

01:06:25.460 | and I ask you, on a scale of one to 10,

01:06:28.900 | how would you rate that as an experience

01:06:31.300 | based on your common experience?

01:06:33.180 | The greater the intensity of the liminal benefit

01:06:38.500 | and state that you experienced, I'm going to predict

01:06:41.740 | is directly related to the extent of this local,

01:06:45.660 | deep, non-REM, slow-wave sleep that's happening.

01:06:48.420 | You're still awake, but some parts of your brain

01:06:50.940 | for maybe seconds of time, or maybe even tens

01:06:54.180 | of seconds of time, I'm going to bet,

01:06:56.540 | will be oscillating in what look like

01:06:59.100 | slow-wave sleep, deep sleep states.

01:07:02.180 | And if all I would be able to look at

01:07:04.420 | is that one part of your brain

01:07:06.060 | and that small cluster of electrodes,

01:07:08.140 | and someone said to me, "Is this person awake or asleep?"

01:07:11.220 | I would say, "Oh, they're asleep, they're in deep sleep."

01:07:13.780 | But then if you slowly reveal and back out

01:07:16.140 | and show me the rest of the brain and what it's doing,

01:07:18.740 | I would say, "Oh my goodness,

01:07:20.580 | no, this person must be awake."

01:07:22.660 | But that local territory, that district up there

01:07:25.300 | in their brain, they were having slow-wave sleep.

01:07:28.220 | I think that's what we could find.

01:07:32.260 | And that may predict some of the benefits that you get,

01:07:35.060 | some of the productivity energy benefits.

01:07:37.260 | By the way, I should note that with all of this nap,

01:07:40.820 | racket, NASA figured this out back in the 1980s.

01:07:45.260 | They were looking at ways to optimize their astronauts

01:07:48.860 | because when you are up in orbit,

01:07:51.100 | depending on what orbit you're in,

01:07:52.820 | you are rotating around the planet

01:07:54.540 | maybe 10, 20 times per 24 hours.

01:07:57.940 | So you're seeing 10 to 20 sunsets and sunrises.

01:08:02.940 | So your sleep is a total mess.

01:08:06.060 | And you can safety check almost everything

01:08:09.300 | in terms of technology.

01:08:11.060 | But the one weak link in a space mission

01:08:13.620 | is this thing called the human being.

01:08:15.180 | That's where errors typically happen.

01:08:17.340 | So how do you de-risk a human error up in space?

01:08:21.940 | Because if you make an error up there,

01:08:24.100 | I mean, on the ground, not great,

01:08:25.460 | up there, kind of catastrophic.

01:08:28.300 | You can try to optimize the ability to sleep

01:08:32.340 | and their ability to maintain focus,

01:08:34.100 | concentration, alertness, and productivity.

01:08:36.660 | And what they found was that these naps

01:08:39.020 | produced almost a 20% boost in short naps,

01:08:43.500 | 20% boost in their alertness,

01:08:45.140 | and almost a 50% boost in their task productivity.

01:08:50.020 | And it was so powerful that it translated

01:08:52.460 | to the terrestrial employees of NASA on the ground.

01:08:57.460 | And it became what was known as the NASA nap culture.

01:09:01.140 | And from there on, we had what were called power naps.

01:09:04.860 | Power naps, by the way, why are they called power naps?

01:09:08.420 | And you think, well, just because it powers me up.

01:09:11.740 | It's a good idea, but it's wrong.

01:09:13.820 | It has a very specific story, a fascinating one.

01:09:16.540 | Two legends in my field, David Dinges and Mark Rosekind,

01:09:21.540 | they were looking at how to instigate risk mitigation,

01:09:26.660 | not in astronauts, but in pilots

01:09:29.740 | who are doing long haul flights.

01:09:32.500 | Because the most dangerous aspect of a long haul flight

01:09:36.180 | is when it is coming down to land.

01:09:38.740 | And that's when they can sometimes have these things

01:09:41.740 | called a catastrophic hull loss,

01:09:44.980 | which is a euphemistic phrase for a terrible plane crash.

01:09:49.540 | And they were trying to say,

01:09:50.460 | how could you use naps strategically to de-risk that

01:09:54.860 | and improve their alertness?

01:09:56.420 | And they asked a very interesting question.

01:09:59.140 | If they can nap for only a certain period of time,

01:10:02.380 | because they have to be at work on the plane

01:10:05.620 | for the rest of it, when should you place that nap?

01:10:08.380 | Should you do it at the start of the long haul flight,

01:10:11.540 | in the middle or towards the end?

01:10:14.420 | And most people would bet, like they I think did,

01:10:17.740 | it's best to place it at the end

01:10:19.780 | when you're really starting to struggle, get that boost.

01:10:23.220 | And then you wake up, you're not in sleep inertia

01:10:25.980 | 'cause it's been brief.

01:10:27.300 | And then you're energized for landing.

01:10:29.900 | They didn't find that.

01:10:31.220 | They found that the most optimal time to nap

01:10:34.260 | was early on in that long haul flight.

01:10:37.820 | And it sustained them throughout the rest of the flight.

01:10:41.980 | Now they took their findings to the FAA

01:10:45.020 | who are funding the work

01:10:47.060 | and the Federal Aviation Authority

01:10:49.660 | here in the United States.

01:10:51.220 | And they said, we've got some great findings

01:10:53.220 | and we think we should implement this.

01:10:55.700 | And we would like to use a term

01:10:57.660 | to help pilots understand this.

01:10:59.780 | And it's called prophylactic napping.

01:11:02.420 | And of course there were many chuckles throughout the room,

01:11:07.700 | perhaps inappropriate.

01:11:09.260 | And they just said, look, you've got to understand

01:11:12.380 | our pilots that, you know, kind of alpha male guys.

01:11:16.220 | And if you're starting to say

01:11:17.340 | you need to prophylactically nap,

01:11:19.260 | it's not gonna be adopted.

01:11:20.660 | That's a no-go.

01:11:22.180 | So they looked around the room

01:11:23.700 | because it's an alpha male culture.

01:11:25.500 | It's a mostly masculine culture at that time.

01:11:28.660 | They said, what could we,

01:11:29.780 | and there's a lot of beard stroking.

01:11:31.060 | And they said, I've got it, power naps.

01:11:33.620 | It's gotta be about power.

01:11:34.980 | And so that is where if you've ever wondered

01:11:37.660 | where the term power naps come from,

01:11:39.940 | it's not because it reboosts your power,

01:11:41.820 | which it does and boost it back up.

01:11:44.420 | It's because there was chuckles at the time,

01:11:48.140 | prophylactic napping.

01:11:50.060 | - I'd like to take a brief break

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01:11:57.780 | Many times on this podcast,

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01:12:50.620 | The naming of things fascinates me,

01:12:52.260 | especially in the landscape of health and wellbeing also.

01:12:57.260 | And that's one reason why having become a real fan

01:13:04.220 | and practitioner of Yoga Nidra,

01:13:06.020 | which I think translates to yoga sleep,

01:13:07.760 | which is this process of lying down

01:13:09.400 | for a period of 30 to 60 minutes, progressive relaxation.

01:13:13.940 | These are scripts that are readily available

01:13:15.700 | as this is an age-old practice in India.

01:13:22.240 | That is meant to restore mental and physical vigor

01:13:26.220 | by placing one into one of these liminal states.

01:13:28.900 | And I have great respect for the Nidra tradition,

01:13:32.340 | but sometimes the names are a separator.

01:13:36.520 | So people who hear Yoga Nidra and they think,

01:13:38.860 | oh, it must be yoga movement.

01:13:40.120 | And that's of course not true.

01:13:41.260 | Or they think that there must be

01:13:42.980 | some mystical component to it,

01:13:44.320 | which is not necessarily true.

01:13:46.140 | Sometimes they include intentions and things like that,

01:13:48.260 | but often not.

01:13:49.420 | So that's why I coined this phrase, non-sleep deep rest,

01:13:53.580 | which is essentially maintains the critical components

01:13:56.740 | of Yoga Nidra, but doesn't include intentions

01:14:00.100 | and has these shorter 10 or 20 minute protocols.

01:14:04.500 | So it'd be great fun.

01:14:06.100 | And I think very interesting for us to do that project,

01:14:08.700 | to explore what are the brain's activation states

01:14:11.500 | or deactivation states as the case may be

01:14:13.820 | in these non-traditional or liminal state practices.

01:14:17.820 | Now, along the lines of power napping,

01:14:20.220 | specifically in the naming of power napping,

01:14:22.020 | I think it's more than just an anecdote,

01:14:26.580 | because I think it is very important

01:14:28.340 | for people to understand that these protocols,

01:14:33.340 | these tools that NASA and that laboratories have developed,

01:14:37.660 | oftentimes are for other purposes,

01:14:40.180 | but they translate to a kind of broader significance.

01:14:42.700 | And what I'm hearing and what I'm starting to integrate

01:14:45.660 | as we have today's conversation is that it seems

01:14:48.500 | that there is pretty good reason to at least explore

01:14:53.500 | biphasic sleep, right?

01:14:55.600 | That for the non-nappers to really think about

01:14:58.980 | whether or not they would like to explore napping,

01:15:01.420 | as you mentioned, they don't have to.

01:15:02.620 | And then for people who are already napping,

01:15:05.720 | to really think about the placement of that nap

01:15:08.500 | within the day and the duration of that nap.

01:15:10.960 | What you told us a few moments ago suggests

01:15:13.540 | that I should be doing, or anyone that's doing naps

01:15:17.140 | or entering these liminal states like NSDR,

01:15:19.980 | might wanna shift them a little bit earlier

01:15:22.540 | than the period in which they first become sleepy

01:15:25.500 | to take that nap.

01:15:27.060 | Is that right?

01:15:27.940 | I mean, so for instance, should I do as my colleague

01:15:30.300 | and finish lunch and lie down for 10, 15 minutes

01:15:34.540 | rather than wait until two or 3 p.m.?

01:15:37.060 | Is that something that could make a meaningful difference?

01:15:39.580 | - I think it could.

01:15:40.660 | And I think it really, again, depends on how much

01:15:42.660 | of a struggle sleep becomes in the evening for you.

01:15:46.500 | If it is becoming the later that you nap,

01:15:49.960 | if your sleep becomes either A,

01:15:52.060 | more difficult to initiate in the evening,

01:15:54.540 | or maybe you don't have any problems falling asleep.

01:15:57.340 | But for some reason, when I look back,

01:15:59.660 | I'm now starting to wake up more throughout the night.

01:16:02.700 | That in part, again, it's not just that

01:16:05.240 | if you nap late in the day, you struggle to fall asleep.

01:16:08.260 | You may not.

01:16:09.500 | The other consequence that can happen,

01:16:11.460 | which is non-mutually exclusive,

01:16:13.500 | is that you then stay in not as deep a sleep

01:16:17.940 | and your sleep is more fragile in that sense.

01:16:21.260 | So the probability that you will wake up

01:16:24.340 | because you had the nap so late in the day

01:16:28.260 | is higher in the middle of the night.

01:16:30.540 | And then when you wake up, like many of us do,

01:16:33.300 | and you go to the restroom or it's perfectly natural,

01:16:36.880 | but the speed with which you can then fall back asleep

01:16:40.220 | is compromised, why?

01:16:41.980 | Because you've jettisoned some of that sleepiness

01:16:44.740 | by way of the nap.

01:16:46.220 | And there isn't as much to take you back down into sleep

01:16:50.180 | after you've woken up.

01:16:51.700 | So I would just say that if you are seeing that pattern,

01:16:55.260 | that the later napping that you're doing,

01:16:57.900 | if you're doing that, and again,

01:16:59.140 | there's no reason that you need to nap

01:17:00.860 | only if you choose to nap.

01:17:02.380 | If that's the case,

01:17:03.700 | then consider not necessarily obviating the nap.

01:17:07.340 | That may not be required.

01:17:09.160 | Just bring it back earlier, take it after lunch,

01:17:12.580 | see how things work out, do the experiment.

01:17:15.020 | And when you do the experiment,

01:17:16.260 | make sure that you do what I would describe

01:17:18.020 | as the on-off-on experiment,

01:17:20.380 | which is where you're napping as you normally do,

01:17:23.760 | and you've noticed perhaps some problems with your sleep.

01:17:26.660 | Then do, so that's sort of the,

01:17:29.380 | well, it's sort of the on-off-on phase.

01:17:33.200 | So then change your nap protocol and move it earlier.

01:17:37.880 | So now you've switched off your standard protocol

01:17:41.420 | and you've moved on to something different.

01:17:43.060 | So you're on your standard protocol and then you come off it

01:17:46.180 | and when you come off it, meaning you go to an earlier nap

01:17:49.420 | and you say, gosh, things do seem to be better.

01:17:52.180 | Maybe he had something there and it just seemed to improve.

01:17:55.320 | Good, but I don't trust that

01:17:58.260 | because maybe it's just a placebo effect

01:18:00.180 | that you hear some dulcet British tones

01:18:04.160 | and you get convinced that maybe that would work

01:18:06.360 | and now instead, after about two weeks of doing that

01:18:11.360 | and things have improved, go back to your original schedule,

01:18:14.860 | go back on to your original protocol.

01:18:17.860 | I'm not as interested about the fact

01:18:20.700 | that things got better when we changed it.

01:18:23.340 | I'm interested in the question,

01:18:24.980 | do things get worse when we stop it?

01:18:28.140 | And so when we stop the intervention,

01:18:30.140 | if things got worse again, now I'm believing it a lot more.

01:18:33.500 | So just as a tip, if you are a self-tinkerer

01:18:36.440 | and so you don't have to do that,

01:18:37.640 | but if you're idiotic like me and a scientist

01:18:40.000 | and you want to do it with the city rigor,

01:18:42.640 | that's the way I would suggest doing it.

01:18:44.600 | - I don't think it's idiotic at all.

01:18:45.960 | I think it's systematic.

01:18:47.080 | And what you just described is both a negative control

01:18:50.520 | and a positive control experiment.

01:18:52.120 | So you're- - Thank you.

01:18:53.240 | - You are a scientist- - To add the terms.

01:18:55.240 | - Through and through.

01:18:56.600 | Are there any individuals

01:18:58.940 | that should absolutely avoid napping?

01:19:01.080 | You know, I've heard lore of, you know,

01:19:04.580 | elderly folks, folks with certain conditions,

01:19:08.500 | you know, I can't imagine which,

01:19:12.860 | but I'm sure you'll tell us,

01:19:14.940 | that for whom napping is harmful to their health.

01:19:18.740 | - It's a very, I think, interesting question

01:19:22.060 | because the strongest evidence comes back to that,

01:19:24.460 | which we've mentioned before, which is insomnia.

01:19:27.620 | And really the recommendation there is just avoid naps.

01:19:31.920 | And what's problematic about insomnia,

01:19:35.840 | when you are having such tough times with sleep at night

01:19:40.840 | and you are just dragging through the day, it is miserable.

01:19:44.680 | And I am, you know, I am very protective of my sleep.

01:19:49.680 | For the most part, I sleep pretty well,

01:19:53.160 | but I'm not immune to the vagaries of sleep.

01:19:57.040 | I've had two bouts of insomnia throughout my life.

01:19:59.600 | Both have been what we call reactive insomnia,

01:20:01.800 | reactive to an event or something happening.

01:20:05.400 | And I know how just desperate and hungry you are for sleep.

01:20:10.400 | And if it's happening week after week, month after month,

01:20:17.280 | I'll just do anything to get sleep when I can.

01:20:20.120 | And the temptation therefore to nap

01:20:23.440 | when you are suffering from insomnia is that much higher.

01:20:26.720 | And therefore the advice is that much harder to adopt.

01:20:30.480 | But trust me, that is one of the components

01:20:33.120 | that we have in the psychological treatment bucket

01:20:37.080 | that we use for insomnia,

01:20:38.400 | which is called cognitive behavioral therapy for insomnia

01:20:41.360 | or CBTI for short.

01:20:43.880 | And you can just look it up or on my own podcast

01:20:46.680 | I did a six part series on insomnia.

01:20:49.880 | So I would say try to back away in that circumstance,

01:20:53.880 | but you brought up another example, which is in aging.

01:20:57.200 | There I think the evidence is a little less causal.

01:21:00.640 | So you have to be more cautious

01:21:02.600 | about recommending the absence

01:21:05.200 | as I was with insomnia of abstaining from naps.

01:21:09.440 | But the data has now become quite strong

01:21:11.720 | that when you get past about 65 years old

01:21:15.720 | and you look at napping behavior

01:21:18.000 | in large epidemiological studies,

01:21:20.440 | and you say, is there a positive benefit in aging for napping

01:21:25.440 | or is there no benefit at all?

01:21:28.320 | And they looked at that because they thought,

01:21:29.800 | well, that perhaps based on the work in healthy adults

01:21:33.080 | that I've described, that would be good for older adults.

01:21:36.480 | Not only did they find that it wasn't good,

01:21:38.920 | they found that it was deleterious,

01:21:40.880 | that napping in older adults was predictive

01:21:43.680 | of worse health outcomes.

01:21:46.800 | And it also seemed to predict a higher likelihood

01:21:50.360 | of early mortality.

01:21:52.160 | So at this point we're thinking,

01:21:54.200 | well, how does that fit with everything

01:21:56.560 | you've been telling us?

01:21:58.520 | It comes back to this notion of bad sleep at night.

01:22:02.080 | It's probably not necessarily that napping during the day

01:22:06.600 | is bad for older adults.

01:22:09.760 | It's that the naps reflect a problem

01:22:14.360 | with the night of sleep for older adults.

01:22:18.320 | And as we get older,

01:22:19.520 | something I didn't mention during development

01:22:22.080 | was that yes, we get this sort of stable ratio

01:22:25.200 | of four to one of one part REM sleep,

01:22:28.160 | four parts non-REM in our seven to nine hours.

01:22:31.720 | And I described these changes in REM early in development.

01:22:35.160 | I didn't mention two things

01:22:36.520 | about non-REM slow wave activity.

01:22:38.840 | First, as we go into our teenage years

01:22:41.560 | and we shift our sort of timing of sleep

01:22:44.000 | where we want to go to bed later and wake up later,

01:22:46.000 | that's biologically determined.

01:22:47.480 | It's not teenagers fault.

01:22:49.440 | Something happens with their deep sleep.

01:22:51.240 | However, their deep sleep starts to do a different

01:22:56.240 | or different action to the brain

01:22:59.640 | that REM sleep was doing as an infant.

01:23:02.640 | I said that during infancy,

01:23:04.480 | we have huge amounts of REM sleep

01:23:06.360 | and we're growing synapses, synaptogenesis,

01:23:09.560 | and we're wiring up all of those new territories,

01:23:12.160 | all of these new neighborhoods with fiber optic cable.

01:23:14.920 | But let's say that you've now run the experiment

01:23:17.240 | across many years through until teenagehood

01:23:20.000 | of those neighborhoods.

01:23:21.160 | And you've been measuring the bandwidth consumption

01:23:24.440 | of each individual house.

01:23:26.840 | And you've started to realize,

01:23:27.960 | well, I wanted to create a big spread across the brain.

01:23:31.760 | And then I'm just going to let experience

01:23:33.680 | over the next year's time,

01:23:35.440 | tell me which parts of the brain

01:23:37.760 | seem to enjoy that high bandwidth

01:23:39.920 | and which parts don't seem to use it very much.

01:23:42.640 | And as we go through into our teenage years,

01:23:45.080 | we go through something called synaptic pruning

01:23:48.080 | where the brain actually culls and takes away synapses

01:23:52.800 | from certain parts of the brain.

01:23:54.720 | It seems to be that this change in slow wave sleep

01:23:57.400 | that happens around these adolescent years

01:24:00.120 | is performing the act of final cortical maturation

01:24:04.880 | that it's downscaling the synapses

01:24:07.520 | and fine tuning the brain.

01:24:09.480 | So you've got this beautiful efficiency

01:24:11.840 | and now you've throttled back some of the bandwidth

01:24:15.040 | from some of those neighborhoods

01:24:16.920 | because they just don't use it very much.

01:24:18.880 | And you can move it over into the territories

01:24:21.840 | that are demanding more bandwidth

01:24:24.040 | and net, net, the brain is downscaled,

01:24:27.000 | but it's improved its efficiency

01:24:29.120 | in the sense that those regions that need it

01:24:31.400 | and are working hard based on what we think

01:24:33.960 | this organism has been doing over the past 13 years,

01:24:37.920 | that's where we need to now place our bets.

01:24:40.520 | But as we get through into our older years,

01:24:43.800 | and this will come back to this issue of napping,

01:24:46.600 | don't worry, stick with me here, folks.

01:24:49.640 | The reason is that as we're getting older,

01:24:53.520 | our sleep declines, but it's not just all sleep declines.

01:24:58.520 | Deep sleep declines most dramatically.

01:25:03.360 | And we all think of aging from brain perspective

01:25:06.680 | as cognitive decline that our learning

01:25:08.680 | and memory abilities begin to fade and decline.

01:25:11.280 | And they do.

01:25:12.920 | But I would argue that a physiological signature of aging

01:25:17.240 | is that your sleep gets worse

01:25:18.720 | and particularly your deep sleep.

01:25:20.800 | What's perhaps concerning for people listening

01:25:23.400 | to this right now is that that decline in deep sleep

01:25:27.280 | doesn't start happening in your 60s or your 50s

01:25:31.120 | or even your 40s.

01:25:32.800 | We can start to pick up that great sleep decline

01:25:35.320 | beginning in your mid to late 30s.

01:25:38.520 | And then it just decreases.

01:25:39.960 | And by age 50, you are down to about 50%

01:25:44.360 | of the deep non-REM sleep that you were having

01:25:46.760 | when you were 17 or 18.

01:25:49.240 | By age 65 and over, or certainly by age 75,

01:25:53.240 | you are down to about just 5% of the deep sleep

01:25:57.440 | that you had when you were 17 or 18.

01:26:00.920 | Just a stunning decline.

01:26:03.160 | What that means comes back to the first episode.

01:26:07.040 | We spoke about the four macros of good sleep,

01:26:09.760 | quantity, quality, timing, and regularity.

01:26:13.640 | One of the measures of quality that I described to you

01:26:16.320 | was this electrical quality of deep sleep.

01:26:19.160 | The other measure of quality sleep I spoke about

01:26:22.960 | was how consolidated and consistent your sleep is

01:26:25.920 | versus how fragmented your sleep is.

01:26:28.640 | The measure of sleep quality

01:26:31.200 | is markedly compromised as we get older.

01:26:33.800 | We're waking up many more times.

01:26:36.000 | Our sleep is much more fragmented

01:26:38.440 | and therefore our sleep efficiency is worse.

01:26:40.960 | And we've got this huge decline in our deep non-REM sleep.

01:26:45.640 | So no wonder then when you are awake during the day

01:26:49.200 | as an older adult,

01:26:51.360 | your sleep quality is so compromised at that stage,

01:26:55.560 | you perhaps try to compensate by way of napping.

01:26:59.400 | But that compromised quality of sleep

01:27:01.440 | that you're having at night is probably the reason

01:27:04.200 | that you start to get sick more,

01:27:06.000 | that you have a higher probability of illness and disease

01:27:10.160 | and why also you probably have a higher risk

01:27:13.040 | of premature mortality.

01:27:15.120 | So in other words, it's the bad quality of sleep at night

01:27:19.680 | that leads to this behavior

01:27:21.240 | that we call daytime napping in older adults

01:27:24.520 | that seems to indirectly suggest,

01:27:27.560 | oh my goodness, it's daytime napping that's bad

01:27:31.040 | and that causes these problems

01:27:32.760 | when in fact it's that daytime napping is a proxy

01:27:36.280 | for the bad sleep that's happening at night.

01:27:38.640 | And it's really the bad sleep that's happening at night

01:27:41.200 | that is more directly related to the health

01:27:44.120 | and mortality concerns in older adults.

01:27:46.640 | So that's why I think right now as a field,

01:27:49.400 | I'm still open to evidence that napping for some reason

01:27:52.920 | that we just do not understand right now is problematic

01:27:57.920 | and does causally predict worse health

01:28:01.480 | and a shorter lifespan in older adults.

01:28:04.240 | I think the best evidence that we have right now

01:28:06.400 | is that it's actually the bad quality of sleep at night

01:28:09.280 | and thus we should not be necessarily jumping

01:28:11.840 | to recommendations that all older adults

01:28:14.520 | should stop napping.

01:28:15.760 | I think we need more evidence

01:28:17.120 | and I'm open to both sides of that.

01:28:19.040 | - Let's talk about caffeine.

01:28:21.520 | I've heard the term, is it Nappuccino?

01:28:26.520 | - Yeah.

01:28:28.080 | - I think it refers to a practice

01:28:30.480 | of drinking some caffeine, then laying down for a nap

01:28:33.360 | and then supposedly waking up, feeling more refreshed.

01:28:37.040 | My understanding, and you'll tell us more of course,

01:28:39.120 | is that caffeine is effectively an adenosine antagonist,

01:28:44.040 | although it's a competitive agonist.

01:28:46.440 | You'll explain, I'm sure.

01:28:48.840 | And napping, as you mentioned before,

01:28:52.120 | removes some of the sleep pressure,

01:28:53.640 | AKA wipes away some of that adenosine that's accumulated.

01:28:59.520 | Both of which sound great, but as you mentioned earlier,

01:29:04.200 | there's a warning there as well.

01:29:06.120 | The warning label on both those things should be

01:29:08.880 | that having sufficient adenosine built up in your brain

01:29:13.120 | is one of the ways in which you feel sleepy at night

01:29:15.560 | and fall asleep and stay asleep.

01:29:17.840 | So what's the story with caffeine?

01:29:20.760 | How does it work to make us feel more alert?

01:29:23.600 | And what is the rationale for the napping?

01:29:28.600 | - The nappuccino.

01:29:30.080 | - The nappuccino, also known as the caffeine nap.

01:29:33.520 | Caffeine is a very interesting compound

01:29:36.840 | in relationship to sleep and wake.

01:29:39.320 | Obviously everyone knows that caffeine

01:29:41.280 | can help you stay awake.

01:29:43.680 | It's no coincidence that those two words that you've used

01:29:47.680 | about these chemical compounds,

01:29:49.080 | caffeine and adenosine sound the same.

01:29:52.840 | It's because the receptor that, or the receptor systems

01:29:57.200 | that caffeine targets in your brain

01:29:59.680 | are the adenosine receptors.

01:30:03.040 | And you think, well, Matt was telling me

01:30:05.160 | that the more adenosine that builds up,

01:30:07.880 | in other words, the more adenosine that's latching

01:30:09.840 | onto those adenosine receptors in your brain,

01:30:13.400 | the sleepier that you feel.

01:30:15.960 | And I'm telling you that caffeine works

01:30:18.280 | on those same receptors.

01:30:19.480 | That doesn't make sense.

01:30:21.160 | Caffeine, if it's working on those same receptors,

01:30:24.360 | should increase your sleepiness.

01:30:27.040 | It doesn't because when it binds

01:30:29.880 | onto those adenosine receptors,

01:30:31.760 | those welcome sites in the brain,

01:30:34.240 | it simply blocks them.

01:30:36.120 | It doesn't deactivate them, nor does it activate them.

01:30:40.200 | It simply blocks them.

01:30:42.480 | So think about it almost a little bit like a room

01:30:46.280 | that's full of chairs.

01:30:48.360 | And at some point, these adenosine,

01:30:51.240 | which is one collection of people

01:30:52.880 | with the name badges of adenosine,

01:30:54.800 | they would normally like to come in

01:30:56.160 | and start sitting down on those seats,

01:30:58.640 | which are the adenosine receptors.

01:31:00.800 | And as they sit down on those seats,

01:31:02.800 | you're building up this signal of sleepiness.

01:31:06.160 | Well, caffeine, which is another group of people

01:31:09.320 | with caffeine badges, they race into the room

01:31:12.040 | and they start to hijack the seats

01:31:14.080 | and they start to sit down on them.

01:31:15.960 | And all of a sudden, adenosine can't find any seats

01:31:19.680 | to sit on.

01:31:21.360 | So your brain is still flooding that room

01:31:25.600 | with adenosine.

01:31:27.160 | So the adenosine is still building up,

01:31:29.960 | but the reason that you don't feel sleepy anymore

01:31:33.200 | when you've had a shot of caffeine

01:31:35.920 | is because caffeine has raced in,

01:31:38.000 | it's latched onto the receptors,

01:31:40.960 | and it has essentially hit the mute button

01:31:43.480 | on your sleepiness.

01:31:44.800 | So now your brain was thinking,

01:31:47.480 | "Gosh, I've been awake for about 13 or 14 hours.

01:31:50.920 | "I'm starting to feel it.

01:31:52.000 | "I'm just gonna take a quick espresso shot."

01:31:55.280 | And you get that, you think,

01:31:56.800 | "Well, hang on a second, 20, 30 minutes later,

01:31:59.920 | "I don't feel as tired anymore."

01:32:01.960 | Why?

01:32:02.800 | It's not because caffeine came in

01:32:05.000 | and removed the adenosine, it didn't.

01:32:09.160 | Caffeine has come in, blocked the sites,

01:32:12.040 | but the adenosine is still building up.

01:32:14.120 | And then at some point, the caffeine wears off.

01:32:19.000 | And therefore, not only do you go back

01:32:21.880 | to the same level of adenosine

01:32:24.520 | that you did two hours ago,

01:32:27.040 | it's that plus the additional two hours of adenosine

01:32:30.560 | that has been building up.

01:32:32.200 | And what you experience is something called a caffeine crash.

01:32:35.520 | And now you need even more caffeine,

01:32:37.960 | not just to get you back to where you were,

01:32:40.160 | but to recover the crash that you've had and go further.

01:32:43.040 | Caffeine in relationship to the caffeine nap,

01:32:47.400 | though the nappuccino is relevant because of its timing.

01:32:51.640 | Caffeine has an instigating action

01:32:56.360 | of around 12, 14 to 17 minutes.

01:33:01.360 | So when you come through in the morning

01:33:03.560 | and you grab your first cup of coffee,

01:33:06.440 | and within the first four or five minutes,

01:33:10.520 | you say, "I just feel better.

01:33:12.680 | "I've just had a couple of sips.

01:33:13.920 | "I've had half a cup of coffee and I already feel better.

01:33:17.120 | "I just needed that."

01:33:18.760 | If it's within the first five minutes

01:33:20.560 | that you're experiencing that,

01:33:21.920 | it's got nothing to do with the caffeine

01:33:25.000 | because the peak plasma concentration of your caffeine

01:33:27.840 | is not going to arrive with you

01:33:29.760 | until about 12 to 17 minutes.

01:33:33.160 | So why do you feel better?

01:33:34.640 | Some of it is placebo 'cause you're smelling the coffee

01:33:37.160 | and you associate it with alertness.

01:33:38.880 | It's really not that though.

01:33:40.360 | - Or when you say placebo,

01:33:42.120 | I also wonder whether or not

01:33:43.160 | it's possibly a conditioned effect,

01:33:46.480 | like a Pavlovian thing,

01:33:47.760 | because the smell of the coffee, the taste of the coffee,

01:33:50.680 | the hum of the machine, the walking into the cafe

01:33:54.160 | and ordering it from the barista

01:33:57.000 | also creates an anticipatory arousal.

01:33:59.480 | Like the alertness is coming.

01:34:01.720 | And in that anticipation,

01:34:03.200 | there's its own form of alertness.

01:34:05.200 | - I think that's certainly a big component of it.

01:34:08.440 | The other component, however, if you look at the data

01:34:11.040 | is that it's got nothing to do with the caffeine

01:34:12.880 | in that moment.

01:34:13.720 | It's the temperature

01:34:14.680 | that most people take their caffeine warm,

01:34:17.800 | either it's tea or it's coffee,

01:34:19.840 | or it's perhaps something else

01:34:21.880 | that Andrew Huberman would drink.

01:34:23.320 | But many people--

01:34:24.160 | - Yerba mate.

01:34:25.680 | Since I was five years old,

01:34:27.080 | I don't know if I should have been drinking

01:34:29.680 | caffeinated yerba mate so young,

01:34:31.640 | maybe even four years old.

01:34:32.720 | There's a photo of me on my grandfather's lap

01:34:34.280 | drinking out of the mate gourd.

01:34:35.640 | Half my family's Argentine.

01:34:37.160 | And so I was caffeinated from a young age.

01:34:39.320 | This brain developed in a caffeinated milieu.

01:34:41.880 | - This explains so much about what I've known of you

01:34:45.960 | over these years.

01:34:46.800 | No, I'm kidding you.

01:34:47.640 | But we need to speak later, no.

01:34:50.760 | So what's interesting about that is it's the temperature.

01:34:55.760 | And I told you in the first episode

01:34:59.000 | that we need to cool down to stay asleep,

01:35:03.680 | but we need to initially warm up to fall asleep

01:35:06.480 | because warming up at that moment I was telling you

01:35:09.840 | is warming up at the periphery.

01:35:12.160 | - Warm up to cool down to fall asleep.

01:35:14.240 | - So you need to warm up to cool down to fall asleep.

01:35:16.840 | Then you need to stay cool to stay asleep.

01:35:19.400 | And then you need to warm up to wake up.

01:35:22.400 | The warming up to cool down to fall asleep

01:35:24.840 | is not warming up in the middle deeps core of your body.

01:35:29.200 | It's about warming up the hands and the feet

01:35:31.560 | and the head to dissipate the heat.

01:35:34.000 | Hence warm up the outer surfaces

01:35:37.200 | to cool down the inner core to fall asleep.

01:35:40.360 | But then I told you, you have to warm up to wake up.

01:35:44.160 | And when we take a hot drink in the morning,

01:35:48.160 | usually caffeinated,

01:35:50.040 | the change in your core body temperature

01:35:52.640 | can happen within a handful of minutes.

01:35:56.280 | So the initial benefit that you get

01:35:58.480 | from the hot cup of coffee in the morning or hot tea

01:36:02.160 | is from the temperature rise.

01:36:03.840 | And then you get this beautiful second kick

01:36:07.320 | from the caffeine itself.

01:36:09.320 | And that caffeine can then sustain

01:36:11.560 | for a longer period of time.

01:36:13.000 | So we mentioned this problem with napping

01:36:19.320 | that even at 25 or 30 minutes of a nap,

01:36:22.880 | you wake up with that kind of grogginess,

01:36:26.360 | that sleep inertia.

01:36:28.320 | And what, however, if I could give you the benefits

01:36:32.800 | of a nap and have you come out of the nap

01:36:35.200 | with zero sleep inertia.

01:36:39.200 | And that's what some folks started to cleverly think about.

01:36:43.240 | What if I could look at the timing of the optimal nap,

01:36:47.960 | maybe 20 minutes,

01:36:49.160 | and think about the timing

01:36:50.440 | of when peak plasma concentration of caffeine emerges.

01:36:53.360 | And I told you, it really starts to kick into gear

01:36:55.560 | around 17 minutes and it's in full swing by 20.

01:36:59.280 | What if I was creative?

01:37:02.320 | I'm going to withhold from saying idiotic enough,

01:37:05.000 | but creative enough to get into bed

01:37:09.040 | just before I turn the light out for my nap

01:37:11.840 | in the afternoon.

01:37:13.240 | I swig a quick espresso, light goes off.

01:37:17.320 | I close my eyes, I mask earplugs,

01:37:21.400 | and I'm going to drift off fine

01:37:22.600 | because the caffeine is not gonna kick in

01:37:25.560 | for another 17, 20 minutes, perhaps it's full threshold.

01:37:30.120 | So now you fall into sleep

01:37:32.960 | and you're going down into sleep.

01:37:34.720 | And if you perhaps don't make it too large

01:37:37.320 | in terms of its serving,

01:37:38.360 | the temperature change is not going to affect you

01:37:40.440 | in a negative way.

01:37:41.480 | And then just as your alarm clock

01:37:44.600 | is about to go off after 20 minutes,

01:37:47.320 | you're on the beautiful ascending swing

01:37:49.600 | of upward plasma concentration of caffeine

01:37:53.040 | and you get ejected out the other side

01:37:55.840 | with both the benefits of the nap

01:37:58.520 | together with the benefits of the caffeine.

01:38:01.120 | So you get your cake and you can eat it too.

01:38:04.200 | You get the nap absent the sleep inertia.

01:38:07.760 | And hence this created what we call the caffeine nap.

01:38:11.520 | - I love it.

01:38:13.320 | - The nappuccino.

01:38:14.160 | - The nappuccino.

01:38:16.160 | Maybe I'll give it a try.

01:38:17.760 | This is the first time I've ever heard the rationale

01:38:20.680 | and the fine structure of the nappuccino,

01:38:23.280 | but it makes sense at a logical and mechanistic level.

01:38:28.200 | - I have to ask,

01:38:29.040 | is there anything besides caffeine and sleep

01:38:32.720 | that can clear adenosine?

01:38:34.320 | Can exercise clear adenosine?

01:38:37.160 | Can a cold shower clear adenosine?

01:38:39.760 | I mean, and I understand

01:38:40.800 | that there are a bunch of competing mechanisms in the body,

01:38:42.920 | like presumably a spike in norepinephrine or adrenaline

01:38:46.200 | or both is going to impact the adenosine system.

01:38:49.040 | I once heard a great quote from a former

01:38:52.280 | member of the National Academy of Sciences,

01:38:56.360 | a brilliant guy.

01:38:57.320 | He said, you know,

01:38:58.640 | a drug is a substance that when injected into an animal

01:39:02.320 | or a human produces a scientific publication,

01:39:05.280 | meaning it is rare to find a paper

01:39:10.240 | that doesn't see some effect of some drug,

01:39:12.560 | especially on sleep, I'm told.

01:39:15.400 | As I recall, if you put aspirin REM sleep into PubMed,

01:39:18.840 | you're going to see some effect on REM sleep

01:39:20.280 | from people who take aspirin.

01:39:21.360 | Pretty much any substance that one takes

01:39:23.000 | is going to alter some feature of sleep

01:39:26.800 | or of wakeful states.

01:39:28.040 | If one is looking with a fine enough instrument,

01:39:31.320 | or is that an overstatement?

01:39:32.400 | - No, I don't think it is an overstatement.

01:39:34.120 | And it comes back to the first episode

01:39:36.560 | where we described the complexity,

01:39:38.280 | this incredible, beautiful physiological ballet.

01:39:41.640 | Certainly one of the recommendations

01:39:43.080 | when people say I get this afternoon,

01:39:45.040 | this postprandial drop in my alertness, what can I do?

01:39:47.640 | I can say you could nap.

01:39:49.120 | But another way is just get outside and walk around,

01:39:52.440 | be physically active.

01:39:54.160 | Some of that has to do with the fact

01:39:55.560 | that you'll probably get some daylight

01:39:56.840 | and daylight can be a stimulator of alertness

01:39:59.880 | as long you've told us and educated us on.

01:40:03.640 | We also know that physical activity by itself

01:40:06.560 | can increase the amount of endorphins and dynorphins

01:40:10.240 | and those are wake promoting.

01:40:12.920 | But none of those are really necessarily

01:40:15.280 | going to be altering adenosine.

01:40:18.120 | They're simply overriding the adenosine

01:40:20.560 | that is still building up.

01:40:22.040 | It really does seem to be for the most part,

01:40:24.200 | at least as all that I know,

01:40:26.560 | it's only sleep and particularly non-REM sleep

01:40:30.280 | that has the capacity to or give the brain the chance

01:40:34.160 | to remove that adenosine.

01:40:35.720 | Now, what could be interesting, I think,

01:40:37.720 | is two circumstances.

01:40:40.280 | One is where your brain becomes less metabolically active

01:40:44.360 | for another reason.

01:40:45.760 | And I told you that it's not as though

01:40:48.600 | during deep non-REM sleep

01:40:50.200 | that there is some special pulsing cleansing mechanism

01:40:54.240 | for adenosine.

01:40:55.760 | There is a cleansing system called the glymphatic system,

01:40:59.400 | which removes the toxic metabolic byproducts

01:41:02.040 | of the waking day.

01:41:03.200 | Wakefulness in some ways is biochemically

01:41:05.840 | low level brain damage

01:41:07.160 | and sleep is sanitary salvation in that regard.

01:41:10.480 | - I knew it, I knew it.

01:41:11.720 | - But which is, again, it's hubristic

01:41:13.680 | and it's going too far, but it makes a point.

01:41:17.240 | The idea here, however, is that it's not

01:41:19.480 | that there is a special system

01:41:20.880 | that is removing the adenosine during deep non-REM sleep.

01:41:24.400 | It's just that your brain is less metabolically active

01:41:27.400 | and therefore it's not producing as much adenosine.

01:41:29.760 | So the natural mechanisms that are always occurring

01:41:32.400 | in the background to be clearing adenosine

01:41:34.920 | and degrading it, simply get the chance to do that

01:41:39.120 | just as effectively as they have,

01:41:41.040 | but you're no longer working against the opposite tide

01:41:45.320 | that is growing the adenosine.

01:41:47.360 | Now, the adenosine increase has dissipated

01:41:52.320 | because you're no longer metabolically active

01:41:54.560 | during deep sleep and you get the chance to cleanse it.

01:41:56.840 | All of which is to say, therefore, that,

01:41:59.360 | and I think that would mimic that,

01:42:01.280 | such as, for example, anesthesia.

01:42:03.880 | My guess is that you probably do jettison

01:42:06.360 | some sleep pressure when you are in anesthesia.

01:42:09.880 | I also think that these liminal states,

01:42:14.160 | non-sleep deep rest could be a fascinating territory there.

01:42:19.040 | Because at that point, I'm going to guess,

01:42:21.200 | and we'll be able to see with the EEG,

01:42:23.840 | and we may also be able to do some imaging,

01:42:26.040 | depending on how you and I designed the study,

01:42:29.360 | to look at what changes in the brain

01:42:31.120 | in terms of its activation state.

01:42:33.800 | My guess is that if it does put you into something

01:42:36.520 | like slow wave activity patterns,

01:42:39.080 | that means that those territories of the brain

01:42:41.440 | are metabolically less active.

01:42:43.720 | And that allows the brain to dissipate the adenosine.

01:42:47.280 | So to your point, I don't think things

01:42:49.120 | like necessarily exercise or light change adenosine levels.

01:42:53.520 | They do give a nice alertness benefit for the reasons.

01:42:56.720 | But is there an alternative way of dissipating adenosine?

01:43:00.920 | Yes, I think anything that mimics a non

01:43:03.520 | or a less metabolically active brain

01:43:06.320 | could produce these beautiful adenosine benefits.

01:43:10.000 | - Thank you for that.

01:43:11.240 | This brings me to a question

01:43:12.920 | about the period immediately after waking

01:43:16.640 | from the nightly bout of sleep.

01:43:20.160 | I've been touting the benefits

01:43:23.280 | of delaying one's caffeine intake

01:43:25.000 | by 90 to 120 minutes after waking.

01:43:27.640 | There's a little bit of a misconception out there.

01:43:29.440 | I think people ran with the ball,

01:43:32.320 | assuming that I was mandating this

01:43:35.120 | or suggesting that everyone should do this.

01:43:37.480 | And that's simply not the case.

01:43:39.000 | I actually wake up and I'll hydrate

01:43:40.680 | and drink caffeine very close to waking

01:43:42.840 | if I'm going to exercise soon after, which I often do.

01:43:47.840 | But I've experienced, and I know others have experienced

01:43:51.160 | if they are not going to exercise immediately

01:43:53.960 | or they don't need caffeine to exercise for whatever reason,

01:43:57.160 | I've heard these people exist, I'm no such mutant,

01:44:00.920 | that delaying their caffeine intake by 90 to 120 minutes

01:44:03.680 | in some cases can offset the afternoon crash.

01:44:07.340 | Now, I want to be clear, some of that

01:44:09.560 | may be offsetting the afternoon consumption of more caffeine

01:44:13.260 | because by delaying your caffeine intake in the morning,

01:44:15.360 | then perhaps there's less of an incentive

01:44:17.320 | or requirement to drink caffeine in the afternoon.

01:44:19.180 | And all of which dominoes to,

01:44:21.640 | as we'll talk about more in this series,

01:44:24.280 | to better sleep at night

01:44:25.440 | because you're not ingesting caffeine close to bedtime.

01:44:28.060 | But at risk of taking a massive tangent,

01:44:30.480 | here's what I'd like to know

01:44:31.760 | based on what you just told us.

01:44:34.860 | If indeed sleep and lower metabolic activity

01:44:39.860 | in certain brain regions

01:44:43.900 | can help reduce adenosine levels in the brain,

01:44:47.340 | one could imagine that upon waking,

01:44:50.960 | it is either a step function from, okay,

01:44:54.640 | let's say at 5.45 AM, somebody is asleep

01:44:58.520 | and adenosine is still being cleared away

01:45:00.200 | because they're asleep.

01:45:01.200 | And then they wake up, boom,

01:45:02.700 | does adenosine clearance immediately stop?

01:45:04.940 | Well, for people who have that crumpled face grogginess

01:45:09.740 | and they wake up at 5.45, maybe even by way of alarm,

01:45:12.900 | although we don't suggest that, right?

01:45:15.060 | And they stagger into the kitchen

01:45:17.980 | and ordinarily they'd make their cup of coffee,

01:45:20.900 | but they're in a pseudo sleep state.

01:45:23.300 | So it stands to reason

01:45:24.540 | that they're still clearing adenosine.

01:45:26.060 | Now, if they are to drink caffeine right away,

01:45:28.720 | then they're, as you pointed out,

01:45:30.500 | going to block those adenosine receptors

01:45:32.160 | and there's going to be a continued buildup of adenosine

01:45:34.300 | as opposed to a clearance of adenosine.

01:45:36.500 | So this was part, not the entire reason,

01:45:39.360 | but part of the rationale for suggesting

01:45:41.060 | that people at least explore delaying caffeine slightly.

01:45:44.300 | And then there are things like the cortisol rise

01:45:46.060 | and et cetera.

01:45:47.100 | But does that kind of framework at least make logical sense?

01:45:51.180 | That doesn't mean it would hold up

01:45:52.380 | in a randomized controlled trial,

01:45:53.600 | but given that we're talking about

01:45:54.820 | essentially zero risk protocols here,

01:45:57.620 | what are your thoughts on that?

01:45:59.220 | - I think it is good advice for people to test.

01:46:02.320 | And it's good advice for two reasons.

01:46:04.120 | The first is that which you describe

01:46:06.520 | in some ways by taking caffeine on early

01:46:09.880 | and masking that adenosine.

01:46:13.440 | Also caffeine can make your brain more metabolically active,

01:46:16.760 | which means that you're going to build up

01:46:18.080 | more adenosine during the day,

01:46:19.320 | which means that sleepiness is going to arrive earlier,

01:46:21.760 | which means that perhaps that postprandial drop

01:46:24.280 | is going to be harsher

01:46:26.680 | and you're going to perhaps then need to self-medicate

01:46:29.380 | with more caffeine and so goes the vicious cycle.

01:46:32.140 | So I think that's one thing to keep in mind.

01:46:34.260 | I think that's one hypothesis.

01:46:35.680 | I think the second hypothesis for me

01:46:37.540 | or the second reason I would advocate for that

01:46:39.740 | is if you've been using caffeine that way

01:46:42.380 | for a long period of time,

01:46:44.060 | you may also be masking the quality of your sleep

01:46:49.060 | because you wake up,

01:46:51.340 | you immediately medicate with caffeine

01:46:54.340 | and you are alert, you're awake,

01:46:57.020 | and you think, well, looking back on my night,

01:47:00.500 | I'm awake now after my caffeine.

01:47:02.980 | And now is the important part of that sentence.

01:47:04.980 | I'm awake now.

01:47:06.300 | So there's nothing wrong with my sleep.

01:47:09.140 | Is that true?

01:47:10.060 | Maybe it is, maybe it's not.

01:47:11.980 | Maybe if you abstain from caffeine through

01:47:14.580 | and you have to get through the detox period,

01:47:17.140 | it's not going to, this is not the right test immediately,

01:47:20.020 | but do it for about two weeks.

01:47:22.420 | And then at that point,

01:47:23.340 | once you're free from the detox and the withdrawal,

01:47:26.060 | now you're in a somewhat naive state

01:47:28.540 | where you're taking your caffeine on,

01:47:29.860 | I'm not telling you to stop caffeine,

01:47:31.540 | you're taking it on at 11 o'clock

01:47:33.660 | after you've woken up at let's say seven o'clock

01:47:35.460 | in the morning.

01:47:36.540 | At that point, we've now got this nice clear window

01:47:39.660 | that has been consistently happening

01:47:41.180 | between seven to 11 in the morning.

01:47:44.460 | And I'm going to ask you now,

01:47:46.020 | do you feel rested, restored, and refreshed?

01:47:48.980 | And can you operate with cognitive acumen and skill

01:47:53.980 | in those first morning hours?

01:47:56.940 | Now, don't forget, we've got to get past

01:47:59.100 | the natural sleep inertia period in the first 90 minutes.

01:48:01.900 | But after the first 90 minutes of waking up

01:48:03.940 | absent of caffeine, let's say by 9 a.m. in the morning,

01:48:08.180 | are you functioning well?

01:48:10.220 | Because if you're not, and you still think,

01:48:12.660 | you know what, I don't feel restored by my sleep,

01:48:15.060 | I feel unrefreshed.

01:48:16.980 | I want to then start asking you,

01:48:18.820 | let's take a look at your sleep

01:48:20.300 | and let's see how we can get you to a more refreshed state.

01:48:23.540 | And by using caffeine first thing in the morning,

01:48:26.380 | you don't give yourself the chance to test

01:48:28.980 | whether or not subjectively you sense

01:48:32.100 | your sleep is good quality.

01:48:33.700 | Now, you don't need to do this forever,

01:48:35.980 | you can just do a test for a month

01:48:38.420 | and be asking that question.

01:48:40.100 | And if all is clear, after you've got through withdrawal

01:48:43.100 | and you've got past the first 90 minutes after waking up,

01:48:45.620 | and you tell me, now in this more caffeine naive state

01:48:48.820 | in the first few hours, I feel rest, I feel refreshed,

01:48:52.020 | I feel restored by my sleep, then that's great.

01:48:54.620 | We don't need to be concerned about your sleep.

01:48:57.660 | So that's the second reason I like it

01:48:59.580 | because it gives you the opportunity

01:49:01.700 | to test out whether or not your sleep

01:49:04.100 | is of good quality or not.

01:49:05.660 | I should also note, by the way,

01:49:07.780 | that I mentioned I've changed my mind on caffeine

01:49:11.900 | and its use, and this comes back to,

01:49:14.340 | I just raise it because you had said,

01:49:16.780 | I made this suggestion and it wasn't binary,

01:49:20.940 | it wasn't dictatorial, you don't have to do it.

01:49:23.020 | I wasn't saying that everyone needs to do it.

01:49:24.780 | And in fact, even I will tweak my schedule

01:49:28.140 | if I'm doing one thing in the morning,

01:49:29.700 | I will take on board caffeine fairly soon.

01:49:31.580 | If I'm not, I will hold off.

01:49:33.660 | I came out the gate when I first published a book

01:49:39.700 | and I was very dictatorial about it.

01:49:44.700 | And I was very monoist, I was very binary.

01:49:49.260 | It was sleep is absolute

01:49:51.580 | and it has to be this way and no other way.

01:49:56.260 | I was not in favor of caffeine

01:49:59.020 | and I was telling people about the dangers

01:50:00.580 | and there are dangers to your sleep

01:50:02.300 | and we can speak about those,

01:50:04.740 | but it was a little bit too heavy handed.

01:50:07.820 | I've changed my mind for at least two reasons.

01:50:10.300 | First, that's not the way society works or people live.

01:50:15.300 | So there's no amount just like technology

01:50:17.580 | and saying leave your phone outside of the room

01:50:20.860 | for two hours before bed

01:50:22.180 | and don't check it for the first four hours.

01:50:24.340 | That genie is out of the bottle.

01:50:26.140 | So the reason I have changed my mind on caffeine

01:50:29.020 | is because if you look at the data on caffeine,

01:50:34.020 | it's stunning for health.

01:50:37.460 | On almost every metric that we can measure,

01:50:41.100 | drinking some degree of caffeine is beneficial.

01:50:44.980 | Now, there is a U-shaped function to this,

01:50:48.580 | which is once you get past sort of three or four cups

01:50:50.940 | of coffee, then you start to go in the downward direction

01:50:54.260 | and things aren't so great.

01:50:56.500 | The contradiction, however, was that I was telling people

01:51:01.500 | caffeine, not good for your sleep

01:51:03.340 | and sleep, by the way, is wonderful for health.

01:51:06.460 | It transacts all of these benefits that we have

01:51:08.700 | and we'll discuss in this series.

01:51:11.580 | But then you compare that relative to caffeine

01:51:15.380 | and caffeine transacts many of the same health benefits.

01:51:19.940 | So how can you explain that, Mr. Sleep Scientist?

01:51:24.380 | Well, if you look, the data is very clear.

01:51:28.380 | It's not the caffeine that's the benefit.

01:51:30.860 | Most people take on board caffeine

01:51:33.020 | by way of a cup of coffee.

01:51:35.820 | And the coffee bean is packed full, not just of caffeine,

01:51:40.820 | it contains a whopping dose of antioxidants.

01:51:45.340 | And because of our deficient Western diets,

01:51:49.220 | we're so absent of these antioxidants

01:51:54.020 | that the humble cup of coffee has been asked

01:51:58.500 | to carry the Herculean weight

01:52:01.220 | of our antioxidant needs on its shoulders.

01:52:04.580 | So no wonder it by itself carries

01:52:07.260 | such a strong health signal

01:52:09.220 | because it's providing you with this wonderful dose

01:52:12.580 | of antioxidants in addition to caffeine.

01:52:16.060 | Case in point, if you look at decaffeinated coffee,

01:52:19.580 | you still get the antioxidants,

01:52:22.100 | but now you don't get the caffeine

01:52:23.980 | and lo and behold, you get many of the same health benefits.

01:52:27.340 | It's not the caffeine, it's the coffee itself.

01:52:30.140 | So I think that is a perfectly good reason

01:52:35.140 | to justify caffeine, but again, just like naps,

01:52:38.180 | the dose and the timing make the poison.

01:52:40.860 | If you're not someone who's sensitive to caffeine,

01:52:43.300 | then having a couple of cups of caffeine

01:52:46.060 | and trying to step away from the use of caffeine,

01:52:49.060 | I would argue somewhere between 10 to 12 hours

01:52:52.420 | before you expect to go to bed,

01:52:54.300 | depending on your sensitivity.

01:52:56.180 | And it is different across people

01:52:57.940 | and we know that it's genetic.

01:52:59.860 | There is a specific, what we call polymorphism,

01:53:03.540 | which just means a variation in a particular gene.

01:53:06.900 | And if you look at variations in that,

01:53:09.620 | it will predict whether you are someone

01:53:11.220 | who is very sensitive to caffeine

01:53:13.340 | or not very sensitive to caffeine.

01:53:16.300 | And it comes down to how quickly you can essentially

01:53:19.420 | metabolically remove that caffeine from the system.

01:53:23.460 | So if you know that you're a very sensitive person,

01:53:25.540 | I would probably argue,

01:53:27.060 | try to steer clear maybe 12 to 14 hours.

01:53:30.460 | If you're someone who is not as sensitive,

01:53:33.580 | then you could maybe go to eight hours.

01:53:35.660 | The danger is for people who say,

01:53:38.180 | look, I'm one of those people who is,

01:53:40.740 | really just not sensitive to caffeine at all.

01:53:44.060 | And I can have an espresso with dinner

01:53:47.020 | and I fall asleep fine, I stay asleep fine.

01:53:50.140 | So it's really not a problem for me.

01:53:51.860 | I would say that that may be true,

01:53:54.700 | but the inherent danger here is that

01:53:56.420 | and we've done these studies.

01:53:57.580 | If I give you a dose of let's say 200, 300,

01:54:00.340 | 400 milligrams of caffeine in the hours before bed,

01:54:03.700 | which would be a large, strong cup of coffee

01:54:07.300 | or two espressos with dinner.

01:54:09.700 | Some people can fall asleep and some people stay asleep,

01:54:13.340 | but the amount of deep sleep that they have is compromised.

01:54:17.340 | In fact, it can drop your deep sleep by up to 20%.

01:54:20.980 | Now the danger is that you wake up in the morning

01:54:24.220 | and there was no signals in your sleep

01:54:26.980 | that said you had problematic sleep

01:54:28.460 | because you're not aware of how much deep sleep that you had.

01:54:31.860 | That's the reason that I think sleep trackers

01:54:33.900 | can be helpful in some ways.

01:54:36.380 | But you then wake up and you don't feel as refreshed

01:54:41.140 | and restored, but you don't remember having a hard time

01:54:43.540 | falling asleep or staying asleep.

01:54:44.980 | But now you find yourself reaching for three cups of coffee

01:54:47.700 | to wake up in the morning rather than the standard two.

01:54:50.220 | And so goes the vicious cycle.

01:54:52.980 | So, and also you see an interesting interrelationship.

01:54:56.300 | We did a recent study we just published

01:54:58.060 | in Wall Street Traders.

01:55:00.300 | It's not just caffeine use,

01:55:01.540 | it's also about alcohol use in the evening.

01:55:04.180 | That people who over-medicate with caffeine during the day,

01:55:08.100 | they then need something to bring them down at night.

01:55:11.700 | And the principal depressant agent,

01:55:14.980 | and depressant not in the sense of psychiatric depression,

01:55:18.740 | but in the sense of brain neural activity depression,

01:55:22.220 | is alcohol.

01:55:23.500 | So you get this classic cycle of uppers and downers.

01:55:26.940 | I need my uppers during the morning, my caffeine,

01:55:29.500 | and I need my downers at night to lull me into sleep.

01:55:33.700 | And it's this really interesting trade-off

01:55:36.260 | which we saw in these Wall Street Traders.

01:55:39.740 | So coming back to the notion of caffeine though,

01:55:42.860 | I am favorable of it in terms of its health benefits.

01:55:47.220 | I think it's very, very clear.

01:55:49.180 | Just be mindful of the dose

01:55:51.020 | and be mindful of the timing.

01:55:53.140 | Dose, try to not exceed about three cups of coffee.

01:55:56.940 | Timing, understand your sensitivity.

01:55:59.100 | There are certain genetic tests

01:56:00.260 | if you really want to get nerdy

01:56:01.500 | that will tell you if you have this sensitivity or not,

01:56:04.700 | but you will probably know it.

01:56:06.540 | And therefore just say, okay, I'm not that sensitive.

01:56:09.100 | I could probably go eight hours

01:56:10.900 | or as close as eight hours before sleep or 10 hours.

01:56:14.100 | If you're very sensitive, 14, 15 hours

01:56:17.100 | and keep it to one cup.

01:56:19.180 | So those are the ways that I would see moderating caffeine

01:56:23.340 | and changing my mind on caffeine,

01:56:26.020 | which just comes back to your point where you were saying,

01:56:28.460 | look, I made this recommendation about caffeine.

01:56:31.100 | I want to make sure I modify that

01:56:33.260 | so people don't get confused.

01:56:35.060 | I certainly needed to make a modification

01:56:38.860 | to my stance on caffeine.

01:56:40.260 | So thank you for letting me say that,

01:56:41.540 | which is a long-winded way of getting around it.

01:56:44.740 | But does that help a little bit?

01:56:46.420 | - That does help very much.

01:56:48.580 | Thank you for that addendum to the legislature.

01:56:52.020 | Okay, so you told us about the power nap

01:56:57.500 | and you've told us about the caffeine nap,

01:57:00.460 | the so-called Nappuccino.

01:57:02.580 | - Yeah.

01:57:03.420 | - What are some other types of naps

01:57:04.780 | that can be beneficial for sleep-wake cycles and alertness?

01:57:08.420 | - So you can think about the caffeine nap

01:57:12.300 | as trying to amplify it as sort of a nap plus as it were,

01:57:17.660 | but to your question, the study that comes to mind,

01:57:21.580 | there was a brilliant investigation,

01:57:24.100 | Herculean in its study design

01:57:27.180 | from a great sleep research group out in Japan.

01:57:30.420 | And they asked, okay, the nap is good.

01:57:33.940 | The caffeine nap may be a little bit better,

01:57:36.780 | but can we go further?

01:57:38.460 | And so they designed a series of studies.

01:57:43.460 | They had five different experimental groups

01:57:46.340 | and they tried to basically create a stack,

01:57:48.700 | a stacking system.

01:57:50.420 | They had across the five groups,

01:57:52.540 | there was a no-nap group, that's the control.

01:57:55.180 | Then there was a nap group.

01:57:56.700 | Then there was a nap plus caffeine group.

01:57:59.700 | Then there was a nap plus cold face

01:58:03.220 | and cold hand-washing immediately after you wake up.

01:58:07.820 | And I'll come back to explain why that we think that works.

01:58:11.060 | And then the final group was a group

01:58:12.820 | that was a nap plus bright light.

01:58:16.580 | And again, thank you, me offering this as the general public

01:58:20.860 | to you, Andrew Huberman, for your light revolution.

01:58:23.820 | So it was bright light at 2000 lux immediately afterwards.

01:58:28.820 | So they had five groups.

01:58:30.380 | Again, there was no-nap group, nap group, nap plus caffeine,

01:58:34.100 | nap plus cold hands and face-washing,

01:58:36.380 | nap plus immediate bright light.

01:58:38.940 | The cold hands and face-washing is interesting.

01:58:41.540 | I told you before that there was this three-part story

01:58:44.780 | to the sleep-wake equation,

01:58:47.180 | that you need to warm up to cool down to fall asleep,

01:58:49.420 | stay cool to stay asleep, warm up to wake up.

01:58:52.260 | And I'm saying warm up to wake up,

01:58:54.020 | but use cold water on your face and your hands.

01:58:58.140 | Don't forget that warming up, when I say it in the morning,

01:59:02.260 | is warming up at the central core of your body.

01:59:05.500 | You reverse engineer what you did in the evening.

01:59:08.420 | I said, warm up to cool down to fall asleep.

01:59:11.380 | So you warm up the periphery

01:59:13.460 | to release the blood from the core and you cool down.

01:59:16.500 | Well, the reason that they use cold hand and face-washing

01:59:19.820 | was because that's this vascular surface.

01:59:23.220 | It's the place where we can modulate temperature

01:59:25.580 | quite quickly.

01:59:26.900 | The cold water on the face and the hands

01:59:29.820 | therefore caused a vasoconstriction.

01:59:33.260 | The vessels and the capillaries there,

01:59:36.180 | they all scrunched up and they forced the blood

01:59:39.020 | back down into the core of the body.

01:59:41.580 | So the core body temperature increased a little bit.

01:59:43.940 | Now you also get a bit of an adrenaline shot

01:59:46.820 | when you're splashing very cold water

01:59:48.900 | on your hands and your face.

01:59:49.740 | So there's some of that too, but that's the justification.

01:59:52.900 | So what they find, firstly,

01:59:55.180 | they were measuring different aspects of your cognition

01:59:58.780 | and your mood and your sleepiness.

02:00:00.380 | Those were the outcome measures to assess

02:00:02.820 | how did these five different experimental groups change?

02:00:05.660 | And you can imagine, I mean, this is,

02:00:07.420 | I don't think I would ever take on a study

02:00:09.900 | where I'm doing five nap groups all within one study.

02:00:13.820 | It's bloody amazing.

02:00:15.420 | So they did the no-nap group

02:00:18.140 | and then compared to the no-nap group,

02:00:19.900 | the nap group got a wonderful benefit

02:00:22.140 | just as we described.

02:00:23.980 | And they showed benefits in their alertness,

02:00:26.860 | in their cognitive performance,

02:00:28.540 | and also they showed a reduction in their sleepiness.

02:00:32.060 | So point number one on the scoreboard for a nap.

02:00:36.500 | Then they did the nap plus the caffeine.

02:00:38.900 | And sure enough, you got an added benefit

02:00:42.860 | to that which you already obtained from the nap.

02:00:46.140 | Now it was nowhere near as sizable

02:00:48.540 | as the benefit from the nap.

02:00:49.780 | So the addition of caffeine does give you some nice benefits

02:00:53.660 | and I've used this before

02:00:54.620 | when I've worked with sort of professional athletes,

02:00:56.740 | we do instigate these nap, these caffeine naps when needed.

02:01:01.740 | So it did give a nice benefit.

02:01:04.220 | But then when they looked at the nap

02:01:06.660 | plus cold hand and face washing

02:01:09.140 | and the nap plus the bright light,

02:01:11.820 | those also added something to the nap benefit.

02:01:15.540 | Now they didn't do the sixth group,

02:01:17.500 | which is really what I'm going to do some hand-waving about,

02:01:20.620 | which is the full stack, full fat method,

02:01:23.660 | where they said, okay, you're gonna do nap plus caffeine

02:01:26.700 | plus cold hand and face washing plus bright light.

02:01:29.660 | But if you were to put those together,

02:01:31.820 | my thought is that they're probably additive

02:01:35.460 | rather than simply just, you know, netting each other out,

02:01:40.180 | which means that if you really want to not just do a nap

02:01:43.500 | or a nap plus, which would be the caffeine nap,

02:01:46.700 | but the nap plus plus version, you can lean into this study.

02:01:51.180 | And the protocol there would be, you get into bed,

02:01:55.220 | you have your espresso shot before you turn the light,

02:01:58.260 | you swig it, go down, set your alarm for 20 minutes,

02:02:01.340 | you wake up, the caffeine is kicking in,

02:02:03.460 | you get over the inertia, you go straight out,

02:02:06.580 | cold hands, cold face by way of cold water,

02:02:10.700 | and then you get immediate daylight

02:02:12.980 | for five to 10 minutes outside.

02:02:14.980 | And at that point, you're really in a supercharged state.

02:02:19.020 | So that's if you, just because I know

02:02:22.420 | there's probably gonna be some audience members

02:02:24.300 | who are willing to give this a try

02:02:26.940 | or who really want to optimize.

02:02:28.940 | Don't give me, you know, what is good,

02:02:31.420 | give me the extreme very best.

02:02:33.860 | That's the only suggestion I would have based on that data.

02:02:36.780 | - I love it.

02:02:37.620 | And actually what you just described

02:02:39.140 | could easily be translocated to the period

02:02:44.020 | after waking from the nightly bout of sleep,

02:02:47.740 | although one wouldn't ingest caffeine

02:02:50.700 | prior to waking up for obvious reasons,

02:02:53.160 | but it would make good sense to me to wake up,

02:02:56.940 | obviously get sunlight in one's eyes,

02:02:58.980 | splash some cold water in one's face or hands,

02:03:01.320 | or get cold shower, cold plunge, caffeine or delay caffeine.

02:03:05.780 | I mean, it's essentially the same set of tools.

02:03:09.060 | And I think it really points to the fact

02:03:11.820 | that circadian rhythm, clearance of adenosine,

02:03:14.960 | temperature modulation, and of course,

02:03:18.860 | the way in which these interact

02:03:20.980 | are really the levers and knobs to modulate wakefulness.

02:03:25.180 | - Yeah, so there are,

02:03:28.500 | I think we've gone over this notion of naps,

02:03:31.020 | but there are ways that you can try

02:03:33.100 | to manipulate the nap system still.

02:03:36.100 | And there are ways that you can manipulate it even further.

02:03:40.620 | But I like what you're saying

02:03:41.700 | because it just comes back to the fundamentals.

02:03:44.140 | Let's forego the nap conversation,

02:03:47.140 | just go back to the morning routine.

02:03:50.380 | You're absolutely right.

02:03:51.460 | And think about the cold water and warm water.

02:03:54.060 | My guess is that very few people, when they go to bed,

02:03:57.500 | they wash their face and their hands maybe,

02:04:01.560 | they're probably not washing it with cold water

02:04:03.500 | before they go to bed.

02:04:04.660 | - Correct.

02:04:05.500 | - They're going to be washing it with warm water.

02:04:06.860 | Why don't they do that?

02:04:07.980 | And they just say, well,

02:04:09.020 | why would I splash cold water on my face?

02:04:10.780 | You know, it probably wakes me up.

02:04:12.500 | You ever thought about why it wakes you up?

02:04:14.460 | Part of it is that, you know, the shot of activation,

02:04:18.620 | but the other part is thermoregulation.

02:04:20.900 | And the opposite is what you want to do.

02:04:22.360 | If anything, you want to be warming your hands

02:04:24.660 | and your feet.

02:04:25.500 | And that's exactly what you've always done.

02:04:27.060 | You've always medicated your sleep onset

02:04:29.580 | by using warm water on your face and your hands.

02:04:33.060 | - Several times during today's discussion,

02:04:35.100 | we talked about polyphasic sleep

02:04:37.180 | and the different types of polyphasic sleep

02:04:41.660 | that we covered are, I wouldn't say conventional,

02:04:43.660 | but they're conventional-ish.

02:04:46.680 | What are some of the more esoteric

02:04:48.980 | or let's call them high-performance

02:04:51.520 | polyphasic strategies for sleep?

02:04:55.540 | - So we've spoken about polyphasic sleep

02:04:57.720 | in the natural way it occurs, which is during infancy.

02:05:02.720 | And sleeping like a baby means that you're sleeping

02:05:05.980 | in a highly polyphasic way.

02:05:07.960 | But probably around about the late 1990s, 2000s,

02:05:12.560 | with the emergence of the biohacker movement

02:05:15.720 | and the quantified self movement,

02:05:17.920 | there started to become a lot of chatter online

02:05:21.200 | about this notion of polyphasic sleep.

02:05:24.520 | And here, no longer are we infants, we're now adults,

02:05:27.720 | but we're engaging in a pattern that is highly polyphasic.

02:05:31.900 | Polyphasic sleep simply by definition,

02:05:35.400 | again, means that you're having multiple phases of sleep

02:05:37.520 | within a 24-hour period.

02:05:39.200 | And there are different strategies.

02:05:41.040 | So the way polyphasic sleep in adults works

02:05:43.400 | is that you take the 24-hour period

02:05:45.080 | and you think about it like a pie chart.

02:05:47.480 | And then you start to slice that pie up

02:05:49.980 | into these quadrants.

02:05:52.360 | When it comes to polyphasic sleep,

02:05:53.680 | the goal is to put insert multiple phases of sleep

02:05:58.680 | around the 24-hour clock rather than one single phase.

02:06:01.560 | But the thinness of those slices of the pie are very thin,

02:06:06.560 | leaving large thick slices of wakefulness in between.

02:06:11.560 | The notion that being that if you were to sort of

02:06:14.240 | just intersperse little soupçons of sleep

02:06:17.640 | in terms of these little thin slices of sleep,

02:06:20.440 | you can increase the amount of time that you're awake

02:06:23.360 | and you can increase all of the benefits of wake.

02:06:27.000 | So if you look at the, there is a website,

02:06:30.360 | I think it's called the Polyphasic Society.

02:06:33.720 | And there it's not a scientific society,

02:06:36.840 | like the psychological,

02:06:39.640 | the American Association for Psychology

02:06:42.680 | or American Medical Association or British Medical.

02:06:46.680 | It's not one of those ratified,

02:06:48.920 | certified scientific or medical.

02:06:50.920 | It's just a society that lives online, which is great.

02:06:53.900 | And they make claims to suggest that polyphasic sleep

02:06:58.520 | can improve aspects of your mood.

02:07:01.160 | It can improve aspects of your productivity.

02:07:03.920 | It can maybe even improve aspects of health.

02:07:06.240 | I think sometimes there are claims that it can help

02:07:09.000 | with lifespan.

02:07:11.480 | And there are a number of different schedules

02:07:15.000 | that they will describe to you

02:07:17.160 | and that you can find out there of polyphasic sleep.

02:07:21.240 | There is the first one that probably people have heard of

02:07:24.080 | is called the Uberman schedule.

02:07:26.480 | And by the way, there is no H at the start of that.

02:07:30.020 | It is simply U.

02:07:31.960 | I know it's not this man sitting across from me

02:07:34.920 | who has anything to do with this schedule.

02:07:37.600 | And after we discuss the data,

02:07:39.360 | he will reassert that very same fact.

02:07:43.000 | Then there's something called the Everyman schedule.

02:07:45.920 | And then there is the Triphasic schedule.

02:07:48.320 | And there's lots of different other flavors of this.

02:07:51.760 | The differences between them are

02:07:53.840 | in how you split up that pie chart

02:07:55.840 | and how much you assign to little thin slices of sleep

02:07:58.560 | versus longer periods of wake

02:08:00.200 | and how many of those you insert,

02:08:01.920 | but they all follow the same pattern.

02:08:03.960 | If you look at the literature, however,

02:08:06.400 | it didn't begin with the biohacker movement.

02:08:09.680 | The first description I can find in the human record

02:08:14.680 | comes from Time Magazine, an issue in 1943.

02:08:18.760 | And they describe the protocol of, at the time,

02:08:22.920 | a fantastic, very interesting designer,

02:08:25.560 | a guy called Buckminster Fuller.

02:08:28.120 | And he created a design principle.

02:08:30.880 | And that design principle

02:08:32.120 | was called the Dymaxion principle.

02:08:35.400 | The Dymaxion principle was principally used initially

02:08:39.640 | to build unique building structures.

02:08:42.360 | And it uses this notion of different sort of almost spokes

02:08:47.280 | that interconnect in a central hub

02:08:49.560 | that creates a self-supporting structure.

02:08:51.520 | The most obvious,

02:08:52.800 | have you ever been to one of those geodesic domes

02:08:55.920 | and inside you go in and it's sort of like

02:08:57.360 | a botanical garden and it's all tropical,

02:08:59.880 | despite you being in a,

02:09:01.280 | let's say being in England and London

02:09:03.080 | and it's beautifully tropical inside of there.

02:09:05.440 | That structure, that sort of lattice structure,

02:09:08.240 | that comes in part from his design.

02:09:10.840 | This was the Dymaxion principle.

02:09:12.960 | And he scaled it to different things.

02:09:15.200 | The Dymaxion car, the Dymaxion house,

02:09:18.080 | the Dymaxion dome, fascinating.

02:09:21.880 | But he was no fan of sleep.

02:09:23.800 | And he saw sleep as a rather significant waste of time

02:09:28.200 | when, just like the rest of his Dymaxion principle,

02:09:31.640 | he could be harnessing more efficiency out of the system

02:09:35.320 | with less structure and here less sleep structure

02:09:39.800 | inserted into his 24 hour period.

02:09:42.200 | So he was the first one to describe his schedule

02:09:44.800 | and it was called the Dymaxion schedule of polyphasic sleep.

02:09:48.680 | So it may have been a practice earlier in the record,

02:09:52.640 | but that's the earliest one I could find.

02:09:55.200 | So let's come back to the claims of polyphasic sleep,

02:09:58.360 | that it could improve, let's say your mood

02:10:00.640 | or your cognition or your productivity or your health.

02:10:03.760 | A group of scientists at Harvard,

02:10:07.720 | some of my old colleagues from Harvard,

02:10:10.640 | they looked at all of the literature

02:10:13.440 | on all of the studies that were polyphasic-like

02:10:17.520 | or testing this claim.

02:10:19.800 | And the first thing that they found

02:10:22.240 | was to their claims of improved cognition,

02:10:25.520 | productivity, mood, as well as health,

02:10:28.880 | they found no supportive evidence

02:10:30.840 | that polyphasic sleep was helpful.

02:10:33.800 | Then they turned the tables and they said,

02:10:35.480 | well, could it be hurtful?

02:10:38.320 | And in fact, that's exactly what they found.

02:10:40.880 | Firstly, the total amount of sleep that you get

02:10:43.280 | on any one of those schedules is decreased significantly.

02:10:46.120 | Now, of course, that's the goal.

02:10:48.040 | The quality of sleep that you get though is miserable.

02:10:51.960 | Your sleep efficiency,

02:10:53.760 | even when you're having these short periods of time,

02:10:56.040 | especially during the waking hours, is very poor.

02:10:59.480 | It's not a type of even short sleep that you would wish for.

02:11:02.960 | Third, they found that it would reduce

02:11:04.840 | your REM sleep amounts.

02:11:07.360 | So that was the first set of findings.

02:11:08.760 | Your sleep is no better.

02:11:10.600 | If anything, it's significantly worse.

02:11:13.160 | And then they started to find

02:11:15.240 | that there were significant impairments

02:11:17.240 | in many of those things,

02:11:18.360 | impairments in cognition, in judgment-making

02:11:21.280 | and decision-making, impairments in mood,

02:11:23.800 | and some aspects of impairments in metabolic health,

02:11:27.000 | particularly glucose regulation.

02:11:28.920 | So when it comes to polyphasic sleep,

02:11:33.120 | sleeping like a baby, if you're an adult,

02:11:36.040 | seems to be a rather unwise piece of advice.

02:11:39.800 | - Yeah, I mean, it probably goes along

02:11:41.360 | with eating baby food, drinking breast milk,

02:11:43.280 | and having somebody else clothe and change you as an adult.

02:11:48.280 | It's probably not advisable.

02:11:51.800 | It doesn't seem to be at least supported by the data.

02:11:56.760 | And again, I want to be so careful here,

02:12:00.440 | and you're very careful too.

02:12:02.840 | I'm not here to necessarily tell anyone

02:12:05.680 | absolutely how to live their life.

02:12:08.560 | I'm just a scientist, and all I can do

02:12:10.440 | is give you the information, just as you do,

02:12:13.400 | and then it's up to you to make the best decisions

02:12:15.680 | that you wish to make.

02:12:17.000 | All I would say is that I would hope

02:12:19.640 | that as long as you're not hurting yourself

02:12:22.680 | and harming your health,

02:12:24.000 | and you're not hurting other people,

02:12:25.800 | and it makes you happy,

02:12:27.880 | then I say, whatever it is in life, good luck.

02:12:30.880 | I embrace it.

02:12:32.360 | - I always say, do as you wish, but know what you're doing.

02:12:35.560 | And don't hurt yourself or anybody else.

02:12:39.080 | - Can you get me that T-shirt?

02:12:40.240 | And I will wear it five days through Tuesday.

02:12:42.840 | So here in this regard, though,

02:12:45.680 | I would say the evidence would suggest

02:12:47.560 | that maybe you're compromising your health

02:12:49.920 | and your wellness, but that's your choice,

02:12:51.520 | and I understand it.

02:12:52.360 | So again, no judgment.

02:12:54.040 | To the question, however,

02:12:55.240 | of as long as you're not hurting other people,

02:12:58.120 | here, I would say that there is a pause for caution,

02:13:01.640 | because what we know is that

02:13:03.480 | when you're not getting sufficient sleep,

02:13:04.800 | I described all of the health consequences

02:13:06.840 | in the first episode.

02:13:08.160 | There's another danger here,

02:13:09.800 | which is road traffic accidents.

02:13:12.200 | And we describe these microsleeps that happen

02:13:14.360 | and why car accidents that are caused by sleepiness

02:13:17.280 | can be so catastrophic.

02:13:19.080 | There's a very interesting study that was done

02:13:21.120 | where they looked at people getting less than six hours

02:13:24.080 | of sleep for several nights,

02:13:26.440 | and they put them into a driving simulator.

02:13:28.440 | And they asked, what is the probability

02:13:30.480 | that you have a crash or an off-road event?

02:13:33.920 | And sleeping less than six hours a night

02:13:36.760 | resulted in a 30% increase

02:13:39.200 | in you getting into a car crash.

02:13:41.760 | Now, the AAA released some data showing that

02:13:46.360 | when you get down to five hours of sleep,

02:13:49.360 | there is, I think it's something like two to three times

02:13:51.840 | higher likelihood of an accident based on real data.

02:13:55.120 | And then when you are on four hours of sleep,

02:13:57.360 | it was close to a 10 times greater risk.

02:13:59.960 | So in other words, the less and less sleep that you get,

02:14:02.480 | it's not a linear increase in your risk of a car accident,

02:14:06.080 | it's an exponential increase.

02:14:07.960 | So I bring this back to polyphasic sleep,

02:14:10.600 | because I don't know, think about that 30% study.

02:14:14.680 | Let's not go to the extreme, just less than six hours

02:14:17.080 | of sleep.

02:14:18.240 | If this evening you called a taxi,

02:14:22.280 | and it turns out two taxis turned up,

02:14:24.920 | and outside of your door, I said, look,

02:14:26.920 | one of these two, you can choose either one of them,

02:14:29.080 | but I'll just tell you that one of these taxis

02:14:31.400 | has a 30% higher likelihood of getting in a crash

02:14:34.080 | relative to the other, and it's this one on the right,

02:14:36.160 | which would you like to pick?

02:14:37.720 | Or which would you like to put your wife

02:14:39.200 | and children in to send?

02:14:41.440 | It's very obvious.

02:14:42.640 | So I raised that question just to be mindful.

02:14:47.200 | No one would wish to cause harm on someone else.

02:14:50.640 | To carry the harm of someone else by way of your own doing

02:14:54.480 | on your shoulders for the rest of your life

02:14:56.720 | is not one I would wish for,

02:14:57.880 | and it's not one that you would wish for.

02:14:59.800 | That's the only cautionary note.

02:15:01.640 | But other than that, I would say,

02:15:04.080 | sort of live life to the full.

02:15:06.680 | - Well, that brings us to the conclusion

02:15:10.400 | of yet another incredible voyage

02:15:13.600 | into the landscape of sleep,

02:15:15.560 | most notably the different phases,

02:15:18.320 | monophasic, biphasic, and polyphasic sleep,

02:15:21.480 | and naps and caffeine, and all of their interactions.

02:15:25.520 | These are such important topics at the level of concepts,

02:15:28.800 | at the level of mechanisms,

02:15:30.120 | and as you've also beautifully described,

02:15:32.560 | at the level of protocols,

02:15:34.360 | that is actionable tools that people can apply.

02:15:37.120 | So thank you ever so much, Matt,

02:15:39.760 | for taking us even further along this voyage.

02:15:43.240 | I'll just remind people that episodes one and two

02:15:46.440 | of this series that Matt is so generously providing

02:15:51.440 | information about sleep for us are out,

02:15:55.600 | and those can be accessed

02:15:57.200 | through links in the show note captions.

02:15:59.160 | Those fill in yet other mechanisms and aspects of sleep,

02:16:02.160 | and I'm also particularly excited

02:16:04.360 | for the fourth installment in the series coming up

02:16:07.720 | about the relationship between sleep, memory, and creativity.

02:16:12.160 | So just incredibly important topics relevant to everybody.

02:16:15.960 | I also just want to make note

02:16:18.360 | that I really appreciate you highlighting

02:16:20.320 | some of the developmental shifts that occur with sleep.

02:16:22.840 | I often get questions about, you know,

02:16:25.600 | sleep in children, and babies, and elderly adults,

02:16:28.800 | as well as all the ages in between,

02:16:31.040 | and you've just built this incredible tapestry

02:16:34.040 | of information for people to think about

02:16:36.320 | and act upon should they choose.

02:16:38.080 | So thank you, Matt, ever so much,

02:16:40.560 | and I look forward to episode four.

02:16:43.040 | - Andrew, thank you.

02:16:44.120 | It is such a privilege,

02:16:45.280 | and it remains just my absolute delight

02:16:47.560 | to be here with you.

02:16:48.480 | Thank you.

02:16:49.320 | - Thank you for joining me for today's episode

02:16:51.160 | with Dr. Matthew Walker.

02:16:52.680 | To learn more about Dr. Walker's research,

02:16:54.880 | and to learn more about his book

02:16:56.520 | and his social media handles,

02:16:57.800 | please see the links in our show note captions.

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02:18:44.600 | Thank you once again for joining me

02:18:45.920 | for today's discussion all about sleep

02:18:48.080 | with Dr. Matthew Walker.

02:18:49.680 | And last, but certainly not least,

02:18:51.720 | thank you for your interest in science.

02:18:53.720 | (upbeat music)

02:18:56.300 | (upbeat music)

Dr. Matt Walker: How to Structure Your Sleep, Use Naps & Time Caffeine | Huberman Lab Guest Series

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