- Welcome to the Huberman Lab Guest Series, where I and an expert guest discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today marks the second episode in our six episode series all about sleep with our expert guest, Dr.

Matthew Walker. During today's episode, we discuss the do's and the do nots of sleep. Focusing for instance, on how to use light and absence of light as well as temperature, both of your sleep environment, specifically the room you're in, your body temperature, and much more in order to regulate the timing and quality of your sleep.

And we discuss how things like alcohol, caffeine and cannabis impact sleep and the various stages of sleep. And we discuss the various tools that exist now and that are rapidly becoming available to improve your sleep. This episode is essential for anyone trying to optimize their sleep. And when I say optimize your sleep, I mean trying to optimize the formula that was addressed in the first episode of this series, which is the QQRT formula, the quality, quantity, regularity and timing of your sleep.

Four variables that combine to determine whether or not your sleep is optimized for you and thereby providing the most restoration and improvement to your mental health, physical health and performance. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford.

It is however, part of my desire and effort to bring zero cost to consumer information about science and science related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Helix Sleep. Helix Sleep makes mattresses and pillows that are customized to your unique sleep needs.

It's abundantly clear that sleep is the foundation of mental health, physical health and performance. When we're getting enough quality sleep, everything in life goes so much better. And when we are not getting enough quality sleep, everything in life is that much more challenging. And one of the key things to getting a great night's sleep is to have the appropriate mattress.

Everyone however, has slightly different needs in terms of what would be the optimal mattress for them. Helix understands that people have unique sleep needs and they've designed a brief two minute quiz that asks you questions like, do you sleep on your back, your side or your stomach? Do you tend to run hot or cold during the night?

Or maybe you don't know the answers to those questions. If you go to the Helix site and take that brief quiz, they'll match you to a mattress that's optimal for you. For me, it turned out to be the Dusk D-U-S-K mattress. It's not too hard, not too soft. And I sleep so much better on my Helix mattress than on any other type of mattress I've used before.

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Today's episode is also brought to us by Woop. Woop is a fitness wearable device that tracks your daily activity and sleep, but also goes beyond that by providing real-time feedback on how to adjust your training and sleep schedule to perform better. I've been working with Woop on their scientific advisory council to try and help advance Woop's mission of unlocking human performance.

As a Woop user, I've experienced the health benefits of their technology firsthand for sleep tracking, for monitoring other features of my physiology, and for giving me a lot of feedback about metrics within my brain and body that tell me how hard I should train or not train, and basically point to the things that I'm doing correctly and incorrectly in my daily life that I can adjust using protocols, some of which are actually within the Woop app.

Given that many of us have goals such as improving our sleep, building better habits, or just focusing more on our overall health, Woop is one of the tools that can really help you get personalized data, recommendations, and coaching toward your overall health. If you're interested in trying Woop, you can go to join.woop.com/huberman today to get your first month free.

Again, that's join.woop.com/huberman. Today's episode is also brought to us by Waking Up. Waking Up is a meditation app that has hundreds of different meditations, as well as scripts for yoga nidra and non-sleep deep rest or NSDR protocols. By now, there's an abundance of data showing that even short daily meditations can greatly improve our mood, reduce anxiety, improve our ability to focus, and can improve our memory.

And while there are many different forms of meditation, most people find it difficult to find and stick to a meditation practice in a way that is most beneficial for them. The Waking Up app makes it extremely easy to learn how to meditate and to carry out your daily meditation practice in a way that's going to be most effective and efficient for you.

It includes a variety of different types of meditations of different duration, as well as things like yoga nidra, which place the brain and body into a sort of pseudo sleep that allows you to emerge feeling incredibly mentally refreshed. In fact, the science around yoga nidra is really impressive, showing that after a yoga nidra session, levels of dopamine in certain areas of the brain are enhanced by up to 60%, which places the brain and body into a state of enhanced readiness for mental work and for physical work.

Another thing I really like about the Waking Up app is that it provides a 30-day introduction course. So for those of you that have not meditated before or getting back to a meditation practice, that's fantastic. Or if you're somebody who's already a skilled and regular meditator, Waking Up has more advanced meditations and yoga nidra sessions for you as well.

If you'd like to try the Waking Up app, you can go to wakingup.com/huberman and access a free 30-day trial. Again, that's wakingup.com/huberman. And now for my conversation with Dr. Matthew Walker. Professor Matt Walker, welcome back. We're all so happy to have you here. And in episode one, you beautifully described the biology of sleep, why sleep is important, what happens when we don't get enough sleep, and you incentivized getting adequate amounts of great sleep, and you defined what great sleep is, and you provided some excellent practical protocols and tools for getting great sleep.

However, today you're going to tell us, I believe, about the protocols for really optimizing one's sleep, both conventional tools and protocols and some, let's say, unconventional. Not heretical, but unconventional tools for optimizing one's sleep. So let's start with the basics. What are the basics of what I think I've heard you refer to previously as sleep hygiene?

- Yeah, I think many of us can resonate with the idea of dental hygiene, but it turns out there's something called sleep hygiene. And there are probably, I would say, five edicts of sleep hygiene. I offer them as tools and not necessarily rules because I don't think people respond to rules.

People respond to reasons and not rules. So if it's okay, I'll probably just unpack each one of them rather than just sort of bark them at you and hope people assume that it's the right answer. I'll explain the answer so people understand why it's important. So as I said, there are probably five things that you can start doing tonight to try to improve your sleep.

The first we've spoken a little bit about in that first episode, it's part of the four macros of good sleep. First piece of advice, regularity. Go to bed at the same time and wake up at the same time, no matter whether it's the weekday or the weekend. Regularity is king.

And the reason is because when you feed your brain the signals of timed regularity for your sleep, it will anchor your sleep and improve the quantity and the quality of that sleep. Because part of that signal of regularity going into your brain in terms of that repeated behavior, night after night sleep, in other words, helps train that central 24-hour circadian clock that we also spoke about in the first episode.

So that's the first piece of advice. Try to keep it as regular as you possibly can. The second piece of advice is darkness. In my view, we are a dark, deprived society in this modern era. And we need darkness at night, as well you've spoken about, to release a hormone called melatonin.

And melatonin will help time the regular onset of your sleep. So that sounds great, but boots on the ground, Matt, what does that mean? I would suggest the following. In the last hour before bed, try to dim down 50%, if not more, of your lights in your home. And you will be quite surprised at how sleepy and soporific that will make you feel.

I will do this in a regimented way. I have a little reminder that pops up and tells me now is the time to dim the lights based on your bedtime. And I'll go around and I'll shut lights down. In my bedroom, I will actually have a smart light bulb, and it is way down to probably as little as maybe five lux.

And lux is just a metric of the light. It's way down there, and it's also very deep orange, sort of red, and we can come on to why that's the case. So that's the first thing, even before you're thinking about sleep, start to decrease the light. For example, if you were there at, let's say, for a standard sleep schedule at 10 p.m., and normally you are getting into bed at 10, 30 p.m., but you feel pretty wide awake, if there was an electrical blackout and you lost your phone, magnetic too, phone goes down, lights go down, total blackout, my suspicion is that fairly soon you'd say, "Gosh, I actually feel quite sleepy." Whereas if the lights were blazing, you've got your phone, televisions on, lots of stimulation, you're probably going to think 10, 30, no, I could probably push through for at least another hour.

So try to dissipate that light. And then if you need to, wear an eye mask, blackout curtains, always good as well. But we need that darkness at night because when you give the brain the signal of darkness, it releases effectively a brake pedal. That brake pedal has normally been applied by way of light on the release of that spigot of melatonin.

And when you take the brake pedal off, it starts pumping out into the brain. You can also then, of course, probably reverse engineer this trick in the morning. And this is another component of why you've been, I think, such a wonderful advocate for light in the morning. It does many things, but one of the things that it does is reapply that brake on melatonin and therefore you lose the signal to your brain of darkness.

That's what melatonin in some ways is doing. We often call it the hormone of darkness or the vampire hormone. Not necessarily 'cause it makes you look longingly at people's necklines and want to bite in, which is great if you're into that, but it's really simply about it's releasing melatonin, which tells the brain, "My goodness, it's nighttime." But if you've got bright light on, you come from your office, you're driving home, so you've got artificial light during the day, which is probably not strong enough to stimulate you and bring you awake.

You come home and you've got, again, bright light, but it's still strong enough now to prevent the release of melatonin. You start to shift in your timing and you may have problems with your sleep. So that's the second piece of advice. I would love to ask you about that morning light too and the alertness benefits.

I'm, as a sleep researcher, more focused on the evening component of light and decreasing it, but you've done a great job. I don't know if there's anything- - There are a couple of quick points that are based on some, what I consider really nice studies. There's beautiful work in humans showing that bright light exposure in the morning, especially from sunlight, but if one doesn't have access to sunlight for whatever reason, there are commercially available so-called SAD lamps, Seasonal Affective Disorder lamps.

They range anywhere from 5,000 to 10,000 lux, very bright. But certainly morning sunlight viewing and lamps of the sort I just described have been shown to increase the amplitude of the morning cortisol spike by as much as 50%, five zero. So people hear cortisol and they freak out. They think that's not good.

I want my cortisol low, but you actually want your cortisol highest in the morning and lower in the afternoon and evening. And there's a lot of reasons for that elevated mood focus and alertness in the morning and throughout the day. And ease of getting to sleep at night, lower anxiety, lower depressive symptoms, and so on.

So that bright light also serves to control the amplitude of cortisol in the direction you want in the early part of the day. The other thing that's just more of a underlying dynamics of the circadian visual system, which is a system that I worked on for years, these wonderful cells in the eyes that are not for image forming, but rather for detecting sunlight and bright light for sake of setting circadian rhythm, is that the sensitivity of that system early in the day is actually quite low.

So you need a lot of bright light early in the day to effectively wake up your system and shut down the sleepiness signals such as melatonin. But later in the day, it's a rather diabolical system. It takes very little light, even from artificial sources, to disrupt your circadian rhythm and quash melatonin as little as 15 seconds of bright light in the evening.

I think Chuck Zeisler's laboratory at Harvard Medical School showed can quash melatonin in the evening. Now, I don't want people to freak out and think that if they go into a hotel bathroom, which oftentimes those are very bright, in the middle of the night, flip on the light that they're going to completely screw up their circadian rhythms.

But if I'm honest, they'd be much better off using their phone as a flashlight to navigate. People always say, well, wait, but the flashlight on the phone is very bright, but let's just get logical here. A light shown into your eyes, such as a flashlight, is very different than looking at a flashlight beam on the ground.

Far and away difference. So the point is that if you don't get enough bright sunlight or light in your eyes early in the day, and then you're indoors under artificial lighting, you might think, well, this is really bright lighting. This is the kind of lighting that could disrupt my circadian rhythm at night, and therefore it's sufficient to wake up my system.

No, early in the day and throughout the day, you need a lot of bright light, as much as safely possible to avoid sunburn and things of that sort, which you don't want. But then as the evening comes around, after sundown, you need very little artificial light in order to disrupt your circadian rhythm.

And then just very quickly, light from candles, fireplaces is okay. This is kind of interesting. It seems bright, but the measurements indicate that that's not gonna shift your circadian rhythm much. Candles are great, but of course don't burn your house down. So the orange and red tones in the evening way dim down, that's the way to go early in the day, bright, bright, bright light, as bright as you safely can tolerate.

- And what I like about, firstly, your mention of cortisol. You described how cortisol is rising in the morning, and that's a great thing, and it is a good thing. And in the evening, it's starting to drop. And if you look right around your prototypical bedtime, and we're going to speak later in this episode as to what your real natural bedtime is versus the one that you may be taking right now, it's very interesting.

Cortisol will almost hit its lowest point, something that we call its nadir, it's the lowest point in that trough of its decline right around the time when you should be sleeping. However, there's a great study that looked at people with insomnia. And in subsequent episodes, we'll discuss this too, but one of the ways that we think about or conceptualize insomnia is in two different flavors, sleep-onset insomnia, I can't fall asleep, and sleep-maintenance insomnia, I wake up, I can't get back to sleep.

And what they looked at was essentially cortisol levels. They had a catheter in the arm and they were sampling it from the bloodstream, and they were able to do that every 30 minutes. So it's a little bit like time-lapse photography, and you're getting a data point every 30 minutes across the 24-hour period, looking at cortisol across now a full 24-hour period.

And sure enough, when you look at healthy controls who can sleep well and insomnia patients, they look almost identical across the day. But then when it comes to falling asleep right around that bedtime period, the healthy controls are going all the way down. The insomnia patients go down and down and down, and then they have a rise back up right around that sleep-onset period.

And then they start to drop back down again just as the control group. But then they also often will have a spike in the middle of the night, which then comes down. And then both of them are staying low throughout the early morning period, and then it starts to rise back up.

So it's not as though net-net overall, there is a higher level of cortisol in people with insomnia. It seems to be right at those trigger zones that map very nicely to sleep-onset problems, sleep maintenance problems. - Very interesting. As somebody who wakes up in the middle of the night and sometimes has trouble getting back to sleep, that resonates.

I have no trouble falling asleep whatsoever. - Yeah. - Knock on wood. Superstitious about this at this point. But I use tools like non-sleep deep rest, yoga nidra, long exhale breathing. But, you know, and I think these wake up episodes seem to happen more when I'm processing a lot of stuff from my daily life.

- That's right. - You know, the unconscious brain oftentimes is working through things and will wake us up. - Yeah, I often think that sleep maintenance insomnia that you've just described is the revenge of daytime emotions unresolved. - That's a great way to put it, yeah. - So that would be, so we've spoken about regularity, we've spoken about darkness, and we've spoken about the inverse of that in the morning, which is light, a little bit of cortisol.

So the third out of the five is going to be temperature. And the advice here is keep it cool. As we mentioned a little bit in the first episode, and we will go into great detail when we speak not just about these conventional and unconventional tips, but we're also going to go into the future of science and where sleep science is taking us to, in fact, optimize and even enhance our sleep.

We will speak a lot about temperature. Suffice to say that you need to drop your core body temperature and your brain temperature by a little less than one degree Celsius, two to three degrees Fahrenheit to get to sleep and stay asleep. The general target that we have in sleep science, if you look across the literature, is somewhere around about the 67 degree Fahrenheit, or I'm trying to do the calculation, maybe 18.5-ish degrees Celsius.

Now I know that that sounds cold and cold it is, but you can also wear thick socks to bed. You can have a hot water bottle at the end of the bed. That's great too, but the ambient must be cold. The fourth piece of advice is walk it out.

And here, what I mean is do not stay in bed for long periods of time awake. And I think we mentioned this perhaps in the first episode too. When you are awake in your bed for long stretches of time, because your brain is an incredibly associative device, it will quickly learn that this thing called my bed is the place where I'm awake and not asleep.

And what you need to do is break that association. If you've learned that time and time again because you've stayed in bed, and the rule of thumb, and it's just a rule of thumb, about 20, 25 minutes, if you can't fall back asleep or you can't fall asleep, it's okay.

Just say, "Tonight is not my night. "It's not a problem. "Tomorrow is not completely shot. "It's fine. "I'm just going to get up, get out of bed." If you can, if you're lucky enough, try to go to a different room. And in dim light, read a book, listen to a podcast, whatever it is that relaxes you, just do that.

Don't check email, don't eat, because if you start eating, that again trains your brain to start waking up and feeding at that time. And only return to bed when you are sleepy. And there is no time limit for that. I don't want you to come back after half an hour when you are still awake and not feeling sleepy enough.

Why? Because you're going to get back into bed and be in the same problem again. And gradually, if you do this, and it's hard to do it, you will relearn the association that you had, I'm sure, as a child, which is that your bed is this place of sleepiness.

Because often people will be saying, "I feel so tired in the evening." And then they get into bed and they say, "But now I can't fall asleep at all. "I don't understand it." In part, it's because of that learned association. So that would be the fourth tip. The fifth tip makes me even more unpopular as a personality and character, which is try to be mindful of your alcohol and caffeine.

Now, in a subsequent episode, we'll go into great detail as to how caffeine works, its mechanisms, why it is sleep disruptive, and why, in fact, I've even perhaps changed my mind on caffeine and its benefits. But it also does have significant detriments to your sleep. So the rule of thumb here would be, try to cut yourself off from caffeine probably at least 10 or so hours before you expect to go to bed.

And you can just calculate back, calculate that. And try to limit it. So the dose and the timing make the poison. Cut yourself off after maybe two or three cups of coffee. And then that timing component, count yourself back, cut yourself off. Decaffeinated coffee, not too bad if you find the right thing to, if you need that fix.

Alcohol is probably one of the most misunderstood sleep aids, in quotes, that there is. It is no sleep aid at all. Now, if I didn't understand what I know about alcohol and sleep, I would think that too, which is, look, when I have a nightcap just before bed or two, even though I don't wear them, I may actually just fall asleep very easily.

It feels like I stay asleep very soundly across the night. So it's a great sleep aid and it really helps me. There are at least, I would say, three issues with alcohol. The first is that alcohol is in a class of drugs that we call the sedatives. And sedation is not sleep.

But when you take on board alcohol in the evening, you mistake the former for the latter and you think it helps you fall asleep. The second thing is that because it's sedation, or actually it's probably related to sedation, if I were to show you the electrical signature of your deep sleep when you're just sleeping naturally versus when you have alcohol in your system, it's not really the same.

It's not a naturalistic form of deep sleep. It mimics it, it looks not too dissimilar. But if I really do my analyses and I almost like that Pink Floyd album where I take the white light of electrical brain activity coming from your head as you're sleeping and split it apart into all of the different components, there are some components that are no longer present or some that are abnormally present.

The second issue with alcohol is that it fragments your sleep. So it will litter your sleep with all these punctuated awakenings throughout the night. The danger there is that many of those awakenings with alcohol you don't remember because they're too brief. But then you wake up the next day and you think, "Well, I didn't have a problem falling asleep.

I didn't have a problem staying asleep. But I just feel rough. I just don't feel restored by my sleep." And you don't add two and two together. The final concern with alcohol is that it's quite a potent blocker of your rapid eye movement sleep or REM sleep. And in subsequent episodes, we'll go into great detail as to the incredible learning and memory creativity benefits that come by way of REM sleep.

Also, it's essential for our emotional regulation and recalibrating our moods. So for all of those reasons, I would say two things. First, if you are struggling with sleep, not feeling restored by your sleep, keep in mind your alcohol intake. And also just in general, be mindful of that if you are thinking about your sleep and want to preserve it.

- So much of what you just said resonates. I confess that in my lifetime, I've had periods of pretty spectacular sleep. I characterize myself as somebody that could fall asleep anywhere, anytime. But I've also experienced the extreme challenges of sleep. And that relates to different things, life circumstances, et cetera.

In fact, recently, I've had some challenges with sleep despite using the protocols that I and others suggest. I hadn't heard some of the things that you're referring to here. And middle-of-the-night waking has become more of an issue. I communicated this to a former girlfriend of mine who I was in relationship with when I was a junior professor, meaning before I got tenure.

And she said, "You don't remember. You had a," Andrew, "But I do. You had a pattern back then of after I would fall asleep, you would continue working on your laptop," probably on Grants. "And then I would fall asleep working. And then according to her, I would wake up in the middle of the night and work a little bit until I'd get tired again and then fall asleep, and then this would repeat." So really stamping down the associative learning element that you talked about before.

So that was probably the first period of time in my life in which I created this rather deleterious association of work in the middle of the night in bed, right? And then more recently, I've had the experience of waking up, probably due to these like daytime things that I'm waking up in the middle of the night thinking about.

And now because of our discussion during the course of recording this series, I get out of bed after even 10, 15 minutes so that I can start to eliminate that association. And another piece is that I've always felt that when I get out of bed in the middle of the night because I can't sleep and I go to the sofa, I often can sleep very well.

And the reason being, right, it's a control experiment, proving that the location of sleep is... and the association of wakefulness and sleep in bed as opposed to on the sofa is a clear component. And this is in an environment that's of equal temperature. I mean, it's not a perfect experiment, right?

It's anecdata, as we say. But I think that the associative piece is, oh, so strong for many people. And so this is something to really take seriously. - I love that notion of people will often say, "I just get up, I go to the couch or the sofa, "and that's where I'll wake up in the morning." Also, they'll say, "When I travel and I go to a hotel room, "I just can sleep fine." Now, for some people, it's the inverse, but for those people, it's the contextual difference, meaning the change of the environment is so unfamiliar that it has not been bound to the association of wakefulness, it's related to sleep or at least the opportunity to sleep.

Sometimes even I've heard from some people, there's no studies or data on this, even turning yourself around. Now, this is hard if you have a partner in bed, but you just switch top to bottom of the bed and you take your pillow and you pull the duvet all the way down and you put the pillow at the opposite end where your feet used to be and you get into bed.

And even just looking around and sort of having a difference, that alone is so subtle, but it can make a real difference. So again, just keep these things in mind. I know it sounds strange or this whole sort of get up, get out of bed, break the association. And we'll come on to something.

Well, actually I'll come on to it now 'cause I think it's one of the unconventional tips and you mentioned it. A lot of people say to me, "That all sounds great. "Science makes sense." I just don't, it's dark, it's kind of cold. I really don't want to get out of bed.

So give me some alternatives. I think the single best piece of unconventional sleep advice I can give you is do anything that gets your mind off itself. The principal reason that if you look at insomnia as a physiological condition or current working model mechanistically of how insomnia plays out is that you are in this state of almost low level anxiety and you are somewhat stressed.

And when you go to sleep or you try to go to sleep or you wake back up and you try to get back to sleep, you just have this Rolodex of anxiety. In the modern world, we are constantly on reception and very rarely do we do reflection. And unfortunately for many of us, and I've been guilty of this, the only time we do reflection is when our head is placed on the pillow and we turn the light out.

And that is the last time you want to be doing reflection. That's the worst moment. And at that point, I think everyone can empathize with the idea of you turn the light out, you're under stress, your mind goes to those few things. In the darkness of night, thoughts become almost 10 times worse than they do in the bright of day.

And at that moment, you start to ruminate. When you ruminate, you begin to catastrophize. And when you catastrophize, you're dead in the water for the next two hours. So what do you do? The problem is, as I said, your mind is on itself and it's going through these repeated loops.

Anything you can do, for example, you can do some kind of a meditation. And when I was researching data for my book some years ago, I did look into meditation and I wasn't a meditator. I was a hard-nosed scientist. I didn't really kind of embrace with that notion or even that group of people.

But time and again, I read paper after paper and the data was very strong and it was coming from research groups that I respected very much indeed. So I thought, well, okay, I should probably give this a try. And that was six years ago. And since then, I now meditate for 10 minutes every single night before bed.

I do a guided meditation 'cause I'm not particularly skilled. So I use an app that moves me through that. But you can do whatever meditation you like. That's one example. The second example is you can do breathing methods because again, you're focused on your breath. And what are you not focused on?

Your thoughts. (laughs) And so anything that will allow you to explore some other focus, maybe it's a body scan where you start at the top of your head or you start at your feet and you work your way up and you just say, moving through now my neck, what sensations am I feeling?

Now into my shoulders, moving down into my chest now, I can feel the ends of my fingers. Am I sensing anything? And when you start doing that or any of these types of things, the next thing that you remember is your alarm going off in the morning because you got your mind off itself.

So I would say that that's probably one of the unconventional tips. But let me come back to the conventional. Anything else I've probably missed out or been unclear about there? Actually, I should probably say one thing in terms of these, they're not tips. I don't like the word. I know you don't either or hacks these are protocols and they're well-informed scientific protocols.

In all of this discussion today, you can get all of these things in place and still have problems with sleep. The reason is because you may be suffering from a sleep disorder. So the analogy would be, let's say that I'm your athletic coach and you're a sports superstar. I can perfect everything.

I can perfect your diet, your supplements. We can perfect your technique. We can perfect. But if you've got a broken ankle, none of those things are going to alter your performance right now. You've got to get to a doctor and get that seen to. And then we can come back to fine tuning your performance.

It's the same with sleep. If you've got a sleep disorder, such as snoring, sleep apnea, or insomnia, we need to get you to a doctor first. And then only after that, come back once you're resolved, then we can start to optimize. That's the only other thing I probably should mention.

- Yeah, this is all very useful discussion because I think that, of course, there will be those folks out there that just like, what are they talking about? I sleep so well. Consider yourself blessed. Many, many people struggle with challenges with sleep. And I think it's fair to say that sooner or later, most everybody experiences some challenges with sleep for whatever reason.

- You look at the statistics, that's highly likely in your lifetime, you are more than likely to go through either a period of challenging sleep, or in fact, a bout of insomnia. - I'd like to take a brief break and acknowledge our sponsor, AG1. AG1 is a vitamin mineral probiotic drink that also contains adaptogens and is designed to meet all of your foundational nutritional needs.

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- Yeah, many people do enjoy it and we're not calling judgment on them. I mean, certainly much of the world enjoys alcohol. Could we talk a little bit more about, aside from demolishing REM sleep, do we know that alcohol causes these disruptions in sleep directly, meaning by changing the pattern of release of neurotransmitters like GABA, things of that sort, or is this an indirect effect?

Is this like through the gut microbiome that then impacts sleep? And the reason I ask is maybe we could get to some more specific do's and do not protocols. So for instance, if somebody wants to have a cocktail, how close to sleep can they get and not diminish their rapid eye movement sleep too much?

You know, because people are still going to want to drink. And with that said, if people do have a couple of drinks and then they go to sleep, is there anything they can do prior to sleep to try and rescue some of their quality sleep? - Great question. So in terms of the mechanism, it seems actually not to be the alcohol, but some of the metabolic by-products of alcohol.

We think that perhaps the main culprit may be some of the aldehydes that are the metabolic separate consequences of alcohol metabolism. You make a good point though, in terms of the dose response timing curve, how late or how early do I have to cut myself off from alcohol? People have done those studies and they have found that even an afternoon single glass of wine, if you measure sleep in the way that we measure it at Bicenter with high fidelity, you can see compromises and impairments.

I wish I could tell you otherwise. I would say that based on that data, the principal protocol advice I would have for you is go to the pub in the morning. That way, by the time you're about to sleep, the alcohol is out your system and you could... No, no, I would never.

As a public scientist, I would never advocate necessarily for morning. I'm just kidding you. But that's sort of one of the unfortunate consequences that does seem to be an impact. To say that there isn't is just me not being truthful about the data. But again, if you think about the trade-off here, if you're going out or you're having friends over and you're gonna make an incredible evening of memories and you're going to open a favorite bottle of wine and have a couple of glasses of wine, is your sleep going to be compromised?

Yes, it is. But maybe that's worth the trade-off for that specific night. I would just not wish you to... And you've spoken a lot and so has our dear friend, Peter Attir and others. There just doesn't seem to be any safe amount of alcohol. But I would say, think about that trade-off simply.

However, don't make it a habit that you're doing it multiple nights a week or more. That would probably be the advice. - Great. What about food and sleep? How close to sleep is it okay to have a meal if you want to optimize your sleep? I like to eat my final meal somewhere around 6.30 p.m.

And I go to sleep somewhere around 8.30, 9 p.m. In an ideal world, sometimes I go to sleep a bit later. Sometimes I eat a little bit later. It's just, there's some variability with these. But put differently, what is the relationship between food intake and sleep quality in terms of timing of food intake?

And then perhaps we can talk a little bit about food macronutrients. - It's very interesting. There was somewhat of a dogma out there that we have to stop eating three or four hours before bed for optimal sleep. If you look at the data, the data is quite a spread, no pun intended.

There are some people for whom that works very well. And if they eat even two hours before bed, they just get disrupted in terms of their sleep. Some of that is about people just feeling too full and not feeling comfortable. Other aspects are that when you become recumbent, when you lie down, you have a higher risk of gastric reflux coming back up and therefore you get heartburn and that's pretty miserable.

And people will describe that too by way of closer proximity of food intake relative to when you're falling asleep. Nevertheless, if you look at the data, and I did a recent very deep dive on this personally myself about 12 months ago, it's not quite as extreme as the dogma makes out.

If you eat two hours before bed on average, it doesn't seem to necessarily harm your sleep. Now that's very different than saying what is best to improve or enhance your sleep. But the way these studies were designed, it was looking at detriments. They then went to 90 minutes before sleep onset.

And even there, there didn't seem to be marked impairments. 60 minutes, you started to see maybe some signs, but on average, the effect size was somewhat weak. But then when you get close to sort of 45 minutes or so, then things did start to deteriorate. I think it depends hugely on your chronotype and also just on your appetite, circadian rhythm preferences too.

I am someone who I do not feel very hungry when I first wake up in the morning. I don't feel very hungry throughout most of the day. And I will onboard most of my calories probably in the hours, probably in about a four-hour period, maybe less, even three-hour period.

And then I will cut myself off about 90 minutes before sleep. So classically, I would have been considered as violating this sleep dogma of cutting yourself off at least three hours. I think it's very personal though. Just experiment with it. You will know the situation. As for macros and specific food components, the data is a little bit mixed.

Certainly what we know is that if you're eating a diet that is high in sugar and low in protein, your sleep is worse. Why would that be the case? Well, one of the reasons that we think is that if you onboard sugar, it can be somewhat metabolically active. And when it becomes metabolically active, it can increase your body temperature, your core body temperature, even just very subtly.

But that's enough to disrupt your sleep as we spoke about with temperature. But I think in terms of really the... what would be the ideal macro-nutrient and even micro-nutrient dietary recommendation that I would have for you, I don't think we have enough data yet above and beyond that statement.

Yeah, I've experienced when I eat a very low-carbohydrate diet, which I've experimented with in the past, maybe even full ketogenic diet for brief periods of time, although I'm an omnivore, so I eat meat and eggs, and I also eat starches, pastas, rice, et cetera. But we know, based on beautiful work from, for example, Chris Palmer from Harvard Medical School, who is a guest on this podcast.

I listened to that. It was a great podcast. Yeah, Chris is spectacular and has advocated the exploration of ketogenic diets for the treatment of various psychiatric conditions, not all, but psychiatric conditions. And it seems, and he agreed with me on this, that when people go on very low-starch, very low-carbohydrate diets, that sometimes they can experience a bit of hypomania.

Some people can and challenge this with sleep. And sometimes there are psychiatric reasons why people stay on those diets anyway, and then they have to do other things to encourage their sleep, either pharmacology or supplementation or some combination. But I can say anecdotally for myself, if I don't eat starches for a extended amount of time, a couple of days, I find it very hard to get quality sleep, as indicated by sleep trackers, and just latency to fall asleep is longer than it is, et cetera.

So, I've opted to eat most of my carbohydrates later in the evening, which kind of violates every rule of eat your carbs early in the day. And I think there are some data to support that eating carbohydrates early in the day may actually have certain benefits for weight maintenance or weight loss.

So, I realized that, but those aren't my goals at the moment, weight maintenance, yes, weight loss, no. So, I think I've certainly feel after eating a dinner that has a bit more starch, pasta, rice, these things of that sort, and a little bit lower protein as opposed to the inverse, like eating a couple of ribeye steaks and a salad, but no starch, that my sleep is substantially better.

And I always attributed that to the relationship between some of these starches and the tryptophan/serotonin pathway. There is some data on that with the carbohydrate intake in the evening. And of course, that tryptophan and that carbohydrate intake will contain the precursor ingredients to something else that we've spoken about, which is melatonin.

And so, that may actually help healthily boost that melatonin signal. And there's a little bit of data on that to support it too. We also did a study where we were looking at night-to-night-to-night sleep and carbohydrate intake the next day. And it did seem to support what you're describing in terms of some of the carbohydrate benefits.

We also found a strange result that was almost the opposite prediction that we made, carbohydrate intake in the morning to equally help people wake up. And we were a little bit uncertain as to why, but we're going to go into more detail. The reason that you mentioned the suggestion of not to take on carbs in the evening is in part based on the evidence that your body's ability to dispose of sugar and obviously when you're eating carbohydrate you can have a higher spike of sugar.

Now that in part depends on what you're eating with that carbohydrate and also of course the nature of that carbohydrate, whether it's simple or whether it's complex, whether it's simple sugars versus complex more starchy carbohydrate. But the idea is that your body, even if you were to eat the same amount of carbohydrate in the morning, in the afternoon or in the evening, same carbohydrate dose and type, but your body's ability to dispose of that without having excessive spikes of glucose is worse in the evening, better in the morning, i.e.

if you're concerned about your blood sugar and your metabolic health, maybe that's what you should do. I think that that data is unclear on the basis of if you are glycemic normal, meaning that you currently do not have signs of type 2 diabetes or you're not prediabetic, then that may not necessarily be the case.

And so I think that's why it could be beneficial for you and I know that you think deeply about that. I've even been tracking blood sugar as well, I don't have any signs of that, but I'm just fascinated by some of that data and how it interacts with my sleep because I'm a sleep nerd.

So I think right now we just don't have plentiful data to recommend a particular sleep "diet" for improved optimization. I would say though that we can be a little bit more relaxed about the timing of our food. Earlier you mentioned caffeine and caffeine is a topic that we get into substantial depth in episode 3, but there and now I will emphasize that caffeine is the most commonly used drug worldwide.

I think the statistics says that 90 plus percent of adults consume caffeinated beverages every day, which is remarkable. And a few years back, I recall there was an article in The Economist that charted the countries for which the caffeine consumption was highest. And way out on the peak, peak, peak of almost triple or quadruple what the second place country consumed each day was, can you guess the country that consumes the most caffeine?

Could be tea, coffee, any form. I'm going to suggest it's a Scandinavian country. No, but they're up there. It was Switzerland. Now, I don't know if that's still the case, but apparently the Swiss- - The reason I went, I was thinking it was, because I've seen the graph, I was thinking it was Sweden, but hence the Scandinavian.

- And if I have that wrong, certainly someone will put it in the comments on YouTube. - No, I'm sure you're right and I was wrong with Sweden. - But as I recall, the Swiss drink so much caffeine. They have a lot to think about. So I love caffeine.

I drink black coffee, black espresso and yerba mate. I love yerba mate. I've been drinking it since I was a little one because of the Argentines in my family. And I drink it in the early part of the day, typically a couple hours after waking or so, I'll have my first sip of caffeine.

And then I try to stop drinking caffeine somewhere around noon or 1 p.m. Occasionally, I'll have a shot or two of espresso in the early afternoon if there's important work to be done and I need to do that. But I've noticed that even that can alter my sleep in ways that I don't like.

But that afternoon coffee, for some reason, tastes so much better than the morning coffee for me. I don't know what it is. So it's coffee, yerba mate packed early into the day and a lot of it for me. I have a high tolerance for it, but then I let it taper.

Is that an optimal contour of caffeine intake? Would zero caffeine be better if someone's just really committed to sleep and they don't like caffeine? Would zero be better than any? And what about that afternoon coffee or tea containing caffeine? I mean, how disruptive is it for sleep? - So the profile that you described, which is high peak early on, first thing when you wake up and then tapering off nicely down into the sort of early afternoon, ideal.

That sounds great to me. As for that afternoon coffee, it really depends again on when you're expecting to go to sleep. Now, for someone like you, I would say I would love to look at abstaining from that or just switching it out to, if you're using these pods or however you're brewing it, let's just switch it out and do an experiment for two weeks.

And we will look to see how much is that afternoon coffee really impacting your sleep? And we'll track your sleep with some degree of high fidelity with a wearable. And let's test that hypothesis because you go to sleep quite early. You are an early bird, maybe bordering on an extreme early bird.

And we'll speak about, we have spoken about those different flavors of chronotype. I would prefer you not to be having that caffeine in the afternoon based on how early you go to sleep. And I mentioned that preference because of what you described regarding your sleep maintenance insomnia. One of the issues with caffeine is that not only can it make it more difficult for you to fall asleep, which you don't have in part because if you're waking up quite frequently throughout the night and struggling to get back to sleep, you're going to be carrying a sleep debt into every night and that debt continues to grow.

And it's almost like compounding interest on a loan. So you will not have a problem falling asleep. In fact, sometimes the speed with which people fall asleep and some of these sleep trackers will almost penalize you for falling asleep too quickly is because in sleep science and clinical sleep medicine, if you're, it should take you somewhere, healthy sleep onset, five to 15, 20 minutes.

But if you put your head on the pillow and you turn off the light and within a minute or so, you're dead to the world and you're gone. I'm exactly, I'm worried that you're A, carrying a sleep debt. Now, not necessarily, but I would like to explore it with you.

And then I would say, even if you can fall asleep fine, this factor of waking up in the middle of the night is also related to caffeine. Why? Because caffeine not only can make it harder to fall asleep, not your problem, but it keeps you out of that deep, deep sleep.

And it puts you into a more shallow state of non-rapid eye movement sleep. And when you are in the shallow state, it's A, easier for you to be woken up, but B, and I think more of the problem, it's harder for you to fall back asleep because your brain doesn't necessarily want to go back down into that deep sleep and nor has it come up out of that deep sleep.

So you're not in that wonderful, glorious, thick, treacly sort of sleepy state. When you wake up, you go to the restroom, you come back and you just know, oh, this is gonna be great. As long as I can fumble my way back to my mattress, I'm gonna be asleep within another two minutes going back to it.

Whereas for you, you probably wake up and you feel pretty wide awake. I would like to see what happens when we negate that afternoon coffee on the frequency and the duration of those middle of the night awakenings for you. - Yeah, I'm definitely making the effort to avoid caffeine intake in the afternoon.

And I think I'm already starting to see some of the positive benefits of doing that as evidenced by the days that I consume caffeine in the afternoon and experience the deficits. It's a real thing. And I believe you've about the numbers on a different podcast previously. Talk a little bit about the metabolism of caffeine and maybe even some of the variations that exist between people in terms of the metabolic regulation of caffeine.

So how long, let's say drink a standard cup of coffee or a couple of espresso and it has a, gosh, I don't know, 150 milligrams of caffeine. Is that 200? - Yeah, it could be 150, 200. - Yeah, let's say 200 because certainly a barista these days is gonna draw a beverage that's- - They're gonna over-index.

- Yeah, so let's say 200 milligrams and somebody consumes that after lunch at 1 p.m. and their bedtime is, let's make them more conventional than I, somewhere between 10 and 11 p.m. Okay, so they're about- - Nine to 10 hours. - Nine to 10 hours out from their bedtime.

They're having a nice strong, quote-unquote, nice strong cup of coffee after lunch. What does that look like in terms of their biochemistry and impact on sleep? So caffeine has something that we call a half-life of about five to six hours, meaning that after five to six hours, about 50% of that caffeine is still circulating in your bloodstream and thus your brain.

That means that caffeine has a quarter-life of somewhere between 10 to 12 hours. Now this is on average and we'll come back to variations, but think of it this way. If you're taking a cup of coffee, like you described there, at midday, and then you're going to bed at, let's say, 11 or midnight, that would be the equivalent, based on what I've just told you, the quarter-life of getting yourself into bed.

And just before you took yourself into bed, you swig a quarter of a cup of coffee and you hope for a good night of sleep. And the chances are that it may not happen. Now, again, that's a little bit sort of hyperbolic as a statement, but just try to conceptualize it in that way.

You would never think about taking on a last quarter of a cup of coffee just before you put your eye mask on. - No, but I have some friends and somebody actually who works with the podcast team, and we'll go out to dinner as a team when we're on the road and he'll order a big coffee right after 9 p.m.

dinner. And I'm like, "Can you sleep?" And they say, "Oh yeah, no problem." - And that no problem is in part this, I don't have an issue with falling asleep, but if we were to, based on the data, map their electrical brain activity, you would be able to see this reduction in the deep non-REM sleep.

And it can reduce it, if you look at the data, somewhere between 15 to 20%. Now, for me to reduce your deep sleep by 15 to 20%, I would probably have to age you by about 20 to 22 years. Or you could just do it every night with a late night coffee, should you wish.

So again, and maybe we'll speak about this in later episodes, I have changed my mind on caffeine. I think morning caffeine use, or coffee, I should say, being more specific, is fine because I think there are health benefits and we can go into in subsequent episodes why coffee and the coffee bean itself can provide those benefits.

So I've become a little bit more bullish on morning caffeine but evening caffeine, I just think the data is just not supportive. Even if you are, and there are variations and you were very astute in your question, some people, I said, on average, caffeine has a half-life of about five to six hours.

For some people, it's quicker. And for other people, it's slower. Why is that? It's based on a gene and we know the gene. It's a gene that is part of a set of liver enzymes. And the gene is called the CYP1A2 gene. And there are variations in that gene, what we call polymorphisms.

And you can do these genetic tests that you can buy these kits and they will probably tell you which you are. Are you sensitive or you're not sensitive? You probably already know. (laughs) And so some people will not be as sensitive and therefore they can have a more compressed timeframe of a half-life because it's moving out of their system in a quicker manner.

So again, I'm not trying to be scaremongering. I think you can have coffee in the morning and you'll be just fine. That late night coffee, I would like to see you obviate that if you are someone who's doing it. - And the afternoon coffee sounds like, maybe only every once in a while and try and make it mostly decaf or decaf for that matter, if it's really just for the taste.

- Yeah, if it's just for the taste, go decaf. If it's not, I understand that in some ways what I'm talking about is the ideal world and drum roll, it turns out that most of us don't live in that. We live in this thing called the real world. (laughs) And so if you are facing a circumstance where if you're under pressure at work or if you're a high-performing athlete and this is it, this is the event, it's all or nothing, understand that you are going to sacrifice some sleep at night, but maybe that sacrifice is well worth it.

So again, I'm very open-minded. I'm not trying to be simply too rigid with this. - I wanna take a brief break and acknowledge our sponsor InsideTracker. InsideTracker is a personalized nutrition platform that analyzes data from your blood and DNA to help you better understand your body and help you reach your health goals.

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If you'd like to try InsideTracker, you can go to insidetracker.com/huberman to get 20% off any of InsideTracker's plans. Again, that's insidetracker.com/huberman. So you've talked about alcohol and its effects on sleep. You've talked about caffeine and its effects on sleep. And we talked about food and its effects on sleep.

What about THC and CBD? Sometimes they're referred to more generally as cannabis. And it's interesting, gosh, when I was growing up, cannabis was illegal. Nowadays it's either legal or tolerated or decriminalized in many places, not all. But I would say there's been a tide shift in terms of cannabis, meaning that many people consume cannabis who are consuming it legally and consume it for a lot of reasons that other people consume alcohol, in a sedative effect, a slight hypnotic effect.

I mean, the actual definition of what these drugs do, it goes by certain terms in the psychiatric literature, of course, but in order to quote, unquote, mellow out, to feel more relaxed, to reduce their anxiety, it's far and away different than when I was growing up where, I mean, you would get into a lot of trouble if you were caught smoking a joint or taking a bong rip in the middle of the day.

And I realize most people aren't doing that at work. I guess it depends on where you work. But you know, edibles, tinctures, I mean, the consumption of THC and CBD is quite robust in a lot of places. So with all the issues of legality and the fact that young people should not be consuming them, I mean, people 18 and younger, not just for legal reasons, but the brain is still developing.

What is the story with THC, CBD, cannabis, edible, smoked, tinctures, on sleep specifically? - It's very interesting if you look firstly at the motivational reasons why people use cannabis. Based on the published study, somewhere in the top two reasons, sleep. - To fall asleep. - To fall asleep and stay asleep.

Obviously, usually the principle first reason is just to get high and have the experience and the pleasure of being high, if that's what sort of floats your train. But certainly it's sleep as what we call a hypnotic to put you asleep from the Greek derivative of the God for sleep.

That is high among the reasons that people will use. We currently don't recommend it. And here is why. Certainly THC helps you fall asleep faster. Very clear in the data. The problem is that first you start to develop a tolerance and to get that same sleep onset benefit, you need to get use, I should say, a higher dose.

So you start to develop dependency and your dose regimen starts to increase. The second issue with THC is that it's very good at blocking your dream sleep, your REM sleep. And in fact, many people, when they come in, they tell me, look, I was a heavy cannabis user, even a light cannabis user for some time.

And then I stopped using. And one of the strangest things happened to me. I just started to have the most wild, vivid, crazy dreams. And I didn't know what was going on. And it's a very simple explanation. As you've been using, your brain has been compromised in the amount of REM sleep it's been getting.

And you've been building up chronically a REM sleep debt. And your brain is smart in the sense that it does try to clock to some degree a counter of how much REM sleep you've lost. And many people will say, yeah, I don't really remember my dreams when I'm using.

But when they stop, the brain finally, because it's been cleansed of the thing that's the roadblock to REM sleep, not only do they go back to having the normal amount of REM sleep that people would have, they have that, plus they have what we call a REM sleep rebound, which is even more and more intense REM sleep, which leads to more intense dreaming.

So it's a very, I suspect there's a lot of people who've had that experience listening if they have been users and they've stopped. So that's the second reason we don't advocate it. The third reason is that when you stop using, you also go through a very vicious insomnia withdrawal syndrome.

Often many people will do. Now that depends on how much you've been using for how long you've been using. If you look at the data, and by the way, part of the clinical diagnostic, the psychiatric diagnostic description of cannabis withdrawal is insomnia. That's how reliable this insomnia problem is when you come off cannabis.

And if you look at the data, one of the main reasons that people relapse and start using cannabis again, even though they don't want to, is because they can't deal with the insomnia that withdrawal has given them. So you don't want to get into that vicious cycle. Should you wish again, it's your choice.

So THC, I think is not to be advised right now. CBD is interesting. I don't think there's enough data yet for us to have a very strong opinion, but I can at least offer mine. The data so far is a little bit mixed in what we call the effect size.

In other words, how reliable and how powerful is the benefit of CBD on sleep, but it does seem to have some benefit. What's interesting is that it doesn't seem to have the detriments that I just described for THC. You've got to be looking at the data a little bit careful with CBD.

It has what's called a U-shaped function to it, which is that if you're taking too little, and again, I really am so mindful of not trying to be, okay, here are the numbers, but if you look at them, I would say, kind of cross your eyes, squint your eyes, maybe less than 25 milligrams, you run into the danger of CBD being wake promoting rather than sleep promoting.

But once you get past, if you look ish, 50 milligrams and above, then you start to go in the opposite direction where it seems to be sleep promoting. And I mentioned that just because at least here in the United States and in many places in the world, that industry is not regulated.

So it may say 50 milligrams on the bottle. You don't really know how some of those companies will have what's called third party laboratory testing where they'll send it out and you can scan a QRI code and you can look at an independent laboratory that tested it and show you the purity of it.

So that may be one way to go. So CBD, I think has some favorable evidence right now. If that's the case, let's just assume that you and I speak in another five years time and there's really good data now for this. What could be the mechanisms? I think there's probably at least two, maybe three mechanisms.

The first is an indirect mechanism. CBD has been demonstrated very nicely in some fantastic studies to be an anxiolytic, which is a fancy term for saying it reduces down your anxiety. And earlier you and I discussed that anxiety and stress is one of the things that will keep you awake.

So indirectly it removes this kind of gate that is preventing you from moving down the Royal road of sleep. And it opens back up the gates because it's removed that gate mechanism, which is high anxiety. And by way of being an anxiolytic, it's soften that anxiety and it's easier for you to fall asleep.

I think that's probably the principle mechanistic bet I would have right now. Another indirect mechanism. If you look at some of the studies in rats and we do human work at my sleep center. So we don't do animal studies, but if you look at the data in the rats, CBD can be hypothermic, which means that it drops your core body temperature.

And just as we spoke about in earlier in this episode, you need to drop your body temperature to get to sleep. So I think that's the second reason. I think the third reason is that it could have a direct sleep promoting mechanism. I think it's unclear right now exactly how it's interacting with the sleep machinery of the brain.

We've got some hypotheses. The danger is, again, it's just not a well-regulated substance. So I am actually just full disclosure. I'm working with a company in the United Kingdom in collaboration with King's College and the Institute of Psychiatry there to see if we can create an analog, a clean analog of CBD.

But I think the potential upside of it, not just for sleep, but for a number of different psychiatric conditions like anxiety could be beneficial. So I would say that that's right now the sort of the skinny on THC and CBD. - Okay, so just to make sure that I have the basic list of sleep hygiene factors, correct.

I have regularity is king. - Yep. - Light and dark, meaning that one should optimize or at least seek to optimize their exposure to light in the morning and throughout the day and then in the evening to make things dim and dark. - Yes. - Temperature. And there you have, it's not a mantra, but what is it?

It's a warm up to cool down to fall asleep. And then it's stay cool, like Fonzie, stay cool to stay asleep and then a warm up to wake up. - Yep. And we will come onto that I think in a little while again. - Then there's walk it out, which is if I understand correctly, if you're trying to fall asleep or fall back asleep and it's taking you longer than about 20, 25 minutes, you should just get out of bed and go elsewhere in the house, do something else.

Maybe even lie down on a different surface in the house to try and see if you can sleep there, but don't stay in bed. Don't create a paired association of wakefulness and your bed, because that can lead to problems in subsequent nights. - Yeah, and I would only say that try to resist if you can, if you really want your bedroom to be the place where you now become consistently asleep, try not to start sleeping in some other location consistently because then all of a sudden you bond that with good sleep and you unbuckle this notion that we're trying to relearn, which is no, your bedroom is the place of sleep.

So it's fine to go elsewhere. Try to stay awake and force yourself to stay awake until you are absolutely sleepy, then go back to bed. - Okay, and then we discussed alcohol, food, caffeine, and THC/CBD, aka cannabis. And with respect to alcohol, it's clear that none is best if you're going to have some, you don't want to drink too early in the day, but you don't want to drink too much or too close to bedtime because it can disrupt rapid eye movement, sleep.

Food, it seems that creating some sort of buffer between your last bite of food and your to bed time by, anyway, somewhere between, you know, maybe two, three hours, but for some people it'll be more like 90 minutes. And of course that's going to depend on the size of the meal, et cetera, but eating a big meal and then going straight to bed, probably not a good idea.

Caffeine has this long half-life. So if you're going to indulge, which I do, do so early in the day. Beware of the afternoon caffeine. - Yeah, do the Huberman taper is what I'm going to call it right now, which is not an interpretive dance. It's simply the caffeine tape.

- And then THC/CBD does nothing good for your sleep architecture. Although some people have the impression that it is good for their sleep because it makes it easier for them to fall asleep. But what they're unaware of is that it is disrupting the quality and architecture of the different stages of sleep in ways that are not serving people well.

- That seems to be the case for THC. And I think CBD, you know, has promise and research must try harder, including my own. - And you very kindly emphasize that you're not telling people what to do. They just should know what they're doing so that they can make changes if they so choose.

- That's right. I would always say that I'm not trained to be a medical doctor. Any advice that I give is simply scientifically descriptive advice. It's not medically prescriptive nor lifestyle prescriptive advice. - I'm smiling 'cause what I always say is I'm a scientist, not a physician. So I don't prescribe anything, but I profess lots of things.

Whereas my good friend, who's a musician, Tim Armstrong says, "I'm not a cop." - That's right, so do what you want. Okay, what a wonderful list to leap off into the unconventional and more advanced tools for sleep enhancement. So let's go there. - So I think many people may have heard of some of the conventional, but what about the unconventional?

I would probably offer five or six. The first one I would say is that if you are struggling with sleep and you have had a bad night of sleep, the first recommendation is do nothing. And what I mean by that is if you've had a bad night of sleep, you're awake for three hours, do not sleep in any later into the morning.

Do not go to bed any earlier. Do not increase your caffeine intake to try to offset it. And do not nap during the day. Why am I telling you those things? If you wake up later that following morning, your adenosine clock that we spoke about, this building up of sleepiness that happens when we wake up, is going to start later in the day.

So when it comes time for you to fall asleep at what would then be the next night at your normal time, you're not going to feel as sleepy, why? Because you woke up that much later and you're setting yourself up for failure again. Equally, don't go to bed any earlier.

If you have become accustomed and your brain has, and your circadian clock has become accustomed to going to bed at a certain time and hopefully you're doing it regularly, then getting into bed two or three hours early has the danger, it's not a certainty, but a danger of you then getting into bed and thinking, well, I know I had a bad night of sleep last night, but I still can't fall asleep straight away.

So now you're spending another 90 minutes in bed at the beginning, 'cause you've gone to bed 90 minutes earlier thinking it's a good idea to compensate. Don't do that either. Hold out, even if you do feel tired, my recommendation would be after that bad night of sleep, hold out for as long as you can, as close to your natural bedtime as possible, then go to sleep and you will give yourself highest chance of success.

Don't over-caffeinate, that's the obvious one, follow the beautiful Huberman taper, and then obviously try not to compensate with a nap. Why? Because that nap, as happens when we sleep, is going to remove some of that sleepiness, that adenosine, and once again, you get into bed and you're not as sleepy as you would naturally be.

So you again go through a bad night 'cause you're struggling to sleep, or you wake up and you can't get back because you've got less weight of sleepiness on your shoulders due to the nap that happened earlier. So I know it's hard, but I would say when the alarm goes off after a bad night, you just think, I do not want to get up, it's been such a rough night.

I know it's a short-term gain, but trust me, it's a long-term loss because you're going to then just get into this vicious cycle. So that's the first unconventional tip. - Can I just pause you for a second? I'm a little wide-eyed over here because I did not know any of that.

Typically, if I get a poor night's sleep, I'll do whatever I can to recover that sleep, take a nap, I'll adjust to bedtime the next evening. So I hope everyone is paying careful attention to what Matt just said. I mean, that's an important list because I think one of the very common things is for people to just not get a great night's sleep.

And I think most people think, okay, I'll drink a little more caffeine, I will go to bed a little earlier tonight, maybe catching a nap in the afternoon, this kind of thing. And I would have thought that too, and maybe even suggested that. And if you listen to the first episode and where I list in a doomsday manner the things that can happen by way of a short night, you would think that that's what I would then recommend.

But it was really imprinted on me by a wonderful sleep clinician, Michael Perlis, who sort of described some of these features and exactly the reasons sort of underlying them. And I think I've just tried to bake that out into a formula that makes sense. Again, it's not about the rule, it's about explaining it, because when you explain it, at first, it sounds contradictory and paradoxical.

When you understand it, it hopefully sounds logical and actionable. So that would be the first suggestion. - Could I just, sorry to interrupt again. My audience hates when I interrupt, but I'm doing it on their behalf. - Oh, I love it. - Because I like to think that there's some value in some of at least what you say in response.

I saw a really terrific post from Dr. Rhonda Patrick, who we both know and admire for her public education or public health education work. And she described a study whereby if people are, I think it was slightly sleep deprived, maybe by a few hours, that some of the disruption to morning blood glucose regulation that is known to accompany partial sleep deprivation and certainly complete sleep deprivation, but in this case, partial sleep deprivation could be offset by still exercising in the morning.

- That's right. - Which, frankly, I have to say, if I haven't slept that well, then normally I'm like, maybe today's the day I don't exercise. But now having heard that information, I make it a point to still exercise, sometimes with a little bit less intensity, because I don't want to be completely exhausted in the afternoon and go to sleep at 4 p.m.

or something, really disrupt my schedule. But I thought that was really interesting because it's a sort of partial inoculation of the blood glucose disruption caused by sleep deprivation. - I'm so glad you brought it up. It's a fantastic study, and Rhonda and I, I think even tried to discuss it some years ago on a show, but I like it because it does offer some degree of actionable hope and a strategy.

Blood sugar, absolutely critical. It is very sensitive to sleep. When you don't get enough, it goes in bad directions. You used a very specific word, cleverly so, and that word was partially. At first you hear or read that study, and Rhonda was never suggesting this too, I'm not saying that.

You think, well, if it offsets blood sugar, and the study was saying exercise can nullify a lack of sleep, you conflate that single outcome benefit with the idea that, well, but maybe it doesn't actually, does it compensate for the deficits in immune function, or cardiovascular disease concerns, or my hormonal health, or my learning and memory, or my emotional and brain health.

Maybe it does, but maybe it doesn't. So I think I would always just caution people to saying, when you hear a study like that, it's very natural to think, oh, that must mean that it translates to everything else in my body, and everything else in my brain. It may, but it also may not be.

- Terrific, so if you don't sleep that well, do your best to still get some exercise, but just be mindful of the fact that, in the winter months, especially, that might, if you go too hard in the gym or on a run, you might be a little bit immune compromised, just be mindful of the fact that you're a more vulnerable being when you're sleep deprived, but that exercise can help adjust things in the right direction.

And if it's early in the day, presumably that's not going to disrupt the proper bedtime. And if it's later in the day, I suppose, as long as you don't need caffeine in order to do that exercise, and/or if you're familiar with exercising later in the day, fine, I find if I exercise, I'm not one of these people that can go for a run, seven o'clock at night, and then just shower and go to sleep.

- Of course, because you're a morning type. - Because I'm a morning type, other people can. Okay, we'll get into exercise a bit more in a later episode. - We should do, yep. - We'll be sure to do that, but nonetheless, just raise that now. So what are some of the other unconventional protocols for sleep?

- So I think other suggestions I would have after do nothing would be, try to think about limiting your time in bed. If you are struggling with sleep, this is something that is used in probably the most well-validated psychological intervention for insomnia, and it's called Cognitive Behavioral Therapy for Insomnia, or CBTI for short.

What happens is that you work with a clinician, they interview you, they assess all of the reasons that you may not be sleeping, and then they create, from their toolbox of many different options, a bespoke, tailored sort of Savile Row soup prescription for you for your treatment. If you look at the studies of that collection of different tools in the CBTI box for intervention of insomnia, and you ask of all of those, which seems to carry the greatest impact on insomnia, which has the greatest sort of gravitas, it seems to be this thing that we call Bedtime Rescheduling.

It used to be known as Sleep Restriction Therapy, but obviously, if you come to me and you say, "Look, I am not sleeping very well. "I've got insomnia." I say, "I understand, and I've got a treatment for you. "It's called Sleep Restriction Therapy." And you say, "No, no, no, you didn't understand.

"I'm not getting enough sleep." But it's not quite that. Here's how it works. If you are spending so much time in bed, too much time in bed, you are not forcing your brain to be efficient. And by way of constraining your sleep window, even to, let's say, five hours a night to begin with, I brute force ruthless efficiency from your sleeping brain after several days.

So another analogy would be, let's say you're trying to make a nice thin crust of pizza base, and you put the dough on the table, and you start rolling it out. If you roll it too thin, it starts to get gaps and holes in it. Why? Because you've spread it out too far, and you've started to create these absences.

That's the same thing that happens. And it's very natural. As an insomnia patient, you would say, "I'm just not getting enough sleep, "so I'm going to start spending more time in bed." It's the very worst idea. Another way would be to say, "Look, I go to the gym, "and I spend about an hour and a half working out." But if I were to videotape you, a lot of people are doing the, I think I've coined it as your phrase, but the 11th rep, where people do the 10 reps, and then all of a sudden there's the selfie, or there's the social media.

- Oh, yeah, the texting. They finish the last rep, put it down, and then immediately to their phone. - And if you look, they're only working out for about, let's say, 45 minutes, and the other is wasted. So what if the next day you came to the gym, and I said, "Look, I'm sorry," and there's some big bouncer guys at the door, "You are only allowed to work out for 40 minutes, "and then we're going to eject you." And the first day, you go back and you do the same thing.

And then you've only got through 30% of your workout. So you get booted. The next day, you come back and you do a little bit more, and you get booted again. After about five or six days, you've built up such a strong desire and hunger to get your workout in.

You walk in, you put your phone on silent, you put it over in the corner, and you just get to it. And that's the same thing that we're trying to do with sleep restriction therapy. So you have to be a little bit careful, do it under supervision, especially if you're driving or you're operating, heavy machinery.

We just want to keep an eye. It's not necessarily a big concern, but we would say, "Okay, Andrew, "you're currently spending almost total "about eight-ish or seven and a half hours in bed. "Tonight, I'm going to restrict you down "to five hours a night, "and we're going to do this for the next week." And the way that we normally do it is I don't change your wake up time.

I change your to bed time. Why? It's easier to stay awake longer than it is to wake up earlier. So I put it on the front end of the compromise, and at first, things don't change. But after maybe about four or five days of going through this, I build up enough of a short-term debt in your system that your system all of a sudden thinks, "Gosh, I just cannot be as lazy anymore.

"I can't do this thing of waking up "in the middle of the night "and spending an hour and a half awake. "I don't have the choice anymore." There's so much physiological buildup and pressure to do this. And gradually, what happens is that you sleep longer. You don't wake up as much.

And after maybe about two weeks of doing this, all of a sudden, you go to bed at this later time. So for you, let's say you normally go to bed at eight. I'm going to have you go to bed at maybe 10, 30, 11, but we're still going to have you wake up at that sort of 4.30 a.m.

mark that you would normally wake up. And all of a sudden, you go to bed at 10, 30, 11, you're out like a light. And then again, the next thing you remember is your alarm going off saying, "I'm sorry, you've got to wake up." And what happens by way of that reset is gradually we will then, once you're stable, we will start to back it off.

We'll start to have you go to bed at 10. And if it stays stable, then 9.45, then 9.30, and titrate you back to where you were. And if there's any sign that you're starting to not sleep well, we zip it back up again. The goal here is, in some ways, almost like hitting the reset button on your Wi-Fi router.

I'm trying to retrain your brain to better sleep because when you are not sleeping well, you've lost your confidence in your ability to sleep. And when I do this technique with you, gradually your system and you cognitively relearn that you are a good sleeper and you can trust in sleep.

And now your sleep does not control you. You control your sleep. The hard part, however, is that it's not easy to go through. And we have to be, we have to usually ask two questions with individuals. Firstly, what is your motivation for better sleep? We need to know that you really are motivated.

And then second, you just stay with a high touch white glove frequency, checking in on individuals and motivating them to keep going 'cause it's very easy to fall off the wagon. So that's the next suggestion, sleep restriction therapy or bedtime rescheduling, as we would call it. - You said it's difficult for people to go through.

You know, it takes a little bit of rigor, a little bit of attention, means in some cases getting less sleep than one would like. But as compared to something that, you know, sadly I've experienced a lot in my life of having challenges with sleep and trying to get things back in order and looking at the bed and just going, "Oh my God, battleground," you know, battleground.

You know, it's, I think it makes a lot of sense. And I love the analogy to the gym. Somehow, if there's a restriction to one hour in and out the door, or maybe 70 minutes in and out the door 'cause you need to put your stuff in a locker or something like that, it always, at least for me, gets done best when you just have those constraints.

I think there's something about the human brain that we don't do well in unrestrained systems that I really think guardrails are fantastic. I love deadlines, for instance. - Yeah, discipline is essentially the-- - Yeah, hard deadlines. Like, or as they say in academia, 'cause we, you know, write grants all the time, drop deadlines, which who made up that term?

But like, if you don't make it, that's it. It's like, there isn't a, "Hey, I'll send this in tomorrow." 5 p.m. Pacific time, that website closes and you better have you-- - Boy, do you get things done all of a sudden. It's surprising how much distraction you can, you know, pull out the noise and focus on the signal.

It's great signal to noise ratio. - Yeah, and I love the idea that one can control their sleep as opposed to sleep controlling them. I think that that's, and this notion of sleep confidence, one's confidence in their ability to sleep. These are important terms and they're more than just terms because I think that a field and an area of health practice and gosh, what's more important than sleep?

It's the foundation of mental health, physical health and performance, period. Really thrives on a common nomenclature. And I really appreciate that you're, you know, peppering these episodes with new nomenclature that captures a lot of the essence of the protocols and the mechanisms. So there, that's my editorial, please continue.

- I would say that in terms of other things, maybe just to go through them a little more quickly, we've spoken some about a wind down routine. Most people under-appreciate the importance of a wind down routine. We often think that sleep is like a light bulb, that we dive into bed, we switch off the light bulb and sleep should appear just as quickly.

It's untrue. Sleep in terms of a process is much more physiologically like trying to land a plane. It just takes time to come down onto the terra firma of good sleep at night. Whatever it is you enjoy as a relaxation method, engage in it, could be listening to a podcast, could be reading a book.

Maybe it's a meditation, it's light stretching. Maybe, whatever it is that you do, just build it in to your regimen. You know, you would never, you know, be driving down the road and then pull into your garage at the same 40 mile an hour speed. You gradually decelerate and you come to a stop.

It's the same thing with sleep. So you need to find some way to decelerate and we've spoken about methods already as to how to do that. The next tip is a little quirky and funny. Do not count sheep. There's a great study from my colleague, Dr. Alison Harvey at UC Berkeley, and she put this to the test.

Didn't make people fall asleep faster. It made them take longer to fall asleep. However, she did find an alternative. If you are not into meditation or podcasts or sleep stories or whatever it is that you wish for, try taking yourself on a mental walk. And it has to be a walk that you know very well.

So let's say that you walk your dog every day and you know there's a couple of walks that you take with your dog. Do it in hyper detail. So close your eyes, you go to the front door, you clip in the dog to the leash, you walk out, you go down the steps, out to the driveway, then you take a right, but you always cross over and you look to the left and the right 'cause that's the place where traffic always comes.

You cross over and now you're walking up and there's that strange sort of set of garbage that's been outside of that house for a long time and you don't know why it hasn't been cleared. And then you move. That type of high fidelity detail allows you to do what we said earlier, which is get your mind off itself.

And when you do that, again, typically you fall asleep faster and that's what she found. It was a great, great study. I really enjoyed that. - I'm curious as to why it works so well. And I'm not challenging that it works. I can imagine having just closed my eyes and kind of imagine what that would be like.

It's very pleasant. There might be, and here I'm just speculating, something about engaging one's procedural memory because that's procedural memory. You're trying to remember how you do something as opposed to declarative memory, which is about facts. I remember this and this is gonna happen tomorrow. I wonder whether or not there's something about using a procedural memory as opposed to a declarative memory visualization.

Somebody should do that study. - They should. And I think it's certainly possible that when you're incorporating some aspect, some aspects of the scene and the information is more sort of veridical and maybe sort of episodic declarative memory. But when you're taking yourself for a mental walk, what is the fundamental premise of that?

It's a walk, it's motion, it's procedural memory. And so maybe it's something to do about with being more attentive to becoming embodied because when you're out walking and you're moving, it is a more embodied experience than just sitting there at your desk, which is mostly your head and very little your body.

So I think it's an intriguing idea. And I think another tip that I now think of, which also comes from the work of Dr. Alison Harvey, when individuals come up to me after sort of public events or they see me at the airport, they'll say, look, every night for some strange reason at 2.45 a.m.

I wake up and it happens three or four nights a week, my first question to them is, how do you know it's 2.45? And they say, well, I look at the clock or I look at my phone. Best piece of advice next, remove all clock faces from the bedroom.

No matter how bad your sleep is going to be that night, knowing what time it is, is only going to make matters worse. It is not going to make matters any better. And that can create an anxiety trigger that you think it's 2.45 and then you're tossing and turning, you look back at the clock and now it's 3.14 a.m.

And you think I've got to be awake at six, I've got a big meeting and now it's 5.25. Don't do that to yourself. And I, even though I don't typically struggle with sleep, I have no clock faces in my bedroom. The phone that I use to help do the guided meditation is an old phone and it has only wifi connectivity and nothing else on it.

And I will only hit play and then I will never turn it around. I will not look at the clock face, just doesn't help me. - Another incentive for keeping the phone out of the room, if one can, I understand there are reasons when one would want the phone in the room if it's potentially signaling an emergency.

- I think it's a very important point and we've done some work in this area too. What that phone does is create a low level of anxiety. It's what we call anticipatory anxiety. One of the mechanisms separate from that, well, it's related to that. If you look at teen phone use, one of the reasons that they don't sleep very well at night is that they're constantly checking their phones because of FOMO, a fear of missing out.

What has gone on as I've been asleep? And it's stunning the data, but for most adults, the other reason I don't like advocating for phone use, when your alarm goes off in the morning, what is the first thing that you do as you're in bed? You swipe right or you unlock your phone and you instantly start checking social media, emails, text messages.

And this tsunami of stress and anxiety just floods over you. It hits you like this wall of anxiety. And I bring this up because it again, trains your brain for expectation of that. Anticipatory anxiety has a consequence on your sleep. And everyone knows this. Let's say that you've booked an early morning flight and you've got to wake up at 5 a.m.

when normally you wake up at 7 a.m. Two things will usually happen. First, you know that you're just not going to sleep as deeply that night because you're on edge. And this is for an interview or it's for a critical, this is a non-negotiable trip that has to happen.

You've got to wake up. The second thing is that when you are expecting that wave of sort of a need to wake up and maybe it's just, I'm expecting the phone again, you will wake up just a few minutes before your alarm. It's stunning how many people will say, I had this big flight the next day.

And you almost know I'm going to wake up two minutes before my alarm goes off. Why? Because your brain has stayed in the shallow state of anticipatory anxiety and you don't get as much deep sleep. And we've now demonstrated that we know this. When you have that low level of anxiety, the depth of your deep sleep is not as deep.

You don't get the good. So again, not to be trying to dictate what people do, just be aware that when you do create that behavior and that regiment, it becomes almost like a knee jerk sort of trained habitual response. - Terrific. Let's talk about some of the advanced tools for sleep enhancement.

You know, what sorts of methods could one incorporate? You know, what are some of the data? And is there any way that we can sort of lump these into sort of some framework or categories? Because I know there are a lot of different tools. - There are. And I suppose this would be, you know, I know our friend Petra Teer has spoken about medicine 3.0.

I think this would probably be sleep optimization 3.0. What is coming down the pike? What is in the research? And I think, you know, could make it to market or has made it to market, but yet we're still right on the cusp. We've seen, we again in the Royal We, have been able to augment human sleep in at least four different ways.

There are methods for electrical brain stimulation. There are methods for acoustic stimulation of sleep. So electrical stimulation of sleep, acoustic stimulation of sleep, thermal manipulation of sleep, and then finally kinesthetic manipulation of sleep, meaning movement-based stimulation. And maybe I can just sort of go into each one of those.

The electrical stimulation is probably the most well-rendered of all of those four. In part, because we started there and here it's not the Royal We, we have done a lot of work on this. And I can tell you a little bit about a company emerging from that. But when you're trying to manipulate the human brain, the principal currency in which the brain communicates is electricity.

Now, there are lots of things that help it do that, such as chemicals, but the principal language and verbiage of the brain is electricity. So if you're going to manipulate the brain, why don't you speak in its currency of electricity? So we and others have developed a method based on something called direct current brain stimulation, and specifically something called transcranial direct current stimulation.

And I'll unpack that. Trans meaning movement, so if you've heard of transport, it's about moving things from one port to another. Transatlantic, moving, you know, across the Atlantic. So here, the start of it is moving. You're moving something from one place to the next. Transcranial means through your skull.

So we're moving something through your skull. Transcranial direct current is the type of voltage or the type of electrical impulse that we're putting in. It could be alternating current, or it could be direct current. And early methods and those we use have been direct current. So transcranial direct current, and then stimulation.

We're trying to stimulate the brain, specifically the cortex. And the way that we do this is that we apply electrode pads to your head, and we insert a small amount of voltage into your brain. Now, it's so small that you typically don't feel it, but it has a measurable impact on that electrical brain activity.

So very early on, scientists, and we weren't the first to do this by any means, there was a great paper, now a famous paper in my field, by a wonderful scientist, Jan Born in Germany. And they took a group of subjects, and they applied these electrode pads specifically to the front of the brain.

And I'll explain why we target the front of the brain with sleep electrical enhancement, or the electroceutical, as it were. They applied these electrode pads to two groups of participants, and then they let them go into sleep. And as you'll remember, we described that in the first two or three hours of sleep is when you get most of your deep sleep.

And they were targeting those deep, slow brain waves that we spoke about, those big, slow, powerful waves that define deep sleep. And what they did in one of those groups, the other group was the placebo group, they still had the electrodes applied, they still went to sleep. In the stimulation group, they waited until those individuals went into deep sleep.

And I told you in the first episode that those deep sleep brain waves were going up and down very, very slowly, maybe just once or twice a second. So they started to stimulate the brain, inputting these stimulation pulses at a very slow rhythm, trying to match the rhythm of the brain.

In fact, they were less than one hertz, less than one cycle per second in terms of a pulse. It's almost as though we're trying to act like a choir to a flagging lead vocalist. And as these brain waves are going up and down, you're trying to sing in time with those deep sleep brain waves.

And in doing so, you're trying to boost and amplify the size of those deep sleep brain waves. Now, to begin with, they just waited until they went into deep sleep and they started to stimulate at that frequency. And I'll come back to why that's important in a second. But sure enough, what they demonstrated, they were able to boost the electrical quality of that deep sleep by about 60%.

And they were also able to almost double the amount of memory benefit that sleep provided, which is very impressive. That is impressive. Now, I should note that there was more recently a replication attempt of that paper, and they did a very good job. They really did it to the letter.

And they weren't able to replicate the effects as powerfully. However, subsequent studies have now taken a more nuanced approach, and it's the one that we've taken too. And it's called closed loop stimulation. Closed loop here simply means that I'm not going to just wait until you go into deep sleep, and then just take a chance and start stimulating your brain, not knowing of the synchrony of my pulses into your brain relative to the brain waves that you're experiencing.

Closed loop does do that. So what I'm doing is I'm measuring the electrical brain waves that are occurring. And because they're nice and slow, they're very predictable. And I can program my algorithm and my brain stimulation machine to say I'm going to wait and wait. And as soon as you are on this peak of your slow wave, which turns out to be the negative trough, but I'll forego that, we then try to strike at that point of midnight when you're going through the biggest sort of powerful dip in the brain wave.

And we're trying to sort of enhance it, same with the peak. So this is where we get a stimulus from the brain, your electrical brain activity, and then we create a timed response. So it's a stimulus response. It's a call and response loop. And by way of doing that, it's a much smarter specific method than a more generalized, I'm just going to stimulate and hope I catch those waves at the peaks.

The reason is important because different people have different speeds of their slow brain waves. They're all slow, but your speed of brain wave may be a little bit different to mine. And if I'm off with my stimulation by let's say just half a second or a quarter of a second, time and time again, I may be leaving some benefit on the table.

But closed loops stimulation creates this personalized electrical prescription of stimulation. And when you do that, you get very reliable benefits. You can boost those deep slow brain waves. You get the memory benefits, but also what we found is you not only boost those deep sleep brain waves, you boost another electrical signature that I spoke about in the first episode called sleep spindles.

And it seems to be the combination of those two things by way of electrical stimulation that provides the benefits. Now, I should note, I haven't mentioned this before, you can buy these devices on the internet DIY style. Do not do that. If you go onto the internet too, you can also find some horror stories.

People have misappropriated the voltage. They've got skin burns, they've lost their eyesight for several weeks. Do not do this at home. I promise you, use, you know, wait until these products come out. And that's one of the reasons why we've scaled into a company and we're trying to do this.

We've got a long way to go yet. Huge number of trials that we have to do before, you know, I feel ready to really lay it on the table and say, "You should absolutely buy this. It's well worth it." But we're getting very, very close, I would say. Great.

What about thermal manipulations, temperature? I mean, there's such a tight relationship between temperature and sleep and wakefulness for that matter. What sort of technologies, tools, protocols exist that use thermal manipulation as a way to augment sleep? I love this topic because there are high-fi, low-fi and no-fi technologies that you can use.

The story of sleep and temperature, as you mentioned before and reiterated, in terms of the three-part stanza, that terse that I would describe is, again, you need to warm up to cool down to fall asleep. You need to stay cool to stay asleep. You need to warm up to wake up.

What that refers to technically in sleep science are what we call the thermal trigger zones. So, warming up to cool down to fall asleep is what we call the sleep onset thermal trigger zone. Cooling down or staying cool to stay asleep is about the deep sleep trigger zone. And then warming up to wake up is the activating alertness trigger zone.

Studies, if you looked at them to begin with before they manipulated that, found something fascinating. If I take you, Andrew Huberman, and I bring you into my lab and I remove your phone or your laptop and you say goodbye to your friends and family and I bring you into the center and there are no cues as to what time of day, no windows, no nothing.

And I'm just going to say, "Look, I'll keep asking you, but at the moment that you feel most sleepy, just let me know." It turns out that before that we'd done the delightful intervention of inserting a rectal probe into you because that's the best way that we can measure your core body temperature.

So, we're measuring your core body temperature and sure enough, despite you knowing nothing about what time it is, the moment that you will tell me, "I am ready to go to bed and I am sleepy," is the moment when you are on the greatest decelerating trajectory of your core body temperature.

It is highly predictive of how sleepy you will feel. The way that your body does this is by pushing blood out to the surface regions of your skin, notably your hands and your feet, because these are these highly vascular regions. And you had a great podcast from one of my heroes and good friend, Craig Heller, who's done some amazing work on this at Stanford.

So, naturally, as we lie down, blood races to our hands and our feet and also our head, and we start to release that heat trapped in the core of our body. And by releasing that heat at the surface, our core body temperature drops. Hence, the outer surfaces of you, hands, feet and face, have to warm up for your core to cool down for you to fall asleep.

And in fact, there was a great nature paper some years ago, they just measured the temperature of someone's feet and they looked at how quickly they fell asleep and when they fell asleep. Sure enough, the warmer your feet, the faster you fell asleep. Why? Because the warmness reflects the blood dilation and the pumping out of the blood to the periphery.

And then they did it in rats, where they started to warm the paws of the rats and the rats fell asleep more quickly. I love this notion of, again, we don't do anamorphic, but I love the notion of wrapping a beautiful little rat up in cotton wool and I'm warming its feet with this pad and it's just blissed out and then, poof, he's gone, after all, she, I respect their privacy.

So, that was the early evidence. That then led to a series of manipulation studies. The most notable is brilliant. It comes from a colleague in the Netherlands, Ousmane Semmeren and his group. They created essentially what was a wet, think about a wetsuit. But that wetsuit is covered with all of these thin tubes, almost like veins that go all over the suit to all territories of your body.

And then what they would be able to do is perfuse water, warm water or hot water, exquisitely to different parts of the brain or the body. - Cool. - Amazing. Yeah, no pun intended. So, what they did was then they started to manipulate these peripheral regions. And sure enough, when they did this, they were able to have individuals fall asleep 25% faster.

And these were healthy individuals who are normally sleeping within a very natural quick period of time. But they were able to lop off 25% of that time simply by warming these certain parts of the brain to lift the blood away from the core of the body. And by doing that, they accelerated the temperature core deceleration and therefore increased or accelerated the speed with which sleep arrived to those individuals.

Sleep appeared with much greater alacrity than it would have done otherwise, even though it was quick anyway. So, them not being satisfied with that, they moved on to the deep sleep trigger zone. And this isn't, you need to stay cool to stay asleep. And here now, they started to just continue to cool the core, the central aspects of the body.

What they were able to do is increase the amount of deep sleep by somewhere between 25 to, look at some of the data, almost 40 minutes they were able to boost the amount of deep sleep with the thermal manipulation. And when they were measuring the electrical brainwaves and they decomposed those brainwaves, even the power and the electrical quality of those slow waves was increased.

Very impressive too. Next, not being satisfied with that, they turned to older adults for the reasons that we've just described. What they found was that in those older adults when they were not manipulated with this thermal temperature, in the second half of the night, there was a 50% probability that they were going to be awake for some part of the second half of the night.

When they did the thermal manipulation, they dropped that number down to 5%. So they reduced a 50% probability of waking up down to 5% in older adults. And again, they improved the quality of their deep sleep. Think about, by the way, why that was so effective for older adults.

I guarantee you, you've probably seen, you've been in a warm climate or you've been down on the beach, you know, here sort of in Los Angeles, and people are out in shorts and t-shirts or crop tops. And then occasionally there will be someone, and I've seen these sites where, you know, a child is sort of wheeling along their elderly parents, a beautiful sort of scene of caring.

But the older adult, they're not dressed in the same way that everyone else is dressed on the beach. They are wrapped up, some of them have a woolen hat on. Why? Older adults cannot thermoregulate anywhere near as well as young adults. Is that right? And it's the reason that older adults will always be saying, "I'm just so cold and my hands and my feet especially are always cold." Now, that's a problem for sleep, because if you cannot vasodilate at the level of your hands and your feet, you can't get the blood out from the core, you can't drop your core body temperature as much.

And we started to understand from those types of data that part of the aging sleep-related problem equation is not just that the brain deteriorates in sleep-related regions, which we've been doing most of our work on, it's also part of a body equation and a thermoregulatory equation. There was also a great study unrelated from Australia.

They looked at insomnia patients, and they put their hands or their feet in warm water. And by doing that, it's a manipulation. And you can see how quickly their hands and their feet, what we call vasodilate, fill with blood. Healthy people vasodilated very quickly in response to that warm water, meaning that their hands and their feet sort of had this red, or at least for my feet, they would be this red tone to them.

However, in the insomnia patients, they did not vasodilate anywhere near as well. So once again, it suggests that when you have problems with sleep, part of the equation may be that you have impaired thermoregulatory ability. And we do see this in insomnia patients. So that was, I think, a brilliant causal manipulation.

The problem is that most of us don't have access to a sort of come-to-bed-at-eyes thermal suit. So what can we do as a consequence? Please don't cut that. I get myself into terrible trouble, rightly so. -You'll be all right. -I should be punished. What they did then was to say, "Well, okay, let's look at this.

Is there something that we could do that's cheaper and more accessible to the general public?" And if you look, there's a literature that preceded that manipulation, and it's so reliable that we now have a term for it in sleep science. It's called the warm bath effect. And many people will say, "Look, I love to have a warm bath or a hot shower before bed, and I think when I get out, I'm nice and toasty, and it's because I'm nice and warm that I fall asleep and I stay asleep." It's the exact opposite.

When you get out of the warm bath or the shower, you have once again vasodilated at the surface of your skin. You get out of the bath, you get this huge thermal dump of heat away from the core. What happens? You fall asleep and you stay asleep more soundly.

Now, there are other reasons that that has a benefit. It's relaxing, you decompress, you're staying away from technology, etc. But that is one of the thermal benefits. And in fact, there were studies by a legend in my field who passed away just a few years ago, Jim Horn at Loughborough University in the UK.

And they did some of these pioneering studies. They were able to improve the amount of deep sleep by almost 40 minutes in some individuals. What was the protocol there? As I recall, I think they were in the bath for somewhere around... The bath duration time was somewhere around 30 minutes, but they were doing sort of segments where it was maybe 40 minutes, 10 minutes in and then you could sort of get out.

I think the temperature, because it was UK, was around about 40 degrees Celsius somewhere in that region. I may be getting those numbers wrong because I know we like to protocolize some of this. But they were able to show some really pleasant benefits to deep sleep. It also helped people fall asleep, helped them fall asleep by about 25 minutes faster in those people who were really having a hard time with sleep.

I'm going to take a hot bath tonight. I sometimes do the sauna in the evening before sleep. I'm a big fan of cold in the morning, cold shower, cold plunge in the morning. Because you're reverse engineering the equation. You're trapping the heat into the core of your body, you're waking yourself up.

Right. And then in the evening, I've used sauna. The one issue with sauna is I really crank the heat of the sauna. And then sometimes if you do that right before bed, you take a warm shower right afterwards, you get into bed. Oftentimes, I'll wake up thirsty because it dehydrates you.

And then if I drink a lot of water to hydrate after I'm in the sauna, then I'm waking up too much in the middle of the night. So I think sauna is great, but right before bed... I would love to... I don't have a sauna at home or an access to...

I mean, there are saunas in and around where I live. But what I want to do is have it proximal to my bedtime. And my bedtime, because I'm a neutral type, you know, sort of around 11-ish, nowhere is open and willing to allow me to sit in the sauna.

How long do you sit in there usually? I'm a little bonkers about this. Well, if it's in the evening and I just want to relax, I would say maybe 20, 30 minutes. And I tend to go really warm, warmer than I want to stay here. What does Peter do?

Peter, is he your friend? I've done sauna cold plunge with Peter. He usually does it in the evening, goes sauna cold, sauna cold, sauna cold. Okay. Warm shower. And I don't know how many nights a week he's doing that. But in terms of the temperature of the sauna, you know, generally somewhere between 175 and 210 degrees, depending on how heat adapted you are.

But I think a hot bath is great or a nice hot shower. Yeah, I've certainly done that. And when I'm traveling with jet lag, I will absolutely... That's part of my sort of jet lag protocol. I'll make sure I do... 'Cause I don't really struggle too much with sleep, at least at present.

But when I go through jet lag and I go back home to London, of course it's tough. The worst. Protocolize the living daylights out of that and do as much as I can. So I think that's probably the end of the thermal story. Although we are now trying to see if we can take low fire approaches where we're going to do some foot warming.

We're trying to develop some foot warming technology that can be built into maybe a mattress. And some mattress companies, there are some great ones. I know, obviously, Matteo at Eight Sleep, and they are doing amazing things. I think his company, again, I have no affiliation, but we connect very well and he's brilliant.

So they're doing something like that. I do use and love my Eight Sleep. Here's what I'd love somebody to engineer. And we've got a lot of people who listen to the podcast who think about product development. It would be wonderful to have a portable pair of socks so that you can use them when you travel or when you go to sleep anywhere at home or elsewhere that would warm your feet up at the beginning of the night.

So this is a place for us to recap. Warm up to cool down, to fall asleep, right? Stay cool, stay cool. To stay asleep and then warm up in the morning to wake up. And so that is pretty straightforward to build into a pair of socks. Somebody can do this, somebody do this.

Okay. - So we've done electrical, we've done thermal. - What about auditory? - Auditory, so acoustic stimulation. In a very similar way to electrical stimulation where you're trying to target that deep sleep and see if you, a better analogy is probably a metronome. And you're trying to see if you can kind of force the metronome further over back and forth with these types of technologies.

So auditory stimulation came on the map. Again, I think probably Jan Born's group in Germany was some of the first to do this. They initially started with the same generalized approach where they would take acoustic tones and they would first assess what is your level of awakening threshold? So you'd be asleep and they would just have these tones, very light tones, like a sort of a ping, ping.

And they would gradually increase the volume up and they would look to see what is the point where that volume of the tone wakes you up. And then they understood your specific threshold, what's called an awakening threshold. And they would set the volume to a sub-awakening threshold. Great, so you've got that locked in place.

And now you start, and they did this within the first 90 minutes of people falling asleep. They started to play these sub-awakening level, volume levels of tones, but they were playing them at this very slow frequency as if again, they're trying to sync and match the slow dancing rhythm of the slow brainwaves.

And sure enough in that first study, and it was indiscriminate, meaning they just set the tones, playing like a metronome, set the tone, set the, and then, sorry, set the volume and then set the cadence of the volume, the speed, the frequency of those tones to just a little bit less than one hertz, a little bit less than one cycle per second.

And then off you drifted to sleep and they played it for the first 90 minutes 'cause that's the rich phase of deep sleep. And they were able to increase the amount of deep sleep significantly. The problem in that first study was that they also did a memory test because in all of these studies, including my own, even if I boost your sleep tonight, Andrew Huberman, my next, if that's the result that you show me, I have four words for you as a scientist.

Yes, and so what? (laughs) Is it functional? Because if I boost your sleep, but it doesn't change anything to you, the organism the next day, I'm going to suggest that that enhancement is epiphenomenal, not functional. - So it has to improve some reasonable metric in wakefulness that like improved memory, improved task switching ability.

- So it's outcome measures. - Grip strength. - Correct. - Something. - Yeah, so even if I, for example, lower your blood pressure with a new drug, if I'm not changing your cardiovascular disease risk, then the question is, why am I just continuing on with the drug if it's not really changing much?

Same thing here. And what they found was that when they did the memory test the next morning, by enhancing that deep sleep, there actually wasn't a memory benefit. So perhaps what was happening is that this was just non-specific. So again, they then returned, and now others have returned to the closed loop mechanism, where now I've got electrodes on your head and I'm measuring your slow wave brainwaves.

And literally I am next door in the room and I'm watching those slow brainwaves go up and down. And then I've got a computer algorithm that is watching those, "watching" in quotes, watching that too. And it's predicting when the next wave is going to come. And when it does, auditory tone clicks, sub-awakening, you don't wake up.

And sure enough, when you sort of tone into the brain at that time, you boost the size of that brainwave. And once again, they boosted the size of those deep sleep brainwaves. They also improve those more quick bursts of activity, the sleep spindles. And now sure enough, they were able to improve memory.

However, if you look at that paper, and here's why I think the first method may not have worked very well, and why I don't suggest people start trying to set this up themselves. When they kept stimulating the brain, slow wave after slow wave, after about three or four strikes of the metronome to boost those slow waves, the benefits stopped.

And if they kept going, you started to inhibit the amount of naturally occurring deep sleep brainwaves. Why would it do this? Deep sleep brainwaves, I told you in the first episode, are a act of incredible neural coordination. It's mass coordination. Now, one of the extreme versions of mass coordinated propagated activity that is maladaptive, that is pathological, is called an epileptic seizure.

And your brain has in place for the most part, stop gaps to prevent that type of spread of vast amounts of coordinated, spontaneous electrical oscillations, because the brain is such a conductive device that once you get it going, you've got to be careful, because it may start to conduct out of control.

So we think that these checks and balances that were in place, even though you can artificially stimulate it for a while, after a while, the brain says, "You've got to back off for a while because this is getting a little bit out of control." You do a breath pause, and then you restart again, and you get the benefit, and then you breath pause.

So you've got to do it a little bit intimately. Now, you've got to read the, what we call the supplemental materials of that paper. You've got to go, it's like the fine print on a legal document. If you dig into it, you can see that that was the case, but it wasn't necessarily evident.

So those were really the data on acoustic stimulation. And now with this closed loop acoustic stimulation that we've got going on, it seems to provide these nice benefits. Some people then will probably be asking, what about these noise machines? What about white noise, et cetera? I've taken a look at this, and so far, I think for white noise machines, the data is equivocal.

There was a recent study, a review article, I think it looked at about 37 different studies. I could have this wrong. And what they found was that there was no reliable, robust directional effect of white noise machines on sleep. Some studies demonstrated that it helped sleep. Some studies didn't change sleep.

Some studies suggested it may make sleep a little bit worse, just nothing reliable. - But maybe it's masking external sound. - Correct, so I think if, and one of the positive studies in that scenario was a study that was done in New York City. And it was in a region where there was a lot of external sound pollution and noise.

As you could well imagine, it's New York City. And sure enough, that's where they got some really nice benefits of the white noise machine. So I think it is, you're right, context dependent. There was an interesting recent study that came out from Eterman Lerner's group at the University of Texas, San Antonio.

And they didn't use white noise, they used pink noise. Now, what's the difference? Pink noise has a little less what we call power or intensity in the higher frequency ranges of the sound spectrum. And it's more enriched in the slower domain of that power spectrum, which you could argue is a bit more fitting with sleep.

And I think this study may have been a nap study or I may be wrong, but anyway, what they found was that they increased total sleep time by, I think it was close to 30 minutes with the pink noise. They did not change the amount of deep sleep, but they did enhance the amount of stage two non-REM sleep, which we have spoken about before and we will in subsequent episodes that is beneficial for things like learning and memory, including motor skills.

And they increased the amount of REM sleep to a much more modest degree, but those changes were significant. So I'm not trying to rule out noise machines right now and I have no affiliation with any company or anything in that space. I don't want to throw the baby out with the bath water.

I just simply think that right now that we don't have enough evidence, but as you and I know, as scientists, absence of evidence is not evidence of absence. Just because it doesn't exist, doesn't mean that I don't think that it's still a potential route, these types of machines. - What about kinesthetic, stipular tools, protocols?

Body position is something that has an interesting relationship to propensity to fall asleep based on brain cooling that we talked about in another episode, but what about manipulation of the body's movement? Is there anything in that domain? - It sounds wacky at first. - Yeah, it does, but I said it, so I still want to know.

- Come on, social media, just be nice, be friendly. I would say that if you look back in, again, the annals of human history, from the very early inception, you will see mentions of a child being rocked in a manger or rocked in a crib. Often parents will take their young infant and you will quote unquote rock them to sleep.

And we as adults will sometimes get in a hammock and if you're rocked, what happens? You will fall asleep. It's that prototypical image of someone with a hat over their face and in a hammock and they've sort of fallen asleep. So it was very clear that something was going on in this space.

And then a group from the University of Geneva led by another fantastic sleep scientist, Sophie Schwartz, did an epic study that, again, it's one of those studies that I probably once more wished I'd done. Here's what they did. They took a bed frame and then they suspended it on chains from the ceiling.

Now stick with me. I'm not going in that, you know, there's no hot candle wax being applied here. Don't worry, I'll keep it PG again. And then the next thing that they did was connect a rotating arm to that bed at the side of the bed. And that arm would start to simply just push the bed laterally from left to right, left to right.

And they started just swinging the bed in a very controlled manner. But here, and I should ask Sophie exactly why they made this choice. They were rotating the bed, not at this sort of around one Hertz, which is what we'd done with electrical stimulation or acoustic stimulation. They were doing it at 0.25 Hertz, which is much slower still.

- Almost imperceptibly. - The bed is rocking, you know, once every four seconds. It's a very slow lull. And sure enough, what they found in the first series of studies, they did a nap study, a 90 minute nap study. When you did this rocking motion versus when the bed was still, they increased the speed with which people fell asleep.

They boosted the amount of deep sleep and they boosted the amount of those sleep spindle oscillations that we described. Not satisfied, they then said, well, what happens across a night of sleep? They did it then across a night of sleep. They replicated the same findings and now they got a memory benefit.

Now the memory benefit you could argue is modest. It was 10% of a memory improvement benefit when you woke up from sleep relative to the already sizable benefit that sleep naturally gives when you're not rocking the bed. But you think, well, 10%. If I were, let's say a student and I got a B and someone, the professor said, look, by the way, there is something that you can do and we can increase your grade by 10% and you can get to an A or an A plus depending on the grading system.

Would you take it? Would you take 10% benefit? Absolutely, you would. So grade point averaging increase. So it isn't trivial necessarily. - Well, I also, I'm positively surprised how important this but so what condition is for you sleep researchers. - Yeah, and so what? - You know, that enhancement in say deep sleep or rapid eye movement sleep needs to translate to some daytime benefit in order to really get you guys excited.

But here's why I think that's great. It's always great to have a high threshold for excitement. But one of the things that one could argue is that there are only so many tests that you can have in a laboratory of daytime functioning. I think I am on board the fact that sleep is the bedrock of mental health, physical health and performance.

So an improvement in, you know, a statistically significant improvement in deep sleep or REM sleep, to me just seems like that's gotta be good for something. We might not know what that something is to test in the laboratory, but it could be that the threshold for improvement of say gut microbiome production of neurotransmitters is, you know, 0.1% improvement in deep sleep.

We don't know, I made that up. So don't quote that statistic anyone. But I so admire the kind of extreme thresholds of what gets you guys excited. - No, your point is a very good one because you could argue based on what I just went back and said regarding the exercise study with Rhonda Patrick, I've just reversed my own threshold logic.

I said to you, well, okay, exercise was able to overcome some of the deficits that occur by way of sleep deprivation for your blood sugar. But don't assume that that necessarily means it overcomes the detriments, the other detriments that you'll have for your hormonal health, your thermoregulatory capacity, your cardiovascular disease, your brain function.

So I've just said, look, simply, you know, one thing doesn't mean that you've assessed all things. And now I'm saying, okay, if you don't show that it improved that one thing, then it's not functional. But Matt, by your own logic, you've said, but you didn't assess many of the other things.

So even if it didn't improve memory, as you said, the bedrock of all things health, you need to assess all of them before you make your conclusion of the yes and so what failed test. So you're absolutely right to point that out. So what was interesting after that data came out in humans, which is usually the opposite way around, they started to look in animal models and you mentioned the vestibular system, this ability for us to understand motion and movement.

And there's lots of mechanisms for that. They looked at mice and they started doing this rocking again and sure enough, the mice fell asleep faster. But then they found a strain of mice that did not have the lateral vestibular sensation mechanism and they rocked them just the same way, zero change in their sleep.

Because you could imagine, well, it's important to understand the mechanism here. Is it that when you're rocking, there is, it's not just about vestibular stimulation, maybe that rocking sort of modestly changes friction, which changes temperature. You could come up with all sorts of wacky reasons. This was a very clear causal manipulation of the lateral vestibular system.

And if that is not in place, you fail to get the benefit. So it clearly has something to do with the vestibular system. - Can I venture a guess as to why that is? - Yeah, please. - I interrupted, but in case I happen to be right by some chance, previously we talked about the need to lose a sense of one's posture and relationship to gravity in order to fall asleep.

But you have to go into this lack of proprioceptive awareness in order to fall asleep. Proprioception being the knowledge of where one's limbs are relative to the body and body relative to other surfaces in gravity. And this is something that can be accomplished in these, you know, flotation tanks and things like that and other ways go to outer space.

But- - The cheaper version. - The cheaper version. So could it be that the rocking at that very slow frequency is tapping into the vestibular system in a way that that proprioceptive feedback about body position is somehow starts to vanish? And because I'm intrigued by this idea that you have to lose perception of your body's positioning and proprioceptive awareness in order to fall asleep.

And maybe your description earlier of a protocol of going on a mental walk in order to fall asleep. I just feel like these things are starting to converge on some themes here. - On a central common pathway that could be the absence of proprioceptive. I think it's entirely possible.

In some ways right now, we think that these two things are associated that as you're falling asleep, gradually you will lose proprioceptive sensation. But simply the fact that two things are associated doesn't necessarily mean they're causal. But your suggestion here is a very elegant way of testing that hypothesis, which is that perhaps if you could show that the symmetric of proprioception becomes compromised when you start doing lateral sort of kinesthetic or movement stimulation, that's a very powerful demonstration that it's not just so here with the study in the mice, they lacked the lateral vestibular sensation and you lost the sleep benefit.

But maybe there's one step down, which is that when you lose that vestibular stimulation, you lose the benefit on the thing that really is augmenting the sleep, which is the change in proprioception. So this is the first step in a chain of command and you've missed the final common transactor of that ingredient called better sleep.

And those I would say are probably the four current bastions of sleep augmentation. Hopefully that describes to listeners the range of where sort of sleep 3.0, sleep enhancement 3.0 is going and also describes the way in which we can come down the strata from high friction, low friction to no friction.

And also in terms of cost where you can have high cost, minimal cost, low cost. I mean, hot bath or a shower is pennies on the dollars so. - Especially if you take a cold shower in the morning and save on your heating bill. So you can take a little bit longer hot shower in the evening and then you net to zero difference.

It's just my way of saying, take a cold shower in the morning. Feels great when you get out. What about some ways to enhance rapid eye movement sleep beyond what you've covered up until now? - So I think there are probably two emerging data sets that I've been intrigued by.

One of which we've been doing some work on and it comes back to thermal. What I failed to mention is not just that you need to warm up to wake up, which you do, but you also need to warm up to REM sleep, but not too much. If you take an organism or a human being and you strip them of bedsheets and strip them of clothes so they're basically almost au naturel.

If you warm the body up to what we call the thermo neutral point. So it tends to be, and this sounds extreme and you don't have to do this because you're under sheets and that makes a world of difference. But if you warm the room to about 30 degrees Celsius, which gets close to at the surface ambient level for your skin, something that can bring your core body temperature up back up to operating.

Because I told you when you go, when you're in that deep sleep trigger zone, the middle zone, your core body temperature drops and it drops significantly. And to wake up, you have to warm up. But on the journey to warming up, you also have to get to thermo neutrality for you to have REM sleep.

If I keep you too cold, I can reduce the amount of REM sleep. If I get you too hot, I can impair the amount of REM sleep. So it's a Goldilocks phenomenon, not too little, not too much, just the right amount. If I keep you there in terms of your thermal net neutrality, I can boost your REM sleep.

Now that's fiendishly difficult when you're trying to solve that equation as a commercial device, because different people are under different blankets, they run at different hot temperatures, they've got different partner situations. So you need a closed loop system again. But it's something that we're very interested in because almost all of the methods that I've described, and you are smart to pick this up, all target deep non-REM sleep.

But we spoke about in the first episode, every stage of sleep is important. And in subsequent episodes, I'll tell you exactly why REM sleep is so critical. So how can we boost that? That's one way that we're starting to explore it, but nothing, I think, solid yet. The other is some of the drugs, the newer sleep medications that have come onto the market.

And again, I think I mentioned I did take the task and I feel perhaps rightfully so about the classic sleep medications that if you look at the scientific data, if you can avoid them, it's probably best to do so. - Things like Ambien, et cetera. - We call them the Z drugs 'cause they all start, they're sort of generic names, sort of start with a Z, you know.

Ambien, for example, has a Z at the start of it for its generic name, but I don't want to get into naming any necessarily. - That's all right, they'll come after me, not you. - Yeah, but for Ambien. What's interesting about those medications, again, they're in a class of drugs that we call the sedative hypnotics.

So again, sedation, not sleep. And also there's been some great work, again, by Dirk and colleagues. If I were to show you that electrical signature of your deep sleep, it does look as though those drugs kind of increase the amount of electrical activity in that slower deep sleep range, except once you go all the way to the far left to the slowest of those slow brain waves, which turns out to be the types of waves that are most beneficial for most health-related brain and body functions.

You get this huge dent in your electrical brainwave activity. It's almost as though those drugs take a bite out of that realm of electrical activity. And of course there are issues with daytime sleepiness and some safety-related issues. There's been health associations, not necessarily causal. And so I offered one scientific viewpoint of those medications in the book, and so be it.

It's not as though I'm anti-medication, as I said, and some of the new medications are very interesting. Brings me back to REM sleep. There's a new class of sleep medications called the DORAs, and it stands for, it's D-O-R-A, small S, and it stands for dual orexin receptor antagonists. Oh my goodness, mouthful.

That just sounds like word salad to anyone who's not a neuroscientist. Orexin, which is part of that set of words, is a chemical in the brain. And orexin became prominent with the study of narcolepsy. And what we, we as the Royal We, people like Emmanuel Mignot and others at Stanford, what they discovered was that narcoleptic patients have a profound deficit in this chemical, orexin, and in the receptors.

- Also called hypocretin. - Also called hypocretin. And it has a function both, it turns out, for wakefulness and a function for feeding and eating-related behaviors. Hypocretin was probably more related to it when it was time, 'cause it was discovered right around the same time. - So early 2000s.

- And two different groups, yes, exactly, beautiful. Two different groups named it differently. But narcolepsy, as some people may know, is it's a condition, it's a sleep disorder. And one of the symptoms is called excessive daytime sleepiness, where you have inappropriate invasions of sleep during the day when you want to be awake.

Why? Well, it turns out that this chemical orexin acts like a finger on the light switch of all of the apparatus in your brain that switches on to force you awake. It reaches down into the, it's released from a central part of your brain called the hypothalamus, and it releases down into the brainstem to activate what we call the ascending arousal system, or the reticular ascending arousal system of the brain.

And when that lights up, it's like the light switch, which says on for waking brain activity. And so what was happening was that this orexin up higher up was not forcing the finger of wakefulness on during the day. So almost instead of a switch, which is what you want, it was more like a dimmer switch.

And you know, when you get to that dimmer switch point right in the middle where it's flickering, it's on, it's off, it's on, it's off, that's almost the state in which the narcoleptic brain was because they had a deficiency of orexin. So that was the orexin story in narcolepsy.

So why is it relevant for insomnia? Well, people realized the problem with narcolepsy is that they're asleep during the day when they want to be awake. But the opposite problem is true of insomnia patients. They want to be asleep at night, but they're awake. So why don't we selectively develop a drug that goes after this finger that flips the light switch on for wakefulness, but now let's block it at night.

So we flick the switch back in the off position, we turn out the lights for the brain, and we remove the problem of insomnia, which is excessive wakefulness at night, which is one of its problems. And therefore, when you remove that, indirectly what comes in its place is this thing called more naturalistic sleep.

And that's why it's been more favored now as the principal drug. It's still not necessarily well known by physicians or it's not very well prescribed. It's not very well covered here in the United States, unfortunately, with insurance. So it's a very expensive option right now. Health providers will choose not to do that, unfortunately.

So what's interesting about that drug though, is that it's mixed in terms of the studies, but quite reliably, it does seem to improve sleep, very much so, but it seems to, unlike those classic sleeping pills, which artificially look like they're increasing deep sleep, even though they're not, they're doing sedation.

These drugs can improve most all aspects of sleep, but including REM sleep, which those classic sleeping pills did not. Why is it doing that? We still don't know, but one of the things that these DORA drugs do that block the orexin, take off the on position of the light switch and flip them off, when you switch it off, it can actually then allow the activation or the stimulation of something called melanin concentrated hormone or MCH in the brain.

And that, when it is triggered on, can stimulate another chemical called acetylcholine in the brain, which is a neurotransmitter. If there is one neurotransmitter in the brain that seems to be responsible almost exclusively for this thing called REM sleep, or dominantly I should say for REM sleep, it is acetylcholine.

And this was discovered way back in the 1970s by my former, one of my former mentors, Alan Hobson at Harvard. And what this drug may be doing is indirectly boosting the amounts of acetylcholine in the brain, particularly in a region of the brain called the basal forebrain, which is a REM sleep regulating region.

And that's the reason that you get boosts in REM sleep. And people also report dreaming a little bit more too on those medications. So thermal manipulation, getting you to net neutral thermal zones helped increase REM sleep. But also there are some medications that were not necessarily designed for REM sleep enhancements selectively, but there is evidence that they do that.

So if you ask me, where are we at with REM? It's certainly more bereft of methods than deep non-REM sleep, but we are starting to find some now. - Given what you just told us about the role of acetylcholine in rapid eye movement sleep, what about taking precursors to acetylcholine?

I mean, certainly a good number of them exist, even like over-the-counter supplements like alpha-GPC. And then of course there are choline donors and things like that that can increase cholinergic transmission. Does that get into issues of, if one does that globally, is it possible that you increase arousal and have trouble falling asleep?

Because some of those cholinergic agents can be activating. - Can be quite activating. So that's one of the problems. The second is you may stop because you're going to have to take them before bed. You may brute force REM sleep to arrive earlier and you may therefore come at the cost of deep non-REM sleep.

And so you'd have to get some kind of timed release capsule, which you can do. You can coat these capsule and you can get a timed release and you would want to take it before bed. And then maybe after about four or five hours, you would want to kick it into gear because now you're in.

So it's a little bit, it gets a bit tricky. - Yeah, this is one of the reasons why I personally, this is just my experience. I'm not a fan of supplements that tap into the serotonergic system for sake of sleep because certainly serotonin plays an important role in sleep but anytime I've taken something, 5-HTP or something like that to try and improve sleep, I find that I fall asleep and then I wake up very deep, deep sleep and then I wake up very alert and I have trouble with the later phases of sleep.

And I think that is because yes, serotonin is involved in sleep, but it's involved in sleep at a very specific point in this, as you refer to it, this like symphony or ballet of different sleep stages and how they evolve and interdigitate with one another across the night. So, while I do think there are things that one can use pharmacologically or supplement based to improve sleep, generally, I like to think of those as the kind of thing that kind of pushes away front of the whole sleep process as opposed to trying to tap into one specific neurotransmitter within the sleep ballet.

- Exactly. Yeah, I like that way of thinking and you do have to be careful because in biology, it's often rare that there are any free lunches in truth. Nature has optimized our systems so exquisitely that when you start to try and gain the system for one thing, be very mindful that it may come at the cost of something else.

And that's why whenever we're doing these types of sort of developments of technologies for sleep, we are very cautious, not just to say, did we improve the thing that we're targeting? But first call of business in medicine is not will this drug help you, but firstly, is there any downside in terms of will this drug hurt you?

And then you have to understand the cost ratio benefit between those two things. - Yeah, just one more anecdote that is in agreement with what you said. Nowadays, there's an increased excitement around peptides, the use of peptides. - There is, yeah. - And I currently don't use any, but I did a short run with occasional use of cermorelin, which is a secretagogue, which is a growth hormone.

- That's right. - It promotes the secretion of growth hormone, not growth hormone itself. I took it not many times and I was tracking my sleep. And what I noticed is it put me into a little bit of a hypnotic state. Dreams were very intense, but deep, deep sleep.

But according to my sleep tracker, and I only ran this for maybe three nights, according to my sleep tracker, it completely eliminated all my rapid eye movement sleep, at least as measured by the sleep tracker. But the amount of deep sleep, of slow wave sleep, just like massively expanded.

So that can't be good. That can't be good. - No, you don't want to mess with that cocktail ratio that we described in the first episode. We presume that it's emerged as the correct Da Vinci code of sleep stage recipes. And there may be a time and a place where you want to over-index on one of those things for whatever reason, but to do it consistently and permanently, I would again say, if you think within the space of a lifetime that you know something that, 2.6 million years of evolution has not understood, chances are you're probably wrong.

- I agree. And certainly later in this series, we will touch into some of the over-the-counter supplements and other things that one can do in order to augment sleep that do seem to have some benefit because there are such things. But in the meantime, thank you for providing this incredible arc of description of basic sleep hygiene and regularity, light, dark temperature, getting out of bed when you can't sleep, alcohol, food, caffeine, cannabis, unconventional protocols, and let's call them advanced protocols, electrical protocol, brain stimulation, in other words, thermal manipulation, auditory stimulation, kinesthetic, and then these rapid eye movement enhancing drugs and on and on.

Matt, I can't thank you enough. This has been just replete with actionable tools and considerations, and I love that you took us to the cutting edge of what's happening now. I think it's wonderful to talk about the history of the field and what was discovered. It's wonderful to talk about the present, but it's wonderful that you've put our eyes a bit into the future of what the technology for sleep enhancement and monitoring holds.

So once again, thank you. - You're so welcome. - If folks haven't already seen or listened to episode one, highly recommend they do. And of course, we will be back soon with episode three, which is going to get into all the science and actionable protocols related to napping and caffeine and some other exciting things that I know impact people's daily lives and that they can get moving on should they choose right away.

And by moving on, I mean to sleep. - Thank you again, a delight. Cannot wait for the next recording. - Thank you for joining me for today's episode with Dr. Matthew Walker. To learn more about Dr. Walker's research and to learn more about his book and his social media handles, please see the links in our show note captions.

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