How Does Blue Light & Other Light Affect Your Sleep?

00:00:00.000 | So now let's talk about what I'm calling critical period

00:00:05.000 | three of each 24 hour cycle.

00:00:09.180 | So this would be the period of time of late evening.

00:00:12.040 | So it might be 6 p.m. for some,

00:00:14.600 | depending on when you go to sleep or 7 p.m.

00:00:16.640 | extending into the hours in which you decide to get into bed

00:00:20.600 | and go to sleep.

00:00:21.440 | And then throughout the night,

00:00:22.920 | there are a number of things that you're going to want to do.

00:00:24.800 | And there are a number of things that you are going to want

00:00:27.320 | to avoid doing in order to optimize your sleep.

00:00:30.280 | First of all,

00:00:31.160 | you're going to want to avoid bright artificial lights of

00:00:35.860 | any color.

00:00:37.120 | Yes, of any color.

00:00:39.100 | We haven't talked a lot about blue blockers, you know,

00:00:41.000 | lenses that block blue wavelengths or short wavelengths of

00:00:44.200 | light.

00:00:45.240 | I don't have anything against blue blockers.

00:00:46.920 | In fact,

00:00:47.760 | many people find that blue blockers provide them some relief

00:00:51.120 | from headache and some eye strain if they wear blue blockers

00:00:54.080 | throughout the day and certainly at night,

00:00:55.480 | but you don't need them.

00:00:56.960 | And even if you do wear them,

00:00:59.100 | you will find that if lights are very bright,

00:01:01.440 | it doesn't matter if it's a blue light,

00:01:02.600 | a yellow light, or a red light,

00:01:04.400 | those bright lights will wake up your brain and body.

00:01:07.720 | They will activate the same mechanisms that were activated

00:01:10.880 | early in the day by sunlight.

00:01:12.540 | However, and here's the really diabolical twist.

00:01:15.560 | I mentioned this earlier,

00:01:16.400 | but the diabolical twist in the way that your brain and body

00:01:19.400 | respond to light is that early in the day,

00:01:22.280 | in the morning hours,

00:01:23.120 | you need a lot of bright light ideally from sunlight to be

00:01:25.360 | very alert and to wake up.

00:01:27.600 | But in the evening hours and nighttime hours,

00:01:30.000 | it takes very little light,

00:01:32.320 | very few photons in order to wake up your brain and body and

00:01:36.320 | to disrupt your circadian clock and disrupt your sleep.

00:01:39.420 | So what that means is that once the sun goes down,

00:01:42.500 | which of course is going to happen at different times of

00:01:46.320 | year in different places on earth,

00:01:47.960 | but once the sun goes down,

00:01:49.640 | you would be wise to try and dim the lights in your indoor

00:01:52.960 | environment most days, right?

00:01:54.520 | I realized some nights you're going to throw a party and

00:01:56.000 | have people over, you might not want to dim the lights.

00:01:58.000 | Some nights you're going to go out.

00:01:59.360 | You might view a lot of bright lights,

00:02:00.600 | but most nights of your life,

00:02:02.560 | you're going to want to dim the lights in your internal

00:02:06.280 | environment.

00:02:07.480 | And ideally the lights that you do use,

00:02:09.640 | you would place low in that physical environment.

00:02:11.860 | So you would try and not use overhead lights,

00:02:14.060 | but rather rely on desk lamps or lights,

00:02:16.560 | even place low to the floor, even on the floor.

00:02:19.060 | If you are going to use light at night, and most people do,

00:02:23.960 | I would encourage you to use as little artificial light as

00:02:26.760 | is required to carry out the activities you need to require

00:02:29.800 | safely.

00:02:30.860 | That could be studying in which case you might need a

00:02:32.520 | little bit more light in order to read or study.

00:02:35.080 | If you're watching a television show,

00:02:37.160 | or you're watching something on your computer,

00:02:38.960 | dim that screen way, way down as dim as possible.

00:02:41.960 | While still, of course,

00:02:42.840 | being able to view what you need to view even better.

00:02:45.880 | I should say, ideally,

00:02:46.840 | you would use candle light and or moonlight.

00:02:49.160 | Now some nights the moon is really bright and you actually

00:02:51.440 | can use moonlight to go about your usual activities.

00:02:54.400 | Moonlight might seem very, very bright,

00:02:56.960 | but actually moonlight is fairly low light intensity.

00:03:01.800 | And candle light, which can also seem very bright,

00:03:04.420 | actually is very low light intensity.

00:03:06.880 | If you're sitting across the table with some candle light

00:03:09.920 | there, and it's a really bright candle,

00:03:11.760 | chances are it's only about three to 10 lux,

00:03:14.980 | which is very, very little light energy compared to say an

00:03:18.680 | artificial desk lamp or an overhead light,

00:03:20.560 | which is going to be in the area of anywhere from a hundred

00:03:22.800 | to a thousand lux.

00:03:24.680 | So candle light is fine, of course,

00:03:27.280 | be cautious with open flame, but candle light is fine.

00:03:30.200 | Moonlight is fine.

00:03:31.240 | Dimming artificial lights is fine,

00:03:33.320 | provided they're dimmed way, way down.

00:03:35.280 | And again,

00:03:36.560 | try and avoid using overhead artificial lights.

00:03:39.420 | The absolute worst lights are going to be overhead

00:03:41.560 | fluorescent lights of the sort that you would have in the

00:03:43.920 | supermarket or that you would see at a gas station or

00:03:47.600 | something of that sort.

00:03:48.720 | And I confess there are times in which I'm, you know,

00:03:51.120 | driving home and it's late at night and I want to be able to

00:03:54.240 | get to sleep and I'll need to stop at the grocery store or a

00:03:56.920 | gas station or something like that.

00:03:58.120 | I've actually put on sunglasses at night in order to avoid

00:04:01.200 | getting that bright light exposure at night.

00:04:04.120 | Although that's a little bit extreme.

00:04:05.840 | I have done that from time to time because that bright light

00:04:08.240 | exposure will absolutely quash.

00:04:10.400 | It will eliminate any melatonin that happens to be

00:04:13.960 | circulating in your brain and body.

00:04:15.400 | Now, melatonin, a lot of people think of as a supplement,

00:04:17.600 | but melatonin is naturally released as the evening comes

00:04:21.080 | about and into the nighttime hours,

00:04:22.760 | it's a hormone that makes you feel sleepy and allows you to

00:04:25.680 | fall asleep.

00:04:26.520 | So viewing bright light in the late evening hours and

00:04:29.400 | nighttime hours is really not good for your sleep quality

00:04:33.520 | and your ability to fall and stay asleep.

00:04:36.040 | So for most people,

00:04:37.360 | a simple rule of thumb is going to be avoid bright

00:04:39.880 | artificial lights of all colors.

00:04:42.120 | And in particular overhead bright artificial lights between

00:04:44.520 | the hours of 10:00 PM and 4:00 AM.

00:04:46.680 | That's right between 10 PM and 4 AM avoid those bright

00:04:48.960 | artificial lights as much as possible.

00:04:51.320 | Use only as much light as is absolutely necessary in order to

00:04:55.360 | carry out the routines and activities you need to carry out

00:04:58.140 | safely.

00:04:58.980 | I should mention that the reason overhead lights are

00:05:00.840 | problematic is the same reason why sunlight is so great

00:05:04.680 | early in the day, which is that the cells,

00:05:06.640 | that is the neurons that can wake up your brain and body

00:05:10.520 | through activation of the circadian clock reside mainly in

00:05:13.560 | the bottom half or two thirds of your neural retina.

00:05:16.240 | And the way the optics of your eyes work is that the cells on

00:05:19.440 | the bottom half of your eye view the upper visual field.

00:05:22.000 | So this is a beautiful adaptive mechanism that allows these

00:05:25.760 | cells to respond to overhead light from sunlight in the

00:05:30.360 | early part of the day and throughout the day.

00:05:32.200 | But in the evening,

00:05:33.320 | if you have bright artificial lights on and those bright

00:05:35.640 | artificial lights are overhead lights,

00:05:37.320 | it's going to more closely mimic what sunlight does in the

00:05:41.780 | evening time.

00:05:42.620 | And that turns out to be a bad thing if your goal is to

00:05:44.420 | eventually go to sleep.

00:05:45.680 | So again, do like the Scandinavians do use lights that are

00:05:49.240 | set low in the room at night.

00:05:51.120 | And if you really want to optimize your sleep-wake cycles,

00:05:54.160 | I suppose you could also do the opposite throughout the day.

00:05:56.520 | You could really emphasize the use of bright artificial

00:05:58.920 | lights and sunlight that comes from above.

00:06:01.020 | And of course, sunlight always comes from above,

00:06:02.920 | but if you're working in a given, you know,

00:06:06.120 | office environment and you know,

00:06:08.020 | it's 2:00 PM or 3:00 PM and you want to be as awake as

00:06:10.520 | possible, really crank up the overhead lights.

00:06:12.580 | And then in the evening is,

00:06:13.860 | which is this critical period three that we're referring to

00:06:16.160 | really try and dim those lights or have them off,

00:06:19.140 | or just rely on candlelight or moonlight from the hours of

00:06:21.500 | about 10:00 PM until 4:00 AM.

00:06:24.320 | Our good friend Samer Hattar,

00:06:25.580 | who's been on this podcast before.

00:06:27.120 | Samer is director of the chronobiology unit at the national

00:06:29.660 | institutes of mental health.

00:06:31.260 | Well,

00:06:32.100 | he's absolutely obsessive about this light stuff and

00:06:34.300 | avoiding light at night.

00:06:35.140 | In fact, he lives in what I joke is like a cave at night

00:06:39.500 | from 9:00 PM until 5:00 AM,

00:06:41.420 | which is really his kind of sleep cycle.

00:06:44.420 | He has his house so dark that you'd be lucky to be able to

00:06:47.460 | find a spoon in the kitchen.

00:06:48.980 | In fact, you'd be lucky to find your way down the hallway if

00:06:50.900 | you're me, but in any case,

00:06:52.700 | dim the lights from them way, way down.

00:06:54.660 | It will serve you well.

00:06:55.580 | It will make it much easier for you to get sleepy and stay

00:06:59.620 | sleepy and fall asleep and stay asleep throughout the night.

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How Does Blue Light & Other Light Affect Your Sleep? | Dr. Andrew Huberman

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