EVERY SPOKEN WORD
90 min read · 17,605 words- 0:00 – 2:19
Intro
- PAPeter Attia
[upbeat music] Hey everyone, welcome to "The Drive" podcast. I'm your host, Peter Attia. This podcast, my website, and my weekly newsletter all focus on the goal of translating the science of longevity into something accessible for everyone. Our goal is to provide the best content in health and wellness, full stop, and we've assembled a great team of analysts to make this happen. If you enjoy this podcast, we've created a membership program that brings you far more in-depth content if you wanna take your knowledge of this space to the next level. At the end of this episode, I'll explain what those benefits are, or if you wanna learn more now, head over to peterattiamd.com/subscribe. Now, without further delay, here's today's episode. [upbeat music] Welcome to another episode of "The Drive." As we've released so many episodes over the past four years, we realize we've covered a lot of topics in detail. Sometimes it can be hard to kinda keep up and try to piece it together. We also realize that there are listeners today who weren't exactly listeners a year ago or three years ago or four years ago. So we did a test of this idea back in May of twenty twenty-two where we did an episode that pulled a variety of clips from previous podcasts, but all on one topic, which was exercise. The feedback we received from that episode was overwhelmingly positive, and people asked for more. So this week we're going to do it again. And of course, we're gonna pick a different topic. This topic is going to be sleep, probably something we get just as many questions on as, frankly, anything else. We put these clips in the order of what we think is the best way to listen from top to bottom, but in between some of the clips, I'm gonna provide a little bit of commentary to set the stage. Our hope is that this will not only allow you to understand the topic of sleep better, but also help identify some of the previous episodes in case you actually wanna go back and listen to those in more detail. In each of these clips, I'm gonna be joined by sleep expert Matt Walker. Matt has been on the podcast several times, including three AMAs. One thing to note is that some of these clips are from AMAs, so if you're not a subscriber, you'll actually get a sense of what we cover during those episodes. This is still a new concept, and this is only our second time doing this, so we really do want the feedback. If you like this, tell us. We'll keep doing it. If you don't, we'll scrap it. So without further delay, I hope you'll enjoy this special episode of "The Drive." [upbeat music]
- 2:19 – 10:05
Evolutionary reasons to sleep
- MWDr. Matthew Walker
Firstly, you know, it took Mother Nature three point six million years to put this eight-hour thing called a night of sleep in place. And within the space of seventy years, if you look at the data, we've lopped off almost twenty to twenty-five percent of that. You know, imagine coming along and saying, "You know, in the next hundred years, I think what I'm going to do is for the entirety of human society, I'm going to reduce their oxygen saturation by about twenty to twenty-five percent." Do you think that's a good idea? And [chuckles] the answer is no.
- PAPeter Attia
No, it, it's such a great example. I'm, I'll pause for a moment just to tell a funny story that you, you and I have talked about off mic, which is up until about twenty twelve, I was in the I'll sleep when I'm dead camp. And I, I know what led to that. It wasn't... Th-there was a very deliberate decision at the end of medical school when a, a good friend of mine with all the best intentions, who was a year ahead of me, so he was now in, at the end of his internship as I was about to begin mine. He said-- and this is in the days when we didn't have the eighty-hour work week requirement in residency, so we averaged, I think about a hundred and fourteen hours a week in the hospital. So he said to me, "Look, Peter, you're, you're signing up for, you know, whatever, five, seven years of this thing. If you spent every moment outside of the hospital sleeping, you would still be tired. The only difference is you wouldn't have any fun. So make sure you live every moment that you're not in the hospital to the fullest." And so for me, that basically meant if I wasn't in the hospital, I was swimming, I was going out with my friends, I was trying to meet girls. Like any-- I was doing anything and everything, such that during that period of my life, I, I just know, 'cause I was pretty adamant about recording how much time... Like, I was very wed to this idea, there's a hundred and sixty-eight hours in a week. If I'm spending, you know, a hundred and fourteen of them here, and I spend this many driving, and I spend this many getting groceries, and I spend this many swimming, and blah, blah, blah, blah, blah, I think I, I was about twenty-eight hours a week of sleep. So it wasn't four every night because you'd have none, and then six, and then three, and then eight. Like, you, you could binge sleep from time to time. But it was pretty much twenty-eight a week. I'll come back to some of the implications of that. But fast-forward a few years, I'm talking to a good friend of mine who's a physician who, like you, is adamant about, you know, the importance of sleep. And we're having dinner one night, and he says-- he's challenging me on this, and he says, "So let me get this straight. You've just decided that you're gonna sleep half of what is evolutionarily programmed." And I said, "Yeah." He goes, "Does it strike you as odd that evolution would have designed us to spend a third of our life not mating, not watching out for predators, not hunting for food, but doing this thing for some other purpose? Do you think that thing must have been important?" And it was s-such an obvious argument, but it really overnight changed the way I thought about this, which was evolution went to great lengths to do this and superficially at great cost to us, right? I mean, you could argue, well, imagine you didn't need to sleep and you could spend twenty-four hours a day foraging for food or a mate or some other thing, but it didn't. So it's sort of, it's sort of like there's probably a reason we are not anaerobic [chuckles] to your point about reducing oxygen saturation by twenty-five percent.
- MWDr. Matthew Walker
You know, if you were to think about that, you know, during sleep, just as you said, you're not eating, you're not finding food, you're not finding a mate, you're not reproducing, you're not caring for your young, you're vulnerable to predation on any one of those grounds, but especially all of them put together as a collective.
- PAPeter Attia
It's completely anti-evolutionary.
- MWDr. Matthew Walker
It, it, it sounds like the dumbest thing. And, you know- I've often said, and it has been said before, if sleep doesn't serve an absolutely vital set of functions, it's the biggest mistake that the evolutionary process has ever made. And we now realize from this constellation of evidence that Mother Nature did not make a spectacular blunder in putting this thing called an eight-hour sort of need of sleep in place. It is the greatest life support system that you could ever wish for. It is a remarkable health insurance policy, and what's great is that it's largely democratic, it's mostly free, and in terms of a prescription from a doctor, it's largely painless.
- PAPeter Attia
[laughs]
- MWDr. Matthew Walker
So I almost wanted to title the book Consciousness Is Overrated [laughs]
- PAPeter Attia
[laughs]
- MWDr. Matthew Walker
Or just Sometimes... Consciousness Is Overrated. But when you really look at the evidence in terms of risk-- de-risking just about every disease that is killing us in the developed world, it's very hard to look no further than sleep. And that's why I don't want to trivialize diet and I don't want to trivialize movement and activity. But what I would say is that if you want to put sleep up against either one of those two and kind of play the whole head-to-head game, which I don't think we need to do here, I would simply say that sleep is the foundation on which those two other things sit. It's not the third pillar of good health. I think it is the foundation.
- PAPeter Attia
That's a really interesting way to think about it because I typically describe four pillars, or five if you include all of the exogenous molecules that you could lump together. But another way to think about it, which again, I don't think is necessarily the right way to think about it, but sometimes it makes the point, if you deprive yourself of food, how long can you survive? Well, we have one person up to three hundred and eighty-two days. Even someone who's as lean as you could survive thirty days with no food. How long could you survive without water? Depends greatly on the temperature, et cetera. But you could make the case that deprivation of sleep would result in the quickest reduction of health, certainly more than not eating or not exercising for, you know, a period of time.
- MWDr. Matthew Walker
And those studies have been done in rats.
- PAPeter Attia
Yeah, and actually we know some of this from humans who have been trying to-- I-- in fact, didn't the Guinness Book of World Records-- I can't remember if I read this in your work. They've actually banned-
- MWDr. Matthew Walker
Yeah
- PAPeter Attia
... attempts at longest period of sleep deprivation.
- MWDr. Matthew Walker
So I mentioned this, yeah, in the book-
- PAPeter Attia
Yeah, you might-- it was in the book, yeah
- MWDr. Matthew Walker
... that there was a time when you could still try and beat the world record of sleep deprivation, and it got up to about sort of, I think the last true effort was about twenty-four days, uh-
- PAPeter Attia
Oh my God
- MWDr. Matthew Walker
... but I, I think it was debatable, that one. But based on the weight of the scientific data, the relationship with-- between sleep loss and mental health, sleep loss and cancer, sleep loss, cardiovascular disease, sleep loss and metabolic syndrome, Guinness started to feel very, very uncomfortable. And then when suicide came on the table, it pulled it. So in other words, think about this. You know, there was a gentleman, Felix Baumgartner, I think his name was, who, sponsored by Red Bull, went up in a capsule-
- PAPeter Attia
Mm-hmm
- MWDr. Matthew Walker
... in a hot air balloon to the outer surface of our planet.
- PAPeter Attia
This was about four years ago.
- MWDr. Matthew Walker
Four years ago.
- PAPeter Attia
This was remarkable.
- MWDr. Matthew Walker
He opened the door, and then he jumped out, and he fell back down to Earth at over a thousand kilometers an hour. Using his body alone, he broke the sound barrier, and he successfully came down. And now Guinness says for that, just fine.
- PAPeter Attia
[laughs]
- MWDr. Matthew Walker
However, [laughs] to sleep deprive yourself, no. Much more unsafe.
- PAPeter Attia
Right.
- MWDr. Matthew Walker
We're not going to let it happen.
- PAPeter Attia
You are allowed up to-
- 10:05 – 25:42
Stages of sleep, sleep cycles, and brainwaves
- PAPeter Attia
So let's shift gears just a little bit and go back to the polysom. Let's explain to people, 'cause we're gonna eventually have to talk about tracking these things, and I wanna bring up some of the sort of commercially available ways that people do that, which I think by definition are still not accurate enough for people to, you know, compare them to their polysom. But if I came into your lab tonight and I was willing to go to sleep there and you would hook me up to an EEG, what are the different patterns of brainwaves and how would you morphologically describe them and then bucket them by these stages? You've already sort of touched on a little bit is deep, REM, deep REM, deep non-REM, et cetera.
- MWDr. Matthew Walker
Yeah. So upon falling asleep, human beings, and in fact all mammals, will experience two different stages of sleep. One of them is called non-rapid eye movement sleep. The other is rapid eye movement sleep. Non-REM sleep has been further subdivided into four separate stages, which are unimaginatively called stages one through four.
- PAPeter Attia
Thank God.
- MWDr. Matthew Walker
Yeah, I know, yeah. [laughs] I think that's all that the sleep-deprived people who are, you know, experimenting could come up with at that time.
- PAPeter Attia
[laughs]
- MWDr. Matthew Walker
Um, so increasing in the depth of steep-- sleep, so stages three and four of non-REM sleep are the really deep restorative stages of sleep. Stages one and two are the lighter stages of sleep. And then on the other hand, we have rapid eye movement sleep or REM sleep, which is named not after the popular Michael Stipe pop band, but because of these bizarre horizontal shuttling eye movements that occur during this stage of sleep, these rapid eye movements. So you have these two different types of sleep, and they will essentially, as you fall asleep here in-- at the sleep center at Berkeley, they will go into essentially a battle for brain domination throughout the night. And that cerebral war between non-REM and REM is going to be won and lost every ninety minutes and then replayed every ninety minutes to create what we call a standard cycling architecture of sleep or what we call a hypnogram of sleep. And so what you will see is that upon falling asleep, you'll go into the light stages of non-REM, stages one and two-
- PAPeter Attia
Oh, before we do that, let's say before I fall asleep, when I'm just laying in the bed How would you describe my brainwaves under the wakeful condition?
- MWDr. Matthew Walker
So at that point, what we typically see is that when you close your eyes, the back of the brain goes into what's called an alpha rhythm. So when you're awake, your brain shows this remarkably frenetic, high-frequency electrical activity. In other words, your brain is going, in terms of its brainwaves, it's going up and down many, many times a second. And it's-
- PAPeter Attia
And, and the amplitude is-
- MWDr. Matthew Walker
And the amplitude is very small
- PAPeter Attia
... small
- MWDr. Matthew Walker
Which kind of is paradoxically to think, "If I'm awake, then my brain is active, and so the size of those brainwaves should be big." It's not. It's actually very small, and here's the reason. Different parts of your brain are doing different things at different times, so those brainwaves sort of are all canceling each other out. So what... The, the analogy would be if I were to dangle a microphone above a sports stadium, what I'm picking up is the signal from the, the crowd of 100,000 individual neurons that sit underneath it. That's how an EEG electrode is. Now, before the game starts, that's wakefulness, and at that point, the 100,000 people in the stadium, the 100,000 brain cells, they're all speaking to each other at different moments in time.
- PAPeter Attia
So there's a lot of cancellation.
- MWDr. Matthew Walker
So there's a lot of cancellation. They're not all coordinated, but it's very fast and frenetic, so I just get this signal that is very desynchronized. And it's not synchronous, so they're not summing their power together, so the size of that brainwave is not very big. But it's going up and down-
- PAPeter Attia
But that's why the frequency is so high
- MWDr. Matthew Walker
... the frequency is high, meaning that you're sort of going up and down maybe 50, 60 times per second. Now, as you start to fall asleep, or actually even before you start to fall asleep, as you're lying in bed awake, the back of the brain is the first part of the brain that really starts to settle down. It goes into what we call alpha rhythm when you close your eyes.
- PAPeter Attia
And I assume that's just because the occipital cortex is in the back and you've closed your eyes.
- MWDr. Matthew Walker
Brilliant. So the back of the brain, visual brain, if you close your eyes, that part of the brain essentially stops processing the outside world, and it goes into its sort of default state when it's awake of slowed frequency. It drops down from maybe 50 times per second down to about, let's say, 10 cycles per second.
- PAPeter Attia
But still relatively low amplitude?
- MWDr. Matthew Walker
But still relatively low amplitude. Then once you start to actually transition, when you make that bridge from the world of wakefulness to sleep, as you sort of cross through that window from one of those worlds to the next, something bizarre happens. And if anyone out there is lucky enough, um, to be listening to this and they have a bed partner, you can actually see this. Just look at their eyelids as they're falling asleep, and what you'll see is that their eyeballs start to roll in their sockets, and they're called slow rolling eye movements. Now, we don't know why the eyes roll in the sockets like that, but it's the first sign that you're making the transition from the world of wakefulness into sleep. We use it as almost an indicator of the transition into sleep. Now, by the way, if your partner wakes up, sometimes people wa- will wake up from that state, and they see you just looking over them in bed, staring at their eyelids. If you're in, early in a relationship, it's usually the end of the relationship.
- PAPeter Attia
Yeah. Yeah, that's-
- MWDr. Matthew Walker
Just a point of note. Please don't blame me. Usually wait till you're married and then start to do that one. [laughs]
- PAPeter Attia
[laughs]
- MWDr. Matthew Walker
The divorce usually is harder to come by. So then you start to go down into the light stages of non-REM sleep, stages one and two. Then after about 20 or so minutes, you'll go down deep into stages three and four of non-REM sleep.
- PAPeter Attia
And, and in one and two, have we transitioned out of that alpha wave? I mean-
- MWDr. Matthew Walker
Yes
- PAPeter Attia
... where do we start to see the, uh-
- MWDr. Matthew Walker
Already
- PAPeter Attia
... thetas and-
- MWDr. Matthew Walker
Theta already happening in stage one. In stage two, you actually go into theta activity, which is now down from 50 cycles per second, maybe down to just sort of six or seven cycles per second.
- 25:42 – 36:25
Understanding sleep chronotypes and how knowing yours could help you
- PAPeter Attia
Matt, last time we sat down, you, you talked briefly about the sleep chronotypes and, and I've found this interesting for basically two reasons. One is just observing probably a migration in my own daughter's chronotype, which is as she's getting older, she's sleeping in longer in the mornings and going to bed later and later. And I know that as she gets closer and closer to being a teenager, that's probably going to increase. But also just more cognizant, I think, of other people. Uh, you've alluded to it briefly earlier, which is like there are just people who are gonna go to bed later and wake up later, and it doesn't mean that they're, that there's anything wrong with that or there's anything wrong with the reverse, which is people who go to bed early and wake up really early. So kind of wondering if there's a way to actually know what chronotype you are beyond just observation, because is it possible that the observation is not your optimal state? In other words, if you have somebody who's sleeping a certain way because their job is imposing it, but it's not the way that they're, you know, ideally meant to do it. Uh, let me give a better example. A student in college could easily drift into a later chronotype because everybody in their dorm room is, even though they may actually be more suited to be earlier. So how, how can one figure this out?
- MWDr. Matthew Walker
So there are genetic tests that will give you a stronger sense of your chronotype. So chronotype simply means, yeah, are you a morning person, are you an evening person, or are you somewhere in between? And somewhere between 25 to 30% of the population are morning types, 25 to 30% are evening types, and then the rest of us are somewhere in between. Sleep science has then gone a little bit further. We split it into five categories sometimes, which is extreme morning types, morning types, middle, evening types, and extreme evening types. We know that it is under strong genetic control for two reasons. First, there is a s- significant degree of heritability, so if you are a morning type, it's more than likely that one or both of your parents were morning types. Secondly, we now know that there are a collection of genes that will determine to a degree your chronotype, and this is why companies like 23andMe will tell you what type you are, or they will give you a probabilistic estimation of what type you are. Last count, I think from data from 23andMe and this data from the UK Biobank, there's about nine different genes that we know of right now that will contribute to your chronotype. Most of them are what we call clock genes. This refers to the fact that these genes control the rhythm of your circadian cycle. Now, those genes don't control necessarily the size of your circadian rhythm. In other words, how kind of strongly active and awake you are during the day and how deeply sort of down you go at night. These genes do something different. These genes control when that sinusoidal wave of your circadian cycle arrives on the clock face. What I mean by that is if you have a certain type of gene complement that makes you a morning type, your activation peak, your peak alertness is going to arrive earlier in the day, and your awesome downstroke of your circadian rhythm will arrive earlier in the evening. Whereas if you have a different combination of these gene composites, then you could be an evening type. In other words, your circadian rhythm looks very similar in its sinusoidal pattern, but when the peak and the trough of that circadian rhythm arrive on the 24-hour clock face is very different to a morning type. So we know that there is a complement of genes that you are given at birth that will determine, on average, once you're an adult, are you a morning type or are you an evening type? What you alluded to, however, for your daughter was something different, which is that no matter what chronotype you are, that innate chronotype rhythm that you have gifted by your genes will change as you develop from a young child to an adolescent teen to an adult to an older adult. In other words, you go from being much more of a morning type when you're a kid, even though you want to stay awake longer, you're found on the couch and you're carried to bed and you're fast asleep, to then being a teen where your chronotype fast-forwards in time. And this is a problem for early school start times, where you're putting kids to bed at 9:00 PM and saying, "You've got to go to bed because you have to wake up at five o'clock in the morning to catch a 5:30 bus for a 7:15 start time." Well, th- there's no point in saying that. It's not their fault that they're now in bed and it's 10:30, an hour and a half later, and they can't fall asleep as a 15-year-old because their chronotype has moved forward in time. They want to go to bed later and wake up later. Nothing they can do about it. It's biology. And then once they become an adult, it starts to shuttle back a little bit once they become sort of, you know, moderate age, 30 or 40. And then as we start to get older, we regress. [chuckles] That's why in Florida there's something called the early bird special, where people are going out for dinner at, you know, 4:00 PM or 5:00 PM because their chronotype has regressed back and they're in bed by, you know, 8:00 PM. So there are genetic tests to come back to your question. However You don't need to do a genetic test to get close to understanding what you are. There is a pencil and paper method that sleep scientists have developed, and you can Google it. It's called the MEQ test, and maybe I'll send you the link and we can put it in the show notes.
- PAPeter Attia
Yeah, we'll, we'll put it in the show notes.
- MWDr. Matthew Walker
And it's a very simple link that you just click, and it's a test. It probably takes about five or six minutes to fill out, and it's called the MEQ test, the Morning Eveningness Questionnaire test. And you go through, you answer a list of questions, and at the end you add up your score, and it will tell you what flavor of chronotype you are. And what's nice is that then they've pattern-matched this test and validated it against these gene, these genetic tests, and there's a pretty good correlation. It's not too far off. So this is the poor man's version of the 23andMe test if you want it, and we'll do a, a link in the show notes and you can take it, and that's a, a cheaper way, a pencil and paper method or an online method.
- PAPeter Attia
So the bigger question is, Matt, what do we do with this information, right? I mean, you, you've-- I think we did talk about this previously at one point, that you have a couple who have different chronotypes. That can be really difficult. They're going to bed and waking up at different times. You've already alluded to the problem of children who are, I, I think, being subjected to potentially too much early school, when in reality they probably would do better with later school. Is this the kind of thing that should factor into decisions people make about when they pick classes in college? Like, I mean, it seems like there seems to be, this seems to be one of those things where there might be a bunch of people that go through life kind of miserable when they don't have control over their schedule, as opposed to knowing this. And so would knowing this by itself provide a benefit to folks?
- MWDr. Matthew Walker
I think it would. I think it would explain a lot about why you struggle so much where other people seem to be just these Energizer bunnies, and they've even got time to go to the gym for an hour before they sit down at their office desk at 7:00 AM in the morning, and you're still on your fourth cup of coffee desperately trying to wake up, and you're struggling to make it in by seven 15, having woken up 20 minutes before. And I think the second thing that it helps with is realizing that you're not culpable. It's sort of non mea culpa. It's not your fault. It's, you can understand that this is genetic. 'Cause a lot of night owls have gone throughout life being chastised and thinking, "Well, if only I could get my act together and get to bed earlier and stop being what people tell me I am, which is slothful or lazy, you know, I could hold down a better job or..." And again, I think society needs to be much more understanding of it and also then modifying itself in response to accommodate it, and neither of those things I see in full-serving scoop sizes in society right now, and I th- that should change. And I think COVID is interesting because if there's some positive upside to it, it may have given us the chance for people to understand how much better they, they can sleep when they're closer in harmony with their own chronotype, rather than trying to work against it. Because when you fight biology, you normally lose, and the way you know you've lost is often through disease and sickness, and I think there is a version of that going on here. I also think it can sometimes explain incorrect insomnia. Often I'll hear someone tell me, if I'm sort of out in the public, they'll say, "Well, I suffer from insomnia. I get into bed, and I can't fall asleep, and I'm wide awake for the first hour and a half, and I need to take some sleeping pills." And then I'll, I'll say, "You know, firstly, I'm not a doctor, but let me just ask you a question. If you were on a desert island with no responsibilities, nobody f- to wake up for, nothing to do, and you could just sleep whenever you want and ge- get up whenever you want, what time would you normally go to bed?" And they would say, "Well, I would actually like to go to bed at midnight and wake up around eight o'clock in the morning, in truth, but I have to get up for my job. I have to wake up at 6:00 AM, getting in bed at 10:00 PM, but I still have this terrible insomnia." And I say, "Well, you know, I don't know this, but it's possible that what you could have is not insomnia, but a mismatch between your chronotype and your working life schedule, and you may want to explore some of this. And there's a test, an MEQ test," and I tell them about this, "and then go and speak to your doctor." So that's the second implication that I think comes from the question that you asked about how it impacts society. Once you know it, what do we do about it, and what should we be doing about it? Those are some of the ramifications I think. [upbeat music]
- 36:25 – 38:45
Defining sleep efficiency and how to improve it
- MWDr. Matthew Walker
I forgot to say in the episodes before, and I'd love to say it now, is about sleep opportunity versus duration. We've constantly been speaking about in our discussions how much sleep does a person need? What's the optimal amount? And we're speaking about somewhere between seven to nine hours. When I say that, I'm talking about seven to nine hours of sleep.
- PAPeter Attia
Not time in bed-
- MWDr. Matthew Walker
Correct
- PAPeter Attia
... where you might lose 10 to 15% of it.
- MWDr. Matthew Walker
Right. And this is the reason that when I think people who say, "Well, surely you can get by on six and a half hours of sleep or seven hours of sleep," you've got to be very careful 'cause that's a dangerous statement. This comes to something that we call sleep efficiency. Now, if you are in your 40s, you will probably have-- if you're healthy, you'll probably have a sleep efficiency of what we call 90%. In other words, of the time that you're in bed, 90% of that time is asleep and 10% of the time is awake. So let's take an eight-hour sleep period, and you think, "Well- I am in bed for eight hours, so I'm good. I'm getting my eight hours of sleep. That's not true. Eight hours of sleep is, what, that's 480 minutes if my math is correct. If you get a 10% loss of efficiency, it's like a heating system, you lose 10% of the-
- PAPeter Attia
Yeah, you're down to 712
- MWDr. Matthew Walker
... you're down to 712. So in other words, for you as a 40-year-old with a healthy sleep efficiency of 90%, for you to get eight hours of sleep, you need to be in bed for eight hours and 48 minutes.
- PAPeter Attia
Even a bit longer, actually.
- MWDr. Matthew Walker
Yeah, or even a bit longer. So you've got to be very careful. That's why I constantly speak about a sleep opportunity-
- PAPeter Attia
This is-
- MWDr. Matthew Walker
... of eight to nine hours in bed to get your seven to eight hours of total sleep, if that makes sense.
- PAPeter Attia
Yeah, and this is where I think devices like the Oura Ring are very helpful because that's where they're very good. They're very good at telling you, "You were in bed this long, but you're actually only asleep this long," and that's the number we want the patients to fixate on. We don't even look at time in bed when we give our patients feedback. We're talking about total sleep time and efficiency. So if there's a problem with total sleep time and efficiency is low, you have to improve the quality. If total sleep time is low and efficiency is high, you need more time in bed, and it's getting people to understand that distinction that's very important.
- MWDr. Matthew Walker
And the caveat there comes
- 38:45 – 41:38
Correcting insomnia: a counterintuitive approach
- MWDr. Matthew Walker
for people with insomnia, though, that I'm here saying you need to increase your time in bed, your sleep opportunity, as I call it, to make sure that you get the right total amount of sleep, and you have to accept there is inefficiency in the system, and you need to extend your time in bed to overcome that slight inefficiency. So again, sort of eight hours and 50 minutes to get your eight hours total sleep. The only time I would say that you should not be thinking about longer time in bed is if you're someone who is struggling with insomnia-
- PAPeter Attia
Right
- MWDr. Matthew Walker
... and you're lying in bed awake a lot of the time.
- PAPeter Attia
Reprogramming.
- MWDr. Matthew Walker
We actually do the opposite, which is we actually shorten your sleep opportunity. We crunch that down. It's one of the tools that we have in the CBTI toolbox.
- PAPeter Attia
That's right. So you, you wanna drive the efficiency up by taking-
- MWDr. Matthew Walker
Correct
- PAPeter Attia
... the denominator out.
- MWDr. Matthew Walker
People have lost their confidence in going into the bedroom and sleeping constantly soundly throughout the night. So what we end up doing is actually constraining them maybe down to just six hours of sleep opportunity. We put them on a diet of sleep opportunity rather than an extension, and very quickly what happens-- So it's ironic. You come to me and you say, "I'm not sleeping well," and I say, "Great. I'm going to have you sleep less." And you say, "Ridiculous," but it's not. What you do is by compressing that window down, you're sleeping less, and you're building up more of that sleep pressure because as a consequence of the reduction of sleep opportunity time, you're going to be awake during the day longer. The longer that you're awake, the more of that sleep pressure you build up. So firstly, you're coming into the following night with even more sort of sleepiness on your shoulders. And then secondly, I'm teaching the brain, unlike it's been giving, it's been given luxury time to just be awake as long as it wants to at night and maybe sleep some, and that's that phenotype of insomnia, awake time at night. By constraining that time, I start to force your brain to realize, "I'm sorry, you no longer have the luxury of having all of this time to sort of be awake and be asleep." And very quickly the brain starts to realize and learn that, in fact, it only has this tiny opportunity at the dinner table called sleep that is six hours, and now you start to brute force efficiency. The brain starts to realize, "My goodness, I've only got six hours. I need to get my sleep into that six hours." So efficiency markedly increases when you constrain total amount of time in bed. So it's this ironic way that we help treat insomnia. We constrain total sleep time. You brute force efficiency and a brute force response from the brain, and all of a sudden something magical happens. [upbeat music]
- 41:38 – 50:17
Pros and cons of napping, and insights from the sleep habits of hunter-gatherer tribes
- PAPeter Attia
Now that we've set the stage for what sleep is and why it's so important, the next set of clips will really look at ways in which we can improve sleep. These clips will look at the pros and cons of napping, proper sleep hygiene, and an ideal wind-down routine, optimal temperature for sleep, and how Matt changed his thinking on blue light. [upbeat music] The question now comes down to one of napping, which we did touch on in our previous episode, but I want to revisit it. Lots of times patients come to me and say, "Peter, you have no idea what a 20-minute nap does for me between 2:00 and 4:00 in the afternoon." And my historical response to that has been, "You know, gosh, you really shouldn't need a nap. I mean, if you're sleeping correctly, isn't that actually a negative thing because it's depleting some of that adenosine-based pressure, and wouldn't you be better off letting the pressure cooker cook and driving you into a deeper sleep when you first take your sleep?" So what are your thoughts on that type of a nap, that, that sort of short 20-minute, you know, late afternoon pre-dinner nap?
- MWDr. Matthew Walker
Naps really are a double-edged sword, and we've done lots of studies where we use naps to, to study the functions of sleep, and we see benefits from naps. Even naps as short as 17 minutes can produce learning and memory benefits. So there does seem to be some, some enhancement that you get, and you can see that from cardiovascular benefits as well. The downside of naps is that it can take away just what you described, which is sleep pressure. And so the typical recommendation that we have is the following: if you are struggling with sleep at night Avoid naps during the day. Because what you want to do if you are already having problems either falling asleep, which is what we call sleep onset insomnia, or you can fall asleep but you can't stay asleep, which is what we call sleep maintenance insomnia, you want to build up as much sleep pressure, as much sleepiness as you possibly can during the day. If you are struggling with your sleep at night, do not nap during the day, and the pressure cooker analogy is beautiful. Keep building up all of that healthy sleepiness pressure, because when you nap, it's like having the valve on the cooker open up and you just, pshh, you just release some of that healthy sleepiness. And now when it comes time to go to bed, you're not going to feel as sleepy anymore. However, on the flip side, if you are not struggling with your sleep and you can nap regularly during the day, the advice is naps can be just fine. Because in fact, if you take a step back from an evolutionary perspective and you study hunter-gatherer tribes whose way of life hasn't changed for thousands of years, they don't necessarily sleep the way that we do in modernity. In fact, particularly during the summer months, they will typically have an afternoon nap right in the time zone that you just described, and this is the v- very much the Mediterranean siesta-like behavior. And in fact, if I stick an electrode on both of our heads throughout the day and I monitor our physiological brainwave activity-
- PAPeter Attia
It'll stick much better to my head, by the way, than yours.
- MWDr. Matthew Walker
[laughs] Well, yeah, right now especially 'cause I've got this terrible COVID, uh, do which, uh, I look like I should be out of Buck Rogers and anybody who remembers that, uh, television show. But anyway, what we will see is that somewhere between about 2:00 to 4:00 PM, both you and I will have this kind of drop in our physiological alertness, in our physiological level of brain activity. In other words, as if as a species we're almost pre-programmed to have this enforced dip in our alertness. And so many people see this, you know, in the afternoon meetings around the boardroom table or wherever. You sort of get these ugly head nods that start to happen. It's not people listening to good music, it's just that people have this sort of they're falling asleep, they're falling prey to this what seems to be a genetically hardwired pre-programmed drop in our alertness, as if maybe we should be what's called biphasically sleeping as a species at times during the year rather than monophasically sleeping, which is how we do in most first world nations. In other words, one single bout of sleep at night versus two bouts of sleep, which is how those hunter-gatherer tribes sleep, especially during the summer.
- PAPeter Attia
And so Matt, would they sleep long enough in that 2:00 to 4:00 window that they would get a full 90 minutes, say, and get through a full cycle? And then if so, did that mean when they did their nighttime sleep, presumably they would stay up later and get maybe six hours in the evening instead of... You know, 'cause, 'cause people always talk about how, well, hunter-gatherer studies have always suggested that, you know, seven and a half to nine is the species required amount of sleep on average. But you're saying it was potentially broken into two chunks. Was that, was that afternoon daytime chunk or daylight chunk, call it, about 90 minutes?
- MWDr. Matthew Walker
No, it wasn't. It was actually typically shorter than that on that basis. But you're right. They typically are not sleeping what we currently recommend for monophasic sleep, which is the average adult should get somewhere between seven to nine hours. That's the recommended range that we, we all provide. But what they would typically do is they would maybe sleep just six, six and a half hours at night, and then they would make the rest up, and they would get into that exact same sort of territory by way of the nap. So they would take it in these two chunks. Now, I should note this is very different to something else that's been described in the literature, which is first sleep and second sleep. That activity does seem to have occurred during our historical past. It seemed to have emerged in the sort of Dickensian era. That was different, though. That was where people would sleep for the first four hours, then they would wake up in the middle of the night. They would, you know, write, they would drink, they would play music, they would make love, and then they would go back for another four hours of sleep. Did that happen? Yes, it seems to have, based on historical writings. But is that the way our physiology and our circadian rhythms are designed? No, it doesn't seem to be. There's usually one study that's cited that suggests maybe we should do that. But overall, the physiology that we know of for human beings doesn't seem to suggest that that was, that was more sociologically driven rather than biologically driven. Biologically, we may be biphasic, but very differently according to this hunter-gatherer sort of tribe hypothesis. By the way, the other thing that's interesting in those hunter-gatherers, and it comes on to what I think we described before, which is this concept of midnight. Most of us don't think of what the term means, but in those individuals it means what the word states, which is it's the middle of the night for them, [laughs] midnight. Because they usually go to bed maybe two hours after sundown and they're asleep, you know, by let's say 9:00 PM in, in the evening or 8:30, and then they're awake, you know, just a little bit before dawn. In fact, what's interesting, and maybe we'll get onto this in later discussions or we won't, but what seems to wake them up is not necessarily daylight. It's the change in temperature, because there's a rise in temperature that seems to happen before daylight starts to break. And it seems to be it's the temperature change that they are much more buckled to in terms of regulation of their sleep-wake rhythm. And so- The way in which the structure of their sleep, biphasic, is different to ours in modernity, and the timing of their sleep is different to some of our timing. You know, for many people, midnight is the, the time that you think, "Well, I should just check Facebook one last time," or, "I sh- you know, send my last text." Um, that's what midnight means. But normally for a [laughs] for a couple of, uh, thousand years, uh, or hundreds of thousands of years, it probably meant that was the middle of your solar cycle and it was the middle of your sleep cycle.
- PAPeter Attia
[laughs]
- MWDr. Matthew Walker
[laughs]
- PAPeter Attia
I'm glad I'm closer to our ancestors. Uh, if, if I could go to bed at 8:00 every night and wake up at 4:00, that is a perfect night of sleep for me. [upbeat music]
- 50:17 – 59:32
Sleep hygiene, wind-down routine, and tips for better sleep
- PAPeter Attia
Matt, and on previous episodes, obviously we went into some pretty good depth on tricks, tips, et cetera. Inside our practice, we have a whole sleep hygiene protocol, and we, we sort of run patients through it relatively early, especially if they're having any sleep issues. But do you mind just sort of going through where you are now and how you think about this? And again, I'll caveat this by saying you're not a sleep physician, so it is not your practice to be out there treating any one individual with respect to their sleep.
- MWDr. Matthew Walker
That's right.
- PAPeter Attia
But also you're, you're infinitely more qualified than virtually anybody to help people start to think through what the parameters are that factor into sleep, and that's the way we kind of explain it, which is, look, here are these five or six levers of sleep, and here's how you could move each of them in your control. But, but I kind of want to hear what, how you think of it.
- MWDr. Matthew Walker
Yeah. So I think in our past episodes we've gone through sort of the fine five main sort of sleep hygiene tips, and I'll just quickly go through them here because they're-- we've dealt with them before, which is regularity, going to bed at the same time, waking up at the same time, getting lots of darkness at night because we are a dark-deprived society. And I actually think I've done a bad job of describing to the public the importance of the opposite, which is making sure you get daylight during the first half of the day. I think that's just as important. Then temperature, we've spoken about that a little bit. You need to get cool to get to sleep, and it's the reason that you will always find it easier to fall asleep in a room that's too cold than too hot. You shouldn't stay in bed awake. That trains your brain to be triggered by your bed and force you awake because you have a learned association. So if you've been awake for 20 minutes, then get up, go and do something else, and only come back to bed when you're sleepy is the general rule. And then finally, you know, trying to avoid alcohol and caffeine in the afternoon and for alcohol in the evenings, as we've said. So those are the sort of typical tips. But I think if I were to add a few others, the other one that's absolutely critical that I probably haven't espoused enough is a wind-down routine. Because many people in society expect sleep to be like a light switch, that we should just jump into bed and it sh-- we should just turn off the light and the brain should do something similar and go straight into sleep. Sleep as a physiological process, if you study it, it's just not like that. Sleep is much more like trying to land a plane. It takes time to gradually descend down onto that hard foundation of this thing that we call a stable night of sleep. So give yourself some wind-down opportunity time. Build it into your routine. For some people it's 15 minutes, others it's 30 minutes. Light stretches, meditation, putting all of your phones and your gadgets away, staying clear of any inbound in the last 30 minutes. Whatever it takes, set it up and then maintain it, because if you have kids, you'll know all about this. You know, you have a routine for the kids, and you've got to try and stick to it, and if you break the routine, bad things usually happen with sleep. We're the same as adults. There's no difference. So I think that's the first thing I would say. The second probably tweak is if you are struggling with sleep, remove all clock faces from your bedroom. [laughs] It's not going to help you to know that it's now 2:35 a.m. in the morning and you've still not been able to fall asleep. It's only going to trigger more anxiety. And there's been a nice study here from UC Berkeley, not from my center, but from another sleep researcher, Allison Harvey, who looked at this in people who are poor sleepers with insomnia. Removing clock faces can certainly help. The next thing I would say is that try to keep, of course, all of your technology outside of the bedroom, and if you can, don't make it the first thing that you check in the morning. Because for most of us, the first thing that we do when we wake up is that we swipe right, and this flood of anxiety just washes onto us like a tsunami. And that's problematic, not just because it's a bad way to start your day, but because you train your brain in this Pavlovian way that every morning, as you're tucking yourself into bed at night, every morning, what's coming to you when you wake up is this jag of what we call anticipatory anxiety, and it lightens your sleep throughout the night because of that expectation. So try to avoid that. If you absolutely have to, and again, trying not to be puritanical, take your phone into the bedroom, one of the other problems is that it causes what we call sleep procrastination, which is that you're sitting there in bed, you've got your device, and you think, "Well, I'll just check Amazon and order that thing. I'll just check Facebook and I'll just, uh, I'll send that last email." And you look up and now it's 40 minutes later. The rule of thumb that a friend, a colleague of mine, Michael Gradner, said, I love this, if you're going to have your phone in your bedroom, the rule is that you can only use it if you're standing up And after standing up for about five or 10 minutes of phone use, you just think, "God, I'm-- I just wanna sit down. I just wanna get into bed." And at that point, the rule is you've gotta put your phone away. So those would be sort of three additional things that I would advise that can really help.
- PAPeter Attia
I like that a lot. I would actually add, just from a personal standpoint, I've, uh, maybe, maybe three months ago instituted a little policy for myself that I've really enjoyed, which is not looking at my phone for an hour when I wake up.
- MWDr. Matthew Walker
Yes.
- PAPeter Attia
Luckily, I don't sleep with my phone in my room, so that's not an issue. But it used to certainly be the first thing I'd go and grab when I got up. And if I get up at, you know, 5:00, I won't look at it 'til usually after 6:00 AM. And that's interesting. I didn't realize that the ef- the effect that that could have on my brain as I'm coming into consciousness, knowing that I'm not gonna be flooded with information, especially the type of information I don't like, which is generally all the information on my phone.
- MWDr. Matthew Walker
Yeah, I'll just stick two additional pins in that. The, the first is I think any- everyone has had this experience in the extreme, which is where you know you've got to wake up the next day for an interview, or you've got to wake up for a flight that you have to catch. You know for a fact that firstly, your sleep is going to be shallow. It's not going to be particularly deep, and secondly, you almost wake up two minutes before the alarm because you're that on edge. Well, imagine a diluted version of that, but every single day. That's what bringing your phone into the bedroom and opening it up first thing is all about. The second thing I would say is you're right, and set manageable goals. I really enjoy the work of a guy called BJ Fogg, who's a researcher at Stanford who looks at behavioral change, and it's all about incremental. So if you're trying to get someone to floss their teeth for the first time for dental hygiene, don't say, "Okay, here's how you floss. You need to floss before you go to bed." You say, "All you're allowed to do for the first week is floss your front two teeth, and you cannot do any more. That's it." And then we say, "Then to the next-- Then add two more teeth for the next week, and then two more." The same with sleep. If you are accustomed to doing this with your phone, which is so understandable for all of the pressures that we understand from society and, and social media, start by saying, "I'm gonna give myself five minutes. I'm gonna firstly not check my phone. I'm just gonna wake up, brush my teeth, and make whatever drink that I have in the morning, and when I sit down, that's when I am gifted the opportunity to look at my phone." And then try to push it to 10 minutes, and then try to see if you can get changed, have your shower, wash yourself up, whatever you do in the morning, and only then open up your phone. And keep pushing it longer and longer. Make it a manageable goal. Otherwise, don't set yourself up for failure. Do it for success.
- PAPeter Attia
Yeah, I think the, the same advice is great for something like meditation, where, you know, for many people saying, "Hey, why don't you commit to 20 minutes of meditation a day?" I mean, that's, it's almost impossible out of the gate. But if it's, "Hey, meditate every day," and if you do a three-minute meditation, that-- you know, you're better off doing three minutes a day than 20 minute once a week. Um, I think it's the same sort of idea, which I, which I agree. I think it becomes a lot easier.
- MWDr. Matthew Walker
The last thing I would say is that none of these tips that we've spoken about, which are typically sleep hygiene tips, are going to work if you actually have a sleep disorder. So the analogy here, again from a colleague, if I'm an athletic sports coach and I'm giving you all of these tips for improving your performance, but you've got a broken ankle, none of them are going to make any difference to your performance until we actually get you to a doctor and fix the broken ankle. It's the same with a sleep disorder. If you have, you know, insomnia or if you have sleep apnea, none of these things that I've been talking about are going to help you. If you suspect that you have either one of those, definitely go and see your doctor. See if you can get some kind of sleep intervention. [upbeat music]
- 59:32 – 1:08:32
The optimal room temperature and body temperature for the best sleep
- PAPeter Attia
Okay, let's shift on to temperature. We have a ton of questions on this, including one of my patients who has specifically asked me to ask you a bunch of questions on this. So I'm looking at all these questions, of which there are so many, and I wanna start at the top rather than-- So I'm gonna kinda mix up the order a little bit on these. And this question in particular I think is a great foray into the discussion. So the question is, did our ancestors get better quality sleep during certain times of the year and/or in certain climates? So for example, Death Valley in the summer, and I don't know how many of our ancestors were spending that much time there, hopefully not too many, but, um, presumably there are hot places, cold places, et cetera. So I think what this question is obviously getting at is there's a general belief that we sleep better when we're colder. There must have been a number of times when our ancestors were either in places that were not cold or in places where, at least during a season, it was warm. What can we infer or impute about sleep quality and temperature from that?
- MWDr. Matthew Walker
So the best data that we have right now, again, comes back to some of these hunter-gatherer tribes. Some of them live at different latitudes, and the best data that we have are folks who are very close to the equator. And at that point you think, well, how is this going to answer the question? Well, temperature variation where they're at is still quite significant from summer to winter. It turns out it's just more about sort of, yes, rainy season and dry season, but the temperature does fluctuate by some degrees too, and you can look at other communities that are a little bit further out. But here's what we find. In the summer, typically, yes, they actually sleep less when it's hotter, which is going against what needs to happen to your core body temperature to get good sleep. It needs to drop, and it needs to get cold. During the hotter seasons, they typically sleep less at night, and then they seem to try and do some recovery by doing a short afternoon siesta. But when they switch over to the winter season where it's cooler, it's a little bit darker, but not that much, but it's really the temperature. When they get cooler, then they sleep longer at night, and the frequency with which they have daytime naps actually decreases. So I think that's the best evidence that we have right now from just sort of- Going back to basics, Homo sapiens, what was going on in terms of temperature? The seasons give us the experiment, and the data favors coldness for longer sleep.
- PAPeter Attia
When you now bring that question to a laboratory where presumably you can take -- and someone has done this, I'm sure, where they've taken subjects and basically developed the optimization curve of all things equal but temperature, there must be an optimization. There's probably temperatures at which you reduce latency, so it's easier to get to bed, but maybe temperatures where it's harder to stay asleep. For example, using myself as an example, I actually like to be really cold when I get in bed, and if I am, it might take me a little longer to fall asleep, a minute or two, but it almost guarantees I'll sleep in a more uninterrupted fashion throughout the evening. There are times when I get into bed, and this is again not true at home 'cause I can control the temperature in my home, I have more difficulty controlling it here, for example, like we're in Bakersfield. It's hot as Hades. The last two nights, and again, it could be the excitement of racing, but I also feel like I've been waking up a little warm, and I don't have my chili pad. I don't have that little cooling pad on my blanket. I've had no issues with latency, but I'm waking up early. So if you run through all the permutations and combinations of this, can one say there is an optimal room temperature or air temperature or skin temperature or something that we should be driving towards?
- MWDr. Matthew Walker
So right now, the data that we have is somewhere around about sixty-five to sixty-seven degrees is optimal for the sleep of most people. Now, there's going to be variability there for sure, and we know this. We can see this in the data too. But it's actually even a little bit more complex than that, and there have been studies that people have done where they almost strap you in what looks like a wetsuit, but it's got all of these veins that run throughout them, and we can percolate this water. I think we've spoken a little bit about this before, where you can exquisitely control the temperature, hot or cold, at any part of the body. And I'll summarize the findings as the following in terms of temperature. It's a three-part story. For your extremities, you need to warm up to cool down to fall asleep. Then you need to get cold to stay asleep, and then you need to warm up to wake up. And so the reason that you may be finding latency easier here, but quality of sleep thereafter worse, is because it's counterintuitive. How do I drop your core body temperature? I'm going to tell you I'm going to warm you up. But the reason is because if you take a hot bath or a shower, all of the blood is charmed to the surface of your skin, and it radiates the heat out of the core of your body. So in fact, your core body temperature plummets. It's the reason that hot bath is great, not because you're toasty in bed. It's 'cause your core body temperature is plummeting once you get out. So this is why sometimes having a cold room but socks on or a cold room with a hot water bottle at the end of your bed just to warm the feet, because it's the feet and the hands that need to get a little bit warm to bring the blood, because they are the best radiators of heat out of your body. So when we warm the paws of rats, for example, they fall asleep faster because you're charming the heat out of the core of the body. So the answer to the question really is a little bit more complex. Keep the room cool. Warm yourself up a little bit inside of bed to radiate that heat out and get you to sleep quicker. That will make the latency. You fall asleep faster, in other words. Then the ambient temperature will keep your body cold throughout that middle section and later section of sleep. And then if you have a sort of a smart thermostat, you can rise that temperature, I would say actually quite late in the game, in the, perhaps in the last twenty minutes or the last fifteen minutes, and that will try to rocket your temperature out and bring you... You will wake up easier and feel less groggy if that temperature is higher. Now, it's hard because the ambient may not necessarily change much of what's going on under the covers, but it's the reason that most people, when they wake up, they would like a hot drink, even sometimes in the summer, because the hot drink, for the most part, some people are just using caffeine, and that's what they think keeps them awake, but some of that benefit of the caffeine is actually not caffeine. It's just the hot drink itself that is helping bring back up the core body temperature that makes you feel more awake.
- PAPeter Attia
So can we quantify the following? Someone comes to you, and they say, "Matt, I'm doing all of these things off my checklist, but currently I sleep at a room temperature of seventy-five degrees." How much better would you predict I would sleep if my room temperature went from seventy-five to sixty-five?
- MWDr. Matthew Walker
So I think the hard part of this equation, and some people may face this too if they look at their data from sleep trackers, you're going to be sleeping better. We know it. This is using population statistics for an individual, so this is always dangerous, and I never want to sort of fall into that fallacy, but let's, let's go with it. On average, people are more likely to sleep considerably better at sixty-five than seventy-five.
- PAPeter Attia
Do you say that in terms of duration or stage quality or what metric?
- MWDr. Matthew Walker
So that's where the devil is in the details because some people will see it in terms of quantity, particularly the quantity of deep sleep. So when we do these studies, that's where you see some of the greatest benefits for the cooling down throughout the night. That's where sort of the thermal gradient can be beneficial. But what's not told is that the largest effect size is not really in quantity, which is minutes, which is what your sleep tracker, your wristwatch, or your ring will tell you, and you have to be very careful to judge the efficacy of that experimental change on the basis of quantity in minutes. Because if anything, when you look at the data, where you really see the effect is less so in minutes, which is quantity- Instead, it's in quality, which is measured by the electrical brainwave signature. Now, your wristwatch or your ring is not going to be giving you that detail. So if you assume that the drop in temperature has given you a nominal percentage benefit in terms of your deep sleep time, and therefore you don't think it's worthwhile, I think you may want to sort of just second check that logic because there we're seeing it's qualitative that's more beneficial. And you as an individual, it's very difficult for you to sense that qualitative change 'cause you're non-conscious, of course, and there's no good trackers out there right now that you can wear typically on your periphery that will tell you that metric. [upbeat music]
- 1:08:32 – 1:14:54
Blue light: how Matt shifted his thinking
- MWDr. Matthew Walker
So with that said, it's not necessarily that hard of a question because I'm constantly trying to run these calculations about all of my scientific sleep beliefs and think about these three buckets. I think the thing that I've probably changed my mind on most or had a reversal on is the effects of blue light on our sleep. And in fact, in the book, I spoke about a study at the time that had been done out of Harvard, which I still think is valid, where they'd used an iPad where you read on an iPad for an hour versus you read a book under dim light, and they showed that that iPad had this detrimental effect on sleep. It had delayed the release of melatonin. It had caused a reduction in REM sleep. And even when they stopped reading the iPad, it had a blast radius to it where the sleep quality was still bad for a couple of days afterwards. And it was a compelling study and published in a good journal. But over the years, I think there's been some research that's pushed back on that, and there's been some great work from a university in Australia called Flinders University, and Michael Gradisar has done some just great work on this at Flinders. He has changed my mind. I'm less bullish now about the idea that these devices that we use are sleep disruptive because of the blue light. I still think that has an effect, but what I think he's shown in some elegant work is that it's less about the light. It's more about the fact that these devices are just so activating, that these devices are designed to trigger alertness and what we call physiological arousal in the brain. And in other words, what happens when we use these devices, the reason that they're so disruptive to our sleep, is less about their blue light. It's more the fact that we are masking our sleepiness with this overriding artificial activation from the devices. In other words, let's say that all of a sudden it's 10:00 PM and you think, "I'm wide awake. I'm on my computer. I'm working. I've got my phone next to me. I'm checking it. It's pinging. It's dinging." All of a sudden, all of the lights go out. There's a massive electromagnetic pulse that curses across your environment. It knocks out all of the devices. You've got no phone, no iPad, no electricity. I suspect that within about 15 or 20 minutes you'd start to feel sleepy, and it's not because of the blue light effects. It's the fact that you are, and you were all along, sleepy. But these devices, because they're so activating, was creating a competing force that hit the mute button on the sleepiness, and it activated you. So I've actually down-regulated my belief in the effects of blue light, and I've introduced this new mental framework regarding the effects of the invasion of technology into our evening lives and our bedrooms, and I'm much more now enamored with this idea that they are mentally stimulating rather than blue light emitting.
- PAPeter Attia
Forgive my ignorance for this question, but has the experiment not been done where you've taken groups of subjects and you've subjected one group to just a blue light, so an actual blue light that's hitting, I forget how many nanometers that is, but the actual-
- MWDr. Matthew Walker
Right, in the shorter that wavelength. Yeah
- PAPeter Attia
... Yeah. And then you have another group that is just being blasted with red light, and then you have another group that is just being blasted with a regular LED and white light. So you're getting the same intensity of light, but you're moving the wavelength, and therefore you're nullifying the stimulatory effect of what's being read or looked at. I mean, to me, that experiment would eloquently demonstrate whether or not blue light per se is the problem. Has that not been done?
- MWDr. Matthew Walker
It has. So people have played around with the wavelength of the light, and what we believed is that it's the cooler blues, the shorter wavelength light, that are most detrimental. And the reason that screens were blamed is because they are LED based, which is enriched in the lower visible light spectrum, the shorter wavelength, in other words, the cool blues. And that's why the blame came because it was stamping the brakes on melatonin especially powerfully. And those studies were done. They were done by Chuck Czeisler and Steve Lockley from Harvard years ago, and that led to this sort of belief, and I still think there's good validity in that. And by the way, there was a couple of studies that came out in animals that were now suggesting, at least I think it was in rats or mice, I could be wrong, or if it was in fruit flies, I apologize, where they actually found the opposite, where they found that the warmer color lights had stronger blocking effects on melatonin. It began this sort of controversy, had we got it wrong about blue light? And then this work from Flinders University from Michael was coming online regarding this cognitive component, and it really sort of made me shift my belief system. So yes, those studies have been done, and they principally looked at melatonin. I think they studied less a full night of sleep with polysomnography and really asked the downstream consequences. They were just simply saying, how does it affect your melatonin, which is maybe one step short of saying, how does it then affect, as a consequence of that change in melatonin, your subsequent sleep? Without necessarily doing a much more sophisticated study, which I think are now being done, where you do the Coke Pepsi challenge of same amount of light stimulation. So light is standardized
- PAPeter Attia
Right. Light becomes the variable that's the only independent variable.
- MWDr. Matthew Walker
That's right.
- PAPeter Attia
And then you start measuring independent variable at polysom and melatonin for what it's worth, and do everything.
- MWDr. Matthew Walker
And then you do a second round of studies where light actually becomes the constant stimulus, where you maintain the same light exposure, but in one condition you're doing something cognitively activating, like building a Facebook account or checking that, versus you're simply just there in front of the blue light, but there's no cognitive stimulation to really do the two by two disambiguation of that. I think those studies are coming, but that's one of the things where I've definitely changed my mind, I think, and I felt compelled to now speak more about that and less about the blue light.
- PAPeter Attia
[Instrumental music]
- 1:14:54 – 1:19:52
Caffeine: how Matt has adjusted his hypothesis
- PAPeter Attia
The last set of clips will shift our focus to look at the effect that caffeine can have on our sleep and the dangers of sleeping pills. If you found yourself enjoying these clips and want more content, we have seven episodes with Matt, including three AMAs. These are great pieces of content to go back to and listen to if you want to scratch this itch a little bit more.
- MWDr. Matthew Walker
[Instrumental music] The other place where I think I've changed my mind and maybe even some of my behavior is around coffee and caffeine [laughs] . The evidence has continued to mount and it's unignorable. And now again, these are mostly associational epidemiological studies, which both you and I know are problematic for lots of different reasons. But they're so consistent that if you look at coffee drinkers, they reliably de-risk a whole constellation of diseases that you want to avoid. And yes, there is a dose dependency to it where once you get past kind of like three or four cups, then things go in bad directions or the opposite direction at least. But for the most part, there seems to be this set of very clear associations between low to moderate caffeine consumption and de-risking health disease conditions. How on earth does this square with Matt Walker's espousing of caffeine's impact on sleep and the fact that a lack of sleep seems to be associated with many of those same conditions? The go-between here is that caffeine, of course, can disrupt your sleep. So I've kind of modified my beliefs a little bit. I think caffeine consumption is actually not only just fine, but maybe to be encouraged if there is more causal evidence. I think you and Tim Ferriss would speak about this idea that the dose makes the poison, and that is true with caffeine, but I also think there's a second variable here. The dose and the timing make the poison when it comes to caffeine. If you're drinking it later in the day, then I don't think we would see those same health benefits. We would see health detriments, and we don't have the data to help to find that. But then I've added a layer of complexity to that after listening to a good friend of mine and a writer here in Berkeley, Michael Pollan, who wrote a book on Audible that you can hear called Caffeine. And it goes into great depths, and we spoke about this. He interviewed me for the book. He believes that the health benefits, which are very hard to deny of caffeine, are not really due to a cup of coffee. It's actually the fact that the coffee bean itself carries with it lots of antioxidants. And in fact, the reason that you get these health benefits is because the antioxidants take a joy ride on the good bus of this thing called caffeine. And his belief is that for Americans, for many Americans who don't get a balanced diet, coffee in the morning may be one of their only primary sources of antioxidant consumption, and that's why you see the health associations. And in fact, I looked at a fantastic review from two thousand seventeen, and what they found was that in fact decaffeinated coffee, which carries the same antioxidant load but without the caffeine, has many health benefit associations with it, which then started to make it all a bit more nuanced that perhaps it's more about the antioxidant benefit rather than necessarily the caffeine benefit. But there is certainly an association with coffee that I think makes me more likely to tell people, "It's fine to be drinking a couple of cups of coffee in the morning. Please do that." In fact, if anything, there seems to be some health benefits. I think it's probably because of the antioxidant benefits. But I've changed my mind there too. I think I've become more relaxed and in fact, I've now started to drink decaffeinated coffee in the mornings [laughs] .
- PAPeter Attia
And is the reason you're not drinking caffeinated coffee because it just activates you too much or because you still fear it will, and because you fear it will impact your sleep negatively?
- MWDr. Matthew Walker
Yeah, it's because I still fear that it impacts my sleep negatively. There was a study by a good colleague of mine at the University of Surrey in England called Derk-Jan Dijk, published many years ago, and they were actually dosing people with caffeine at 7:00 in the morning, and they could still pick up in the signal of subsequent deep electrical sleep that following night, a reduction in the quality of that deep sleep. So I think again, it depends on who you are. There are genetic differences in how quickly people metabolize caffeine, and I think I'm someone who may be on the moderate end of the sensitivity spectrum, so I typically stay away from it. But other people, I think probably don't have that same sensitivity in morning coffee consumption. Caffeine is fine.
- PAPeter Attia
[upbeat music]
- 1:19:52 – 1:37:11
The dangers of sleeping pills, useful alternatives, and cognitive behavioral therapy for insomnia
- PAPeter Attia
Well, thank you, Orrin Hatch, for the supplement industry. We owe you a debt of gratitude, and I hope you can hear the sarcasm in my voice.
- MWDr. Matthew Walker
[laughs]
- PAPeter Attia
I think most people now are wise to it, and we certainly spoke about it at length in the original episodes about the real downside of things like Ambien, Lunesta, these drugs. In fact, very recently, I just saw something in the news that tried to tally up the number of deaths that could actually be attributed to these things. So, I mean, I feel very comfortable telling patients that I would rather you stick your genitals in a grinder-
- MWDr. Matthew Walker
[laughs]
- PAPeter Attia
... than you take Ambien or Lunesta.
- MWDr. Matthew Walker
There's always the point in taping a podcast with Peter Attia where it just comes to one of these wonderful crescendos, the things that I think about but I have no bravery to say, and he just comes out and says them. And this is part of the reason I adore him as a, as a friend and colleague.
- PAPeter Attia
Yeah, I really hate these drugs. I really hate them. By full disclosure, I still prescribe them on occasion to patients who really insist on having them as a safety net. I would not let any patient have those, and I can monitor by prescription. There's no patient I'm gonna let take those drugs every night, and maybe if they need it a couple of nights a month as they're traveling and such, we work really hard to get them off it. But-
- MWDr. Matthew Walker
Yeah
- PAPeter Attia
... but let's talk about sort of the softer things that people often rely on consistently for sleep aids. What about things like Benadryl or Advil PM? I get a lot of questions about that here. I don't think we would argue that those are good for sleep. I think that maybe we could frame the question as how bad are they for sleep?
- MWDr. Matthew Walker
Yeah. So firstly, to come back to Ambien and sort of its collection, Lunesta, all of those classic what we call the sedative hypnotics. In fact, you're right. I think it was nine days ago from the point that we're speaking right now, the FDA updated its mortality risk warnings regarding those sleeping pills because of this increased risk of death, both acutely for a number of reasons, but also this data just chronically in terms of elevated risk of-
- PAPeter Attia
I think the chronic death is far greater
- MWDr. Matthew Walker
Right. Cancer, we also see in part, I think it's probably because of a weakening of the immune system, and I think we spoke about this before. The irony is that sleep is incredibly powerful in boosting the whole collection of weaponry in your immune system. Yet when you sleep and sleep long with those sleeping pills, you would imagine your immune system gets even better. The opposite seems to be true. It gets worse. And the, the reason we know this is because there's higher rates of infection in those patients who are taking sleeping pills, scales with the degree of use and dosage. So I would say trying to use those as a very last resort. Now, there are some patients for whom alternatives don't seem to work, and for a short period of time, that seems to be recommended right now by the medical community. But I should also note that in 2016, the American College of Physicians made a landmark recommendation that they said based on the health risks and the concerns together with the nominal benefit of those sleeping pills above and beyond placebo, sleeping pills must no longer be the first-line recommendation for insomnia. It has to be something else called cognitive behavioral therapy for insomnia or CBTI, which we can come back to in a second.
- PAPeter Attia
Which I've had three patients go through formal CBTI with great success.
- MWDr. Matthew Walker
It's a non-pharmacological, it's a psychological method. You work with a therapist, and they try to understand where your sleep problems are at and create a bespoke solution for you, the individual. So there's lots of tools in the CBTI box that we can use to try and help people sleep better, and because everyone who has sleep problems is usually a little different from one person to the next, you have to create a more Savile Row tailored suit for that person in terms of that sleep prescription, quote, unquote. But it's just as efficacious as sleeping pills in the short term. But what's better is that when you stop working with your therapist, those benefits can last now, I think the last report was maybe somewhere between up to five years that you can maintain that benefit, unlike sleeping pills, where when you stop them, you not only go back to the bad sleep that you had, it's usually even worse. It's called sleep rebound insomnia.
- PAPeter Attia
How do you recommend people find good CBTI therapists? Because like all things therapy-wise, the practitioner matters. Now, I've been very fortunate because we work with this amazing sleep doc named Vic Jain in Chicago, and wherever my patients are, if it's San Francisco, New York, he knows the best therapist, and he just makes that introduction, plugs us directly in. But if you're listening to this and you're thinking, "I live in St. Louis, and boy, would I really benefit from this," how can a person listening figure out is it just trial and error? You just have to go through people until you find someone who's really clicking with you.
- MWDr. Matthew Walker
So one of the things that we can do maybe in post in the show notes, there is a website that comes out of the American Academy of Sleep Medicine, and there is one page. It's not that easy to find, but I know the link, so I'll send it out. And you go to that link, and you insert your zip code into this website. So this is, of course, just for people in America, and it will return the closest certified centers by the American Academy of Sleep Medicine for sleep disorders, including CBTI, and you can give it a radius, and you can give it a distance. Tell me where it's close, and they will give you the sleep centers to contact. Contact them, and you can go from there.
- PAPeter Attia
And what should you look for in terms of-- 'cause we know that all doctors are not created equal, all mechanics are not created equal, all lawyers are not created equal. How does a person evaluate their own individual, or is it simply through the results?
- MWDr. Matthew Walker
I mean, right now it's going to be in part trial and error. And I would say have a conversation with two or three potential CBTI therapists and just try them on for size and see how they work. If you can get any referrals right now, sometimes you can even go onto places like Yelp or other places where you can get some reviews, too. Some people, if they're motivated to write, it's usually because they had a bad experience, so keep that bias in mind. But I would say if you can get a referral from a friend or a colleague, that's a fantastic way to go, too. And then speak to these people and ask them about their success rates and ask them also, "Where have you found problems with your patients? Which patients have you typically had the hardest difficulty with in terms of their profile of sleep problems?" And if they sound like you, then maybe you want to look elsewhere as well. But CBTI over sleeping pills for sure. In terms of things like Tylenol PM or-
- PAPeter Attia
Benadryl is... Yes
- MWDr. Matthew Walker
... Benadryl is typically used. There is a little bit of evidence that Benadryl-induced sleep also has some of the risks associated with it that sleeping pills have. It's less potent in terms of that bad consequence and outcome to sleep, but the bad consequence and outcome remains statistically significant in those reports. So I would shy away from things like Benadryl as well. Tylenol PM, I just don't think there's good enough data yet to suggest that it's either good or bad.
- PAPeter Attia
And what about low doses or intermittent use of benzodiazepines, either short-acting ones like Ativan or longer-acting ones, Xanax, or longer-acting ones like Valium? I talk about this in my jet lag protocol when I'm doing heroic bursts of jet lag, you know, 12-hour time zone difference, and I have to put myself to sleep. We talked about the entire routine around exercise and caffeine and going to sleep immediately, getting on the plane, and I use phosphatidylserine, and I use the Kirk Parsley stuff, and I'll also use Valium to just make sure I am out. And what are your thoughts on the short-term use of benzos, again, paired with these other agents around jet lag? I don't think anyone's really advocating they be used in any ongoing manner either.
- MWDr. Matthew Walker
Certainly not, yeah. Infrequent use, I suppose it depends on how infrequent. In one of the studies by a guy called Dan Kripke, who is actually emeritus here in San Diego, he just looked at not only whether use of sleeping pills was detrimental to mortality, he looked at the frequency of how often you were taking those. And what he was finding is that even anywhere between three to 18 pills per year carried a statistically significant increase in mortality risk for-
- PAPeter Attia
And did he put benzos in the same category as the Ativan, Lunestas?
- MWDr. Matthew Walker
He did, yeah. So he sort of has broken some of that stuff down and broken it out, too. I would say, in truth, see how far you can really get with all of the other kaleidoscope of possibilities of sleep-enhancing possibilities that we've discussed. And if those fail, then I think you can think about last resources. But those drugs typically just are not producing natural sleep, so I would think of those medications like that box on the wall that says, "Break glass in terms of emergency." If you're in that situation and you're really struggling, then it's possible that that's the time to break the glass. But those shattered shards can sometimes still-
- PAPeter Attia
They can still cut you. What about GHB or Xyrem-
- MWDr. Matthew Walker
Xyrem, yeah
- PAPeter Attia
... as a precursor? This is a drug that is incredibly potent in patients with narcolepsy. Xyrem is available by prescription. Of course, unless you have narcolepsy, you're going to pay an unbelievable amount. It's, it's one of the funniest sort of [chuckles] economic incentives imaginable. But several listeners have asked, and several of my patients actually have asked about does Xyrem actually produce appropriate sleep staging. What's the data on that?
- MWDr. Matthew Walker
So the data, if you look at it, almost looks like Xyrem is a great drug or GHB is a great drug for increasing the amount of deep sleep that you have, mostly because it puts your brain into a more sort of sedated slow rhythm, which a sleep technician, if they didn't know that you were on Xyrem, would look at it and say, "That looks not dissimilar to deep slow-wave sleep, so I'm going to score it as I'm sort of scoring these eight-hour sleep records. I'm going to score it as deep sleep." So overall, in terms of total amount of sleep, GHB or Xyrem does seem to actually increase the amount of slow-wave sleep time that is scored by a technician. And I'm being very technical in my language because I want to be precise in this regard. However, if you look at the electrical signature of that sleep, which is now independent of-- So when a sleep technician scores a trace, they have a set of criteria that they use to define which stage of sleep each 30-second epoch of time, each 30-second window of time there is throughout that eight-hour period, and they scroll through a 30-second page by 30 seconds, and they score each of those. They add them all up. That's what gives your sleep profile and sleep score. So using the criteria that we've had now for about 60 or 70 years, they will score more of your sleep as being, quote-unquote, "slow-wave sleep" when you are on GHB because it seems to produce what looks like slow brainwave activity, and by that criteria, they have to score it as such. But if you unbuckle yourself from this kind of standard sleep scoring criteria and a human and you just let an algorithm process the electrical signature of that sleep, it now does not look like naturalistic sleep. And in fact, if there's anything that we've seen that Xyrem seems to be detrimental to, it's actually these things called sleep spindles. Now, sleep spindles are these short synchronous bursts of electrical activity that happen during non-REM sleep. They last for about a minute or a minute and a half. And we know from the work that we've done and other people have done They are critical for things like learning, memory, and brain plasticity. And what we found is that when you take GHB or Xyrem, the amount of sleep spindle activity is decreased often.
- PAPeter Attia
This shows up sort of at the end of as you're transitioning from theta to delta. Does this typically occur-
- MWDr. Matthew Walker
It actually-- what happens is you usually see sleep spindles at the end of a deep slow wave. So you've got all of these slow waves that happen during deep non-REM sleep, and typically what happens is that sort of once you've hit the peak of that slow wave, you will often have a little bit of a spindle burst. And in fact, those two things couple. It's called phase amplitude coupling. So at the peak of the deep slow wave on its awesome rise up-
Episode duration: 1:37:11
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