Sleep is the Boss of You – Matthew Walker, Ph D

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You're listening to Bulletproof Radio with Dave Asprey. Today's cool fact of the day is that depriving yourself of sleep probably makes you older. It turns out that one night of partial sleep deprivation activates genes that that are related to biological aging in older adults, according to research from ucla. And the researchers said participants blood showed signs of deterioration in the cell's growth and division cycle after just one night of crappy partial sleep. And this is cool. A lot of the science that they talk about, especially in the US Government's garbage nutritional recommendations are basically correlations. Oh, we notice when people do this. But this research is different because it was causal. And the researchers the findings link sleep deprivation to the molecular processes associated with biological aging. And they use the word cause in that instead of correlate. And they're saying insufficient sleep can increase risk of chronic disease by basically making you old. That said, sufficient sleep and sleep deprivation are very much out there as what does that actually mean? If you get awesome sleep for seven hours, is it better than crappy sleep for nine hours? The jury's out. Although clearly if you've been listening for a while, you know my perspective on that stuff. Today's show is going to be pretty incredible because as you probably guessed by now, we're going to be talking about sleep and this is an area of huge passion for me. If you read Headstrong, if you are about to read my new book Superhuman, that you can pre order now on Amazon if you want to do that, you'll learn about sleep and aging and how I've gone from hating sleep and restricting myself to four or five hours a night for a while when I was starting Bulletproof just because it was in the way, to now happily getting six hours but getting as much deep in REM sleep as a 20 year old, you'll know that this is one of the areas of hacking. My wife puts up with me sleeping with EEG headbands on just to see what's going on in there. But we're going to go deep with a guy who calls himself the Sleep Diplomat and a professor of neuroscience and psychology at UC Berkeley, director of the center for Human Sleep Science and the lead sleep scientist at Google. Guy's been on 60 Minutes, National Geographic, Nova, NPR, BBC, and author of the international best selling book why We Unlocking the Power of Sleep and Dreams, which has sold a million copies worldwide in 34 different languages. In other words, that book kicked the Bulletproof Diet's ass, which is about half as many languages and half as many copies. So welcome to the show. Matt Walker, Dave, It's a pleasure to.

Be here and thank you so much for having me.

I wanted to have you on because you said something that was sort of in your face. You said, we're in the midst of a catastrophic sleep loss epidemic. What does that mean?

There is a global sleep loss epidemic underway. What we know is that within the space of probably less than 100 years, which is obviously a blink of an evol eyelid, we've lopped off somewhere between 15 to 20% of our sleep amount. So if you look at surveys back in the 1940s, the average American adult at least was sleeping 7.9 hours a night. Now that number is closer to an average of six and a half hours a night. And that's the average, which means that there's a large part of the distribution that's actually well below that average. And so if you were to think about saying, you know, in the past 20 years, by way of a restricting device around your neck, you've reduced your blood oxygen saturation by 20%, you're down to 80%, you know, that would be astonishing. But that's exactly what has happened with sleep. And we see that same profile in most developed nations. You know, my home country, the United Kingdom, is not much better. 6 hours and 49 minutes. Japan is worst, it's 6 hours and 22 minutes now. So that is, that's a decimation of sleep that's happened throughout the industrial world within, you know, less than 100 years.

Well, we're going to have to get right into an area where we might disagree and not really sure yet. How do you know that that isn't enough sleep? I mean, there is that big study of 1.2 million people showing that people who sleep eight hours a night die more of all causes than people who sleep six and a half hours a night.

So what we find is that the less and less that you sleep, the higher and higher your mortality risk and the higher your risk for most of the diseases that are killing us in the developed world. There is actually though, a very interesting curve to that mortality risk. And you're right that once you get actually above nine hours of sleep, your mortality risk then increases significantly. So it's not a U shaped function, it's more like. It's more like a J shape function, kind of a J turned backwards, as it were. So in other words, mortality risk on the vertical, less and less sleep as you go to the left the higher and higher your likelihood of dying is. But once you get past about eight and a half to nine hours, there is a hook up in the mortality risk. And at first it seems like perhaps that's telling us if you sleep too much, you're going to die at a younger age. However, I think the media has been misinformed. If you actually look at those studies, what seems to be happening is that that hook is caused by people who are very sick. And what we know. So these are people with usually infectious diseases or cancer. And what was happening there is that sleep is the best sort of health insurance policy and it's the best immune and healing process that we know of. And when you are sick, I think everyone knows, you just want to curl up, get into bed and sleep it off, essentially. And sleep, we know, actually responds to infection. It's a very well replicated finding. What was happening here, we now believe, is that those people were so sick and their bodies and brains were calling up more sleep to help the fight against the disease, but the disease was just too much for sleep. So it artificially looks like sleeping more is bad for you, but that does not seem to be the case.

All right, I love that answer. To put it in one sentence, basically, sick people need more sleep.

That's right. Sick people sleep more and they need more sleep. But I do want to actually almost come over to your side, and this may be strange coming from a sleep scientist. Let's just go a little bit further with a thought experiment though. Could there be a thing as too much sleep? I actually think yes, there could be. And the reason I believe that is because it's no different for any of the other three critical ingredients of life. Food, water, and oxygen. So can you overeat? Yes, you can. Can you actually get too much oxygen? Yes, it's called hyperoxemia and it will cause free radical damage to brain cells. Can you over hydrate? It happened in the 1990s with the ecstasy craze where governments were saying, when you go to the dance clubs, please drink water. People drank too much, their blood pressure went up, and cardiovascular events. So in all of these things there is a sweet spot and getting too little and too much seems to be a problem. Are most people in danger of getting too much sleep? Au contraire would be my response.

Okay, full agreement with you there. I knew we were going to find some common ground here, but there's kind of the opposite side of the coin here. If sick people need more sleep, wouldn't it follow that exceptionally healthy people need less sleep.

If sleep was only there to actually, for example, support your immune system, you could imagine that would be the case. But it's not. There is no single major system within the body. Reproductive system, cardiovascular, thermoregulatory, metabolic, or upstairs in the brain in terms of a neural process. There is no single system of the body or the brain that isn't optimally enhanced by sleep when you get it, or detrimentally impaired when you don't get enough. So sleep actually services every one of the biological operations that we know of in the brain and the body. And so therefore, just because your sort of, let's say your immune health is good doesn't mean that your cardiovascular system doesn't also need sufficient sleep or your reproductive system doesn't need sleep, or your brain and your neural processes, particularly in fighting things like Alzheimer's disease, doesn't need sleep. So that's why, just because you're healthy, you don't necessarily need less sleep. In fact, it's a very quick and easy way to get unhealthy.

Okay, I totally buy that. Now, if someone were to sleep six hours, say in an airport versus six hours in a cave, what's the difference between those two nights?

It's more than likely that there will be a difference in what we call sleep quality. So what you've done there elegantly is lock in quantity, which is where we're saying, look, clocked time is the same between those two conditions. When you're sleeping in a noisy environment or in unfamiliar environment, your sleep isn't the same with light. Quality. Yeah. And what do we mean by quality? Part of it is about how continuous your sleep is. Is your sleep broken up by brief awakenings throughout the night that usually results in poor outcomes the following day that we can measure in brain and body. The other aspect of that is let's say that you're not waking up anymore, but the depth of that sleep is not going to be as deep. So you're not going to get as much deep sleep. And you're also probably not going to get as much REM sleep. And I think REM sleep has been the neglected sort of stepsister in the sleep conversation. A lot of people say, I'm just going to focus on my deep sleep numbers. That's probably not the best way to do it for two reasons. Firstly, REM sleep is actually more important, we believe, for your mortality. And the reason is this. Back in the 1980s, there were some studies that will probably never be replicated because of ethical issues where they sleep Deprived rats until they died. And they had three main groups. One group was totally sleep deprived, and those rats basically died as quickly from total sleep deprivation as they would from food deprivation. So sleep is just as important as food. What was interesting is the other two groups. One of those groups was selectively deprived of non REM sleep or that sort of, especially that deep sleep. And the other was deprived of exclusively REM sleep, rapid eye movement sleep or dream sleep. What they found was that the rats died almost as quickly from selective REM sleep deprivation as they did from total deprivation, whereas non REM deprivation, which is that deep non REM sleep we were speaking about, the rats still died, but they just took about 60% longer to die. So in other words, if you want to kind of rank order the brutal priority of sleep and its stages on the basis of those studies, at least it's. It seems to be sleep in general, then REM sleep and then non REM sleep.

What percentage of your night, if you could sculpt the perfect night of sleep for you, what percentage of the night would you want to be? Light sleep versus REM sleep versus deep sleep.

So typically, what we see in the healthiest people, and I guess that's the best barometer, you would probably want to be seeing somewhere between 25 to 30% of the deep non REM sleep for REM sleep, somewhere between 20 to 25%. And I'm giving ranges here, so the numbers may not all add up, but it's an estimate. And then you want about 45 to 50% of lighter non REM sleep, which is what we call stage two, non REM sleep. And I should note that that other type of non REM sleep is actually critical. It's the most prolific stage of sleep that all of us experience, like non REM sleep. And you could well imagine thinking, well, that's just the stage that you have to go through to get down into deep non REM or to go through to get up into REM sleep. So it's kind of just junk sleep. It's quite the opposite. We're now finding that that type of sleep is packed full of things that we call sleep spindles, which are these short bursts of electrical activity that happen for about a second or a second and a half. And for example, those sleep spindles are essential for learning and memory functions. So, you know, it doesn't surprise me when I take a step back and we were to ask, well, which stage of sleep is more important? And the answer is they're all important because sleep is the most idiotic of all evolutionary behaviors for lots of reasons. And if Mother Nature could have excised any one of them because it was functional, functioned less, I well imagine she would have done that thousands, if not millions of years ago. But the fact that all of these sleep stages have fought their way heroically through every step along the evolutionary path must mean that all of them have a unique and important contribution to make. And that's exactly what we're discovering.

There's also the argument that Mother Nature didn't really evolve us to live in the world where we got all the food we need and tigers aren't really going to kill us. So some of those sleep things that evolved over all this time for the world we lived in might not be as relevant for where we are today. Do you think there's a possibility that in a world with just a different level and type of stress and a different amount of environmental control, nutrient availability, that sleep itself will change, maybe evolutionarily or maybe even consciously?

Yeah, it's a fascinating question, actually. Well, I'll come back to one thought about that. But I think sleep will evolve. Certainly what we know. If you look back across the millennia, we obviously emerged from apes, and there was something fundamental about the transition from tree to ground that happened. That when we as hominids essentially came out of the trees and onto the ground, the amount of REM sleep that we had shot up dramatically. And in fact, we are unique in the entire animal kingdom, or at least the mammalian kingdom. We have twice the amount of rapid eye movement sleep than any other species that we've measured. I make that point because it tells us that there were critical inflection moments during evolution where sleep changed for reasons that we still don't yet understand. There's some theories as to why. Will it change again? Undoubtedly. So will it be, you know, what is the time frame of that? I don't think we know. But what we do know right now is that from populations that we take in this present moment, in the current evolutionary state of our electrified society, when you take someone below seven hours of sleep, we can measure objective impairments in their brain and their body.

If you had to stack rank this sleep, let's say you're only going to get six hours of sleep because you're going to catch a flight tomorrow, or because you have screaming children, or all the reasons that people cite for not getting the amazing, perfect eight hours of sleep, even though they're all important, is it REM then deep, then stage two, non rem, is that the order of prioritization.

The inherent danger with that question is you have to ask what are you trying to optimize for? Because each one of those different stages supports unique and different functions. So let's say that you want to sort of optimize your glucose regulation. Well there the argument would be you should focus on deep slow wave sleep because that's been demonstrated causally to regulate blood sugar equilibrium. If you're trying to optimize for your learning and memory, then you may want to focus on lighter stage 2 non REM sleep as well as deep sleep because they have a combinatorial benefit. If you want to focus on your, for example, your emotional health and your mental state, then you may want to optimize for rapid eye movement sleep. So it really depends on exactly what your target is. And unfortunately as human beings you don't want to shortchange on any one of those. And you will pay the price no matter what.

I suppose the thing is you'll pay the price. But the average listener and there's hundreds of thousands of people listening right now, if they even track their sleep. And I've done a bunch of episodes on sleep tracking and I was just looking at my numbers for last night. I got an hour and 25 minutes of REM, an hour and 32 minutes of deep sleep in around 7 hours and 20 minutes. So not a great night's sleep for me just because the numbers are low and the amount of sleep I slept is high. Normally I'm six and a half, but I should be getting about two hours of each. And I'm listening to you about this non REM thing. But I'm going to be pragmatic. I'm looking at the ROI on sleep. What's the return on investment? So yeah, I could get two more hours of light sleep. Is it going to make me live 20% longer? Is it going to make me smarter tomorrow? Is it going to make me a better parent? What's it actually going to do for me versus where I could put that other two hours of time?

So actually all three of those examples sleep will support that you described, even the parental one. We know that and your relationship. In fact, sleep is predictive of marital difficulties, marital arguments and the quality of marriage too. So you can go from inside of the cell and we could speak about the DNA all the way up to high complex socio emotional functions, interpersonal relationships, and you can see that damage. So I think it really comes down to the question of, you know, what do you want out of life? Would you like to, you know, invite disease and sickness early into your life when you could be living a longer life, or are you happy to actually pay that cost towards the end of life and during your life, increase your risk of a significant morbidity, for example, like a heart attack, that you survive, but now you are compromised in terms of your heart function. So we know that there's probably, you know, if you were to try and ask me, stack diet, exercise, and sleep, because they're the other sort of two things that people try to optimize. You know, where does sleep sit in that? And we can play that game at a number of different levels. But let me just go to one extreme. Let's say I take you, Dave, and I deprive you of food for 24 hours, I deprive you of exercise for 24 hours, or I deprive you of sleep for one night, and then I assay your body and your brain across all of the different dimensions that are important for health. And yeah, and sleep just decimates those other two. I mean, it's not even close. Now, I'm not trying to belittle diet and exercise. They are fundamental and it's all interacting. Of course, none of these sit in isolation, but if you want a sort of a realization of what you're doing by under sleeping, I think that that's one good metric to keep in mind.

Okay, that is a beautiful example, and I'm glad you brought that up because that really paints it in a great context. And just for full disclosure, I started out 20 years ago pretty much hating sleep because it got in the way of all the cool stuff I wanted to do, right? And now I'm very conscious about using sleep as a tool. And I do things an hour or two before I go to bed that increase the quality of my sleep. And I generally wake up feeling really good. And my numbers make me happy to the point where I don't know that I would want to invest more of my life in sleep. But I also am doing stuff that is related to the Russians. And I want to ask you if you've ever looked at this, and if you haven't, we can just kind of move on. But back in the 60s and 70s, in the unique way that Russian scientists thought back then, they said, well, it's very expensive to send astronauts to space, and they spend a third of their time asleep. So let's just invent a technology so astronauts can sleep a lot less, and therefore we can spend less rocket fuel and build smaller rockets and send Less astronauts to space. Brilliant thinking. So they invented cerebral electrical stimulation. They ran a very small current back and forth between the ears at the same frequency as deep sleep or REM sleep, to put the brain in that state and probably do some weird electrical stuff, and found that they could function adequately, probably not perfectly, on two or three hours of sleep. And have you experimented with or seen the results of any kind of technology that purports to increase the effectiveness or efficiency of sleep?

There are a number of them. And by the way, those studies, they don't really assess the true whole organism. You know, they're usually assessing, you know, cognitive functions. So I think it's to be mindful of. But you have.

You have tumors, but your brain works.

That's right, yes.

They're not going to measure that.

Your systolic blood pressure just went from 120 to, you know, 165 within the space of eight hours. But don't worry, you're fine. So there are several things that people could do to try to augment their sleep and get better sleep in the mold that you're talking about. One is actually temperature. So it's mostly effective for deep sleep right now. But what we know is that your body needs to drop its core temperature by about 2, 2 and a half degrees Fahrenheit to initiate sleep and then to stay asleep. And it's the reason you will always find it easier to fall asleep in a room that's too cold than too hot, because too cold is taking you in that right temperature direction for good sleep. And there were some studies done, and we've played around with this, too, where you kind of essentially strap someone in what looks like a wetsuit that has all of these veins running all over it, these capillaries. And then you, as the experimenter, control the water flow in those capillaries. And you can warm the water up or you can cool it down, and you can do that to any part of the body discreetly. And what they were able to do is that by essentially warming the surface of the hands and the feet, they were able to charm the blood out of the core of the body. And therefore, your core body temperature plummeted as a result. And that increased deep sleep in young adults, but it even more dramatically increased deep sleep in older adults and those with insomnia. So temperature seems to be one of the ways that we can manipulate at least deep quality of sleep. If people are struggling with sleep, there's another technique called cognitive behavioral therapy for insomnia, or cbti. And that has really proven markedly efficacious. It's now no longer. The question is, does CBT help improve the quantity and quality of your sleep? The questions now in the research feel like we're doing. Is that sleep improvement actually improving other downstream sort of consequences? And there are now some great studies showing that it markedly improves your mental health. It decreases your paranoia, decreases anxiety, it decreases rates of depression. So there are a couple of methods that you can sort of, you know, some clinical, therapeutic, others environmental that you can play around with too. Light is another one of those things that we could speak about if you wanted to.

But yeah, Sachin Panda came on and talked a lot about light and biology. And one of my portfolio companies actually makes glasses that block all frequencies of light that affect the scn. And I think listeners could benefit from hearing you talk for just a brief period about how important light is for sleep. But I would just say go deep in the podcast with Satchin Panda or check out the TrueDark website for a bunch of research on that stuff. Just talk about light and what you've seen light does that's good or bad for sleep and just reiterate that for people who still turn their bright bathroom lights on at night.

So, yeah, Sachin is fantastic. We know each other very well, but we, we are a doc deprived society in this modern era. And it's not just about the devices, although I'll speak just very briefly about those that are harmful. It's also just that we bathe ourselves in electrical light throughout the evening. And the reason you need darkness at night is to release a hormone called melatonin. And melatonin helps the timing of your sleep and the healthy timing of your sleep. But technology is perhaps fast becoming one of the greatest sort of assaulting things in terms of our sleep. Once that he looked at the impact of one hour of iPad reading before bed versus just one hour of reading a normal book in dim light. And what they found is that the one hour of iPad reading actually blunted the amount of melatonin that was released by 50%. 5, 0. Furthermore, it delayed the peak of that melatonin, which normally should peak, you know, a few hours before bed and then rise nicely in the first couple of hours. It delayed that peak by three hours. So myself here in California right now, I would be much closer to Hawaii time if I read an hour on an iPad before bed in terms of my melatonin. Two other things that they found with that study. One is that it also decreased the amount of rapid eye movement sleep that people were having. And then finally, even when they stopped reading the iPad in the days afterwards, there was a blast radius impact of that reading, that the effect of on that sleep disruption didn't go away until two or three days later. Wow. So it's almost like sort of washing yourself out with a drug that, you know, just that one hour, you didn't shake it off for a couple of days. So light is something that I don't think we think enough about. And if you want a quick. I don't really like to call them hacks, but you know, when you, you know, blue light blocking glasses, there was one study that demonstrated some efficacy there for melatonin. The other way that you can do it is just turn down half of the lights in your house before you go to bed. You would be surprised at how soporific that that feels. And it really does make you sleepy. And then, you know, eye masks and sort of block out curtains throughout the night, if that's your thing.

It's ridiculous how much just dimmer switches can change your life. And you go to my house, there's dimmer switches on everything. We don't use white LED light bulbs. We use halogen bulbs because they dim better and they have a more natural spectrum that's less blue. And at night we have red nightlights or even red full on a few lamps. And all of my exterior lighting is red. So the difference in the quality of my sleeping, if I look at screens or whatever, I wear the glasses and the glasses from my company are they're red and they block violet and green and blue and other things for the melatonin effect. But I double my deep sleep on my sleep ring if I do that versus walk around the way I used to. So I found that between temperature, which I recommend, and light, as well as just not eating too close to bedtime. And then a couple supplements. The supplements for me help the rem, but for my deep sleep, it was all about just turning down the lights. But your studies show that it's actually affecting REM sleep, not deep sleep. What is the hack that raises REM sleep the most?

Other than lights, there's actually very few hacks for REM sleep. It turns out one of them may actually be that we're just exploring right now and we don't have enough data, is reverse engineering the deep sleep hack, which is if you look at the circadian profile throughout the night, and circadian just means your 24 hour biological rhythm, your core body temperature starts to go down before bed. It hits Its rock bottom core temperature around 3 or 4 in the morning. It stays there for about another hour and then it will start to rise back up in the late morning. Why is that important for rem? Well, your deep sleep and your REM sleep are not evenly distributed throughout the night. You have most of your deep sleep in the first half of the night and you have most of your REM sleep in the second half of the night. Especially in fact, in the last quarter of the night, which parenthetically, by the way, should give people pause. Because if you were to say, look, I normally get eight hours of sleep and I only got six hours last night, so I lost 25% of my normal sleep. I lost two hours from eight hours. 25%. That's true, but it's not quite true because yes, you lost 25% of your total sleep, but you may have lost 80 to 90% of your REM sleep. So there is a nasty twist in that tale of how sleep is distributed. And if you're shortchanging your brain by waking up early because you think you want to get a jump start on the day or get to the gym, you should be mindful of that science. And by the way, I may be sounding like I'm trying to tell people how to live. I'm not. I'm not here to tell anyone how to live. All I want to do is empower you with the science of sleep and then everyone can make their own informed choice. I'm not trying to suggest how to live here.

You're not coming across as that. But if you do this, then this will happen. That's sort of precious knowledge and that's the stuff that I'm working to tease out on every episode of the show. So I don't think that our audience is going to be offended at all by this.

I hope not.

I'm intrigued though, because the idea that wake up at 5:30 every morning to become a better human being, you're saying that that could kill your dreams and.

Probably yourself a little bit quicker or rather a lot more.

How Elrod is going to be so mad at you.

All I'm speaking are the scientific truths.

You know, I did wake up at 5am every morning for two years because I decided this is going way back. But I said, all right, this is what the strong people do. So I'm just going to make myself do it. And I found after two years I could do it. And I'm normally a very late, I stay up very late.