The Exchanges

Q to note is that Dr. Walker is not a medical doctor, and anything in here is just opinion. So before you do anything or make major changes to your sleep, Or your routines, it's wise to consult with your physician. It's time to listen and learn. Let's start with the basics. What is sleep? What are sleep stages? How do we sleep? How does it play out across the night?

A Yeah, sleep is a funny thing in that way. Um, sleep, at least in humans, and, um, in fact, in all mammalian species is broadly separated into two main types. Um, on the one hand, we have non-rapid eye movement sleep, or what we call non-REM sleep for short. Um, and non-REM sleep has been further subdivided into four separate stages, and they've been unimaginatively called stages one through four, um, increasing in their depth of sleep. So stages three and four, that's the really deep phase of non-repid eye movement sleep. And then stages one and two, that's what we consider to be light non-REM sleep. And then on the other side, we have rapid eye movement sleep or REM sleep, um, which is named not after the popular Michael Stipe, uh, 19 nineties indie pop band, but because of these bizarre horizontal shuttling eye movements that occur during the stage of sleep, uh, these rapid eye movements. And we're, by the way, we're yet to really understand why the eyes dart back and forward, left and right, left and right, during rapid eye movement sleep. But rapid eye movement sleep is principally the stage within which we dream. Now, that depends a little bit on your definition of dreaming. If you have a very lax definition, then you probably dream in almost all stages of sleep But when most of us say, oh, I had this strange dream last night, you're really talking about a dream that came …

AI assessment note: “non-REM sleep has been further subdivided into four separate stages”

Q prioritize the different types of sleep based on benefits to us? Like, is the REM sleep, which might comprise half of our total sort of sleep time, is that as valuable as what's happening in the first part of the night? Like, does the body have an evolutionary sort of, like, process by which it's like, okay, this is the most important type of sleep, we'll give you that first.

A That's a, it's a very astute question. Um, so, For most of us, we should spend probably about 20 to 25% of the night in REM sleep, about 20 to maybe 30% of the night in deep non-REM sleep, and the rest is light non-REM sleep. But people have asked that question to say, well, from an evolutionary standpoint, if deep non-REM sleep is biased in the first part of the night, and REM sleep comes in the second half of the night, does that mean that deep sleep is the best type of sleep, the most important type of sleep? And what we've discovered is that no one stage of sleep is more important than the other. Different stages of sleep do different things for your brain and your body at different times of the night. So when people come to me and they all say, look, how do I get more REM sleep? Or how do I get more deep sleep? I'll ask them, why do you want more of that deep sleep? And they'll say, well, isn't that the good stuff? Or they say the same thing about REM sleep. And it's actually not true. It's just that they all perform some different functions. And from an evolutionary standpoint, that makes a lot of sense. Why would mother nature lie you so vulnerable and unconscious if only one type of sleep was important? She would have excised the other type of sleep during the evolutionary course of development long ago. The fact that they still remain with us, all of them to this day, …

AI assessment note: “what we've discovered is that no one stage of sleep is more important than the other”

Q Everybody's got these devices these days, like Oura rings and stuff. Is there a danger to the quantified self movement? Do you think we're sort of like going too far by tracking everything, like heart rate when you're sleeping, and how long it took you to fall asleep, and your heart rate variability?

A Yes and no. I am, I'm a gadget freak, and I've worn, or I've placed on my body, I've stuffed up my nose, I've strapped on my head, I've jumped on mattresses, I've, I've done every sleep gadget that there is out there for the most part, um, And I do track my sleep. I track my sleep with an aura ring, and just to a full disclosure, I am, um, I am a scientific advisor to the company, um, and, and connected to the company, so take what I say about aura with a grain of salt, and I'm happy to sort of come on to, once we speak about whether sleep tracking is useful or not, What I would recommend in terms of sleep trackers and how I think about making the decision of which sleep tracker is the best sleep tracker. But I think there is a danger, and I don't think it's a danger for everyone, but I think for a, maybe a modest proportion of the population, I would say perhaps based on just my survey data, maybe around 10%, it could be as high as 10%, I think it's, it's potentially Damaging for a short period of time for that small 10% of the population, and it creates now a condition that we have a label for in sleep science, which is called orthosomnia. And ortho, you've, you know, everyone's heard of this in medicine, you know, orthodontics, orthopedics. What that means, it's, it's about straightening or getting something right. Um, so orthodontics, getting your teeth straight, orthopedic…

AI assessment note: “I think there is a danger... it creates now a condition... called orthosomnia.”

Q You mentioned temperature a while back. Is there a relationship to temperature and sleep? Uh, and does that change during the night during our four phases?

A Very much so. I think many of us underestimate Temperature as one of the key regulators of sleep, and I've got so many ways that I could, I could show you as to why temperature is so impactful for your sleep at night. For example, when we've studied hunter-gatherer tribes, whose way of life hasn't changed for thousands of years, and you study their sleep, one of the striking, one of the many striking things that we've learned about their sleep is that they don't go to bed at the moment when light disappears, When the sun is completely set, they go to bed usually a few hours after that, and they don't wake up with the rising of the sun. They usually wake up a little bit before that with the rising of temperature, and so it is temperature that seems to dictate when you want to fall asleep, and it's temperature that seems to dictate when you will naturally want to wake up, and we can do these studies. So for example, if I were to bring you into my sleep laboratory, um, and you come in, and you're in a room with no cues as to what time of day it is. There's no windows, um, There are no clocks on the wall, and I say to you, all I want you to do, and I'm going to check in with you every 30 minutes or so, I'm just going to say, are you feeling sleepy? Are you, do you think you're ready for bed? And, you know, just tell me, whenever that, that kind of wall of sleepiness hits you, and y…

AI assessment note: “Very much so. I think many of us underestimate Temperature as one of the key regulators”

Q Or it dictates your whole day, right? You get up and you see your sleep score, and then you're like, oh man, you know, I feel great, but now all of a sudden my sleep score says I'm only, you know, a 71, so the day's ruined.

A And what's very interesting about that is it's, It sounds like psychological hocus pocus, um, au contraire, and we've done some studies, and other people have done some studies, where you'll bring people in, and you'll have them sleep in the laboratory, and you'll have a group where, you know, they've slept, I don't know, seven and a half, eight hours of sleep, and you say, you know, before they do a whole set of psychological tests in the morning, which is often what we do after a night of sleep at my sleep center, You wake up and you'll say, look, would you like to know how you slept? I'll say, yeah, I'd love to know. And you say, well, you slept pretty well. Um, you've got a really healthy profile of sleep. You slept about seven and a half hours. Your sleep efficiency is, you know, sort of somewhere upwards of, uh, 90%. Everything looks great. And then for the other group, you will say, ah, you know what? I know you think that you slept well, but looking at our data, you really didn't sleep well at all. You had a really low sleep efficiency, and it looks like even though you probably weren't aware of it, you were awake for a lot of the night, even though they've had roughly the same amount of sleep as the other group.

AI assessment note: “It sounds like psychological hocus pocus, um, au contraire, and we've done some studies”

Q How do we know we're getting enough sleep? Aren't we all different? Like, has the amount of sleep we need changed across time? Does it change across even our life?

A I'll come back to the, how we know that we're getting enough sleep in a, in just a second. To your point though, on the second question, we are all different. There is a wonderful array, a wonderful variability in what we call sleep need across the population. So If you hear idiots like me saying, okay, you know, it's eight hours, um, that's, in some ways, that's sort of nonsense. What we recommend is somewhere between seven to nine hours will cover the vast majority, the vast distribution of human sleep need. And that's echoed not by just my, um, uh, inane British dulcet tones, but by the CDC. Um, they stipulate after reviewing the data a minimum of seven hours of sleep for the average adult. So we are all different, and there are people at the tail ends of that distribution. Which brings us on to probably the more important question, which is, you know, short sleep and, and how little sleep can I get away with? Um, What we found is that once you drop below seven hours of sleep, for most people, we can measure objective impairments in either your brain and your body. And, and I'll come back to that nuance because there is beautiful nuance nested in that. I should also note there are genetic short sleepers, and those genetic short sleepers seem to be able to get away and quote unquote survive with as little as six to six hours and 15 minutes of sleep, and they seem to perform n…

AI assessment note: “To your point though, on the second question, we are all different.”

Q it at night, is there like, I'm going to lose my job right here by the way. Is it, is there like a half-life to it in the same way that there was with caffeine? Is, is there something like, Hey, if you're going to have a couple of glasses of wine, like, uh, you know, maybe cut it off four hours before bedtime. Is there a heuristic around this?

A There's a little bit of heuristic and it's probably earlier in the day. So, you know, probably, you know, having a glass or two with lunch, uh, Is less likely to impact your sleep, but we found that even just one glass of wine in the evening can have, you know, significant and measurable, uh, impacts on your sleep at night, which, um, I know, I, all of this makes me, I'm, I'm desperately unpopular as a person, um, just, uh, firstly out there in the public, and secondly, even to my close social circles, um, based on personality and nationality. Um, but saying this type of stuff makes me even sort of, ah, less popular and, um, and interesting. So, but best to be truthful about the science.

AI assessment note: “There's a little bit of heuristic and it's probably earlier in the day.”

Q Yeah, I want to know what are the variables that you sort of keep track of, and what devices and tools do you use?

A So I use, um, right now my go-to device is the Oura Ring, and I should note, by the way, that I was using the Oura Ring for about two years before I joined the company, and it ended up being the only device that really stuck with me, and that's in part the That was one of the two reasons why I decided to help the company out. The second was just because of the team and the people there, that I had not met a team like that in the sleep, and I've been working, I've been working in the sleep tech industry and advising, consulting for, for, um, probably about 15 years, and that team was very special, and they've gone on to do amazing things, and they continue to do amazing things. So, That's the reason I went with them rather than some of the other sleep bands or sleep wristwatch devices out there. And the reason I like Oura Ring is because both of the data that it provides that some of these other companies don't, or they're only now catching up in terms of, of doing, but it's also the form factor. And the way I think about sleep trackers, if someone were to say to me, what's the best sleep tracker, I would say the best sleep tracker is the one that you use most frequently. The second way that I think about sleep trackers is, um, the accuracy, and I think looking at the data out there, and again, I'm probably more intimate with Aura than anything else, I think right now, and it's …

AI assessment note: “right now my go-to device is the Oura Ring”

Q Let's talk about the two most common stimulants, which are caffeine and alcohol, but let's, let's break them into two so we don't commingle them. How does caffeine interact with your sleep? And should I still drink coffee? Like you're scaring me here.

A So this is something that I think I've I very much changed my tune on when I first came out with the book and started to become a little bit more, um, public as a, um, a communicator of, of sleep's, um, story and my love affair with sleep. I was probably heavy handed in lots of things and, and wrongfully so. And caffeine was one of them. I sort of almost, you know, vilified caffeine. I've changed my tune firstly, because if you look at the data and It's very clear that drinking coffee is rather good for you. But here, when it comes to coffee, and when it comes to sleep, and when it comes to health, The dose and the timing make the poison. Just as an aside, by the way, the reason that coffee has those remarkable health benefits that it does, and in fact, paradoxically, the benefits that you get from drinking coffee are very similar to the benefits that you get from getting sufficient sleep, and people have said to me, how can you square that circle? How can you resolve that tension? It doesn't make sense from what you're saying. Well, the reason that coffee provides those health benefits is not because of the caffeine. It's because the coffee bean provides, for most people, because our diets are not really very good, the standard American diet, for example, um, isn't ideal in its nutritional profile. The coffee bean provides the majority of people's dose, daily dose, of things c…

AI assessment note: “when it comes to coffee, and when it comes to sleep... The dose and the timing make the poison.”

Q Is there a danger to trying to force more sleep? Like, what if you wake up in the morning naturally, and you're like, oh no, I only slept, you know, five hours, like, should I, and I can't go back to sleep, should I just lie there until like?

A That's a hard question to answer without sort of taking more of a clinical history, and by the way, just right up front, I am not a medical doctor, I'm not a clinician, uh, I'm just a scientist, and so I could say what the science would speak to on that point. If you are getting just five hours of sleep a night, Typically we would think about that being insufficient amounts of sleep. If you were to say, look, I'm getting six and a half hours of sleep, um, each and every night, and I feel well-rested during the day. I don't feel as though, and this is probably another way to ask the question, am I getting enough sleep? Do you feel as though you need caffeine to function in the morning? Because if you do, you're probably self-medicating a chronic Sleep debt. So if you can say to me, look, I wake up naturally. I've had six and a half hours of sleep. I don't feel sleepy during the day. I function perfectly fine. I don't drink caffeine. I don't need caffeine to function. Um, then I would say, okay.

AI assessment note: “and this is probably another way to ask the question, am I getting enough sleep?”

Q Let's switch subjects a little bit. Since you wrote the book, I mean, you faced a lot of controversy since you wrote the book, uh, Why We Sleep. What would you attribute that to?

A I don't know if it would be classified as, as a lot of controversy, but certainly there's been sort of some controversy. Um, and And I really, you know, I'm really welcoming of, of that, and if you were to ask sort of, you know, which parts of the different sort of critiques that have been sort of passed my way that I would agree with, the first thing I would note is that I've actually written an essay that is sort of on WordPress, and that really offers a very in-depth exploration of the varied questions, Um, that people have raised. It also details any errors that were present, and there were some, absolutely, there were some errors in the first edition of the book that have now been corrected in a second print of the book. I think the first point to make in all of this, and I've spent so much time thinking and journaling and sort of, sort of meditating on all of this, the first point to make is that if I'm ever wrong about something, Um, life in general, or science specifically, I don't want to be wrong any longer than I have to be. So that's the first issue. The second issue is actually one of reflected gratitude to the folks who took the time to actually reach out or to note on their blogs any errors that they found, um, in the first edition of the book. And, you know, no matter how they, those, those things were expressed, whether they They were, you know, somewhat hyperb…

AI assessment note: “if you were to ask sort of, you know, which parts of the different”