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The Definitive Guide To Sleep | Dr Greg Potter

Dr Greg Potter is a PhD graduate at the University of Leeds & Content Director at HumanOS. His research focus is on sleep and chronobiology; looking at circadian rhythms, light-dark cycles and the potential for meals to entrain peripheral circadian clocks. The unsung hero of health is hiding under our pillow every night and today we learn just how important a good night's sleep is to our short & long term fitness, our mood, cognitive output, physical performance, injury risk, weight and pretty much everything else. Discover the best approach for dealing with sleep deprivation, how to optimise your sleeping environment, how meal content & timing can affect our circadian rhythms and a lot more. Further Reading: Follow Greg on Twitter: https://twitter.com/gdmpotter $1 for 1 month of Premium Membership at: https://www.humanos.me/ (Code: modernwisdom) - Listen to all episodes online. Search "Modern Wisdom" on any Podcast App or click here: iTunes: https://itunes.apple.com/gb/podcast/modern-wisdom/id1347973549 Spotify: https://open.spotify.com/show/0XrOqvxlqQI6bmdYHuIVnr?si=iUpczE97SJqe1kNdYBipnw Stitcher: https://www.stitcher.com/podcast/modern-wisdom - I want to hear from you!! Get in touch in the comments below or head to... Twitter: https://www.twitter.com/chriswillx Instagram: https://www.instagram.com/chriswillx Email: modernwisdompodcast@gmail.com

Chris WilliamsonhostDr Greg Potterguest
Aug 27, 20182h 3mWatch on YouTube ↗

EVERY SPOKEN WORD

  1. 0:00 – 6:38

    Meet Dr. Greg Potter: sleep, diet, and metabolic health research

    1. CW

      (wind blowing) Hi, friends. How was your night's sleep? Was it good? Hopefully after today's episode, it's going to be better. Today, we're going to speak to Dr. Greg Potter, who is a PhD graduate from the University of Leeds, and a specialist in sleep. His work has been featured absolutely everywhere, from Reuters to Time Magazine, Washington Post, USA Today, Daily Telegraph, BBC Radio. He's, um, he's pretty prolific. Uh, and he's also the content director at HumanOS.me. Now, the guys at Human OS haven't sponsored this, uh, episode at all. However, it is a fantastic service that you should check out, and later on in the episode, Greg explains what it's all about. But if you do want to go and have a look, it's free to sign up, and with the code "modernwisdom," you can actually get their premium version for a dollar for the first month, and there's no minimum term. So, check it out. Now, many people take a lot of time researching their diet or their exercise and making sure that they're trying to live a healthy life. But quite a lot of us overlook just how important sleep is in this equation. And having read Matthew Walker's book, Why We Sleep, I was struck by just how little care I was giving to my sleep habits. The implications on your health, mood, and performance, both in the short and long term are pretty drastic, and I don't think that there can be enough weight applied to just how important sleep is. Now, hopefully today, we're gonna convert you from a nonbeliever to a sleep paragon who is armed with some new tools to improve their sleep and a passion to actually make it better. Essentially, what I'm saying is that if you live a long and healthy life with all of your faculties still intact, at the ripe old age of 95, you can be on your deathbed incredibly mobile and full of zen and look back at this podcast and think, "Thanks, Chris and Dr. Greg." (upbeat music) Dr. Greg Potter, welcome to Modern Wisdom.

    2. GP

      Thanks very much. It's great to be here.

    3. CW

      How are you today?

    4. GP

      Yeah, I'm very well. How are you?

    5. CW

      Uh, fantastic, thank you. Did you get a good night's sleep?

    6. GP

      Not bad. I've been up for a while.

    7. CW

      By- by whose standards did you have a not bad night's sleep?

    8. GP

      By my own not particularly good standards right now.

    9. CW

      (laughs) Rigorous sleep standards, right?

    10. GP

      Well, I don't set the bar too high, but the last few weeks have been a bit ropy at times.

    11. CW

      Is it do as I say, not as I do?

    12. GP

      Yeah, it's one of those. (laughs)

    13. CW

      (laughs) Um, so can you explain to the listeners what your speciality is, what your, um, what you focus on in your research area?

    14. GP

      Sure. So, I have just passed my PhD, which was-

    15. CW

      Congratulations.

    16. GP

      Thank you very much. Which was at the University of Leeds, and I'm in Leeds right now. And during my PhD, I focused on sleep, diet, and metabolic health in UK adults. So, I focused on studies of human beings, and in my PhD, there were several different parts. It began with the validation of a dietary recall method. So, if a nutritionist is interested in how diet affects health and risk of various diseases, then they need accurate ways of capturing what somebody eats. And to that end, you need to validate the tools that you use, and I was involved in the validation of one of those tools, which is called myFood24. And it's the first validated tool designed for use specifically with adults in the UK. It's very comprehensive, and that paper is just being published. And I then used that dataset to look at associations between when people eat relative to when they sleep and their metabolic health. I also did some work looking at how sleep duration is associated with risk markers that are associated with diabetes in the UK and also with how people eat. And then at the end of my PhD thesis, I did a randomized control trial of long-term melatonin supplementation among people who are at high risk for type two diabetes. So, let's say, for example, Chris, that your dad has type two diabetes. That would increase your susceptibility to that disease.

    17. CW

      Mm-hmm.

    18. GP

      Question was, can you use melatonin as a prophylactic agent against you developing type two diabetes? So, just wrapped all of that stuff up and now I work for Human OS as content director and have been working with those guys for about the last 18 months or so, and have more or less been working full time for the last four months.

    19. CW

      Mm-hmm.

    20. GP

      And the CEO also has a strong background in sleep research, so we share that in common, but we're very-

    21. CW

      You're in good, you're in good company then.

    22. GP

      Yeah, I would say so. For sure.

    23. CW

      That's fascinating. I mean, there's, there's an awful lot, (laughs) an awful lot to go through there, but I know that a lot of the people who are listening will have heard me mention a number of times Matthew Walker's book, Why We Sleep.

    24. GP

      Yeah.

    25. CW

      Um, I think that's probably up there with my most ever listened to podcasts between him and Joe Rogan. And it's gonna be, it's gonna be really, really interesting to be able to dig into what I've...... heard, um, and, and read about so much and, and try and actually, um, elicit some of the answers that I think are maybe missing from my body of knowledge, and then give the listeners a little bit more, uh, a little bit more of an understanding of why sleep's important and, and, and what it does to people. And then I'm super excited to talk about Human OS as well. I, earlier on today, had a, a pretty comprehensive browse of the, uh, of the site, so we'll be able to finish up with that at the end, so a lot to get through today.

    26. GP

      Smashing. Sounds good.

  2. 6:38 – 9:29

    Do we actually know why we sleep? Evolutionary tradeoffs and core functions

    1. CW

      Fantastic. Um, so to get started, do you know why we sleep?

    2. GP

      No, not really.

    3. CW

      (laughs) That's great.

    4. GP

      So it's a longstanding question in sleep research, and there are many different ways that you can try and address it. What I would say is that there's no real consensus right now, and I think it's worth thinking about why we sleep from an evolutionary perspective. And when you think about sleep, and this is something that Matt discusses at length and with great clarity in his book, sleep's very strange in that while you're asleep, you can't eat, you can't gather food, you can't have sex, and you're vulnerable. And for all of those reasons, there should have been very strong evolutionary pressure against the development of sleep-like behavior.

    5. CW

      Incredibly vulnerable, right?

    6. GP

      Yeah, absolutely. But as far as we can tell, more or less all species studied have sleep-like behavior. We spend a third of our lives doing it. So the question is, why is that the case? And I think that in reality, it probably serves different functions in different species. What's interesting is that different organisms have very different sleep patterns, both the timing of their sleep and also how long they sleep, and there are various things that seem somewhat predictive of sleep. So things like the complexity of social networks, nervous system complexity, the type of diets the animals consume, but no one thing is strongly, is a strong determinant of sleep in animals. So anyway, what happens during sleep? Well, it's a period of adaptive inactivity, and one of the functions is probably to optimize the timing and duration of bouts of activity to do things like reduce the risk of predation and also to ensure food acquisition. Another function is energy conservation. But actually, if you look at the amounts of energy that you save by sleeping versus just being awake and relatively inactive, it's very, very small. So that's not a particularly persuasive-

    7. CW

      So evolution hasn't given us this because it lowers our requirement for food?

    8. GP

      ... doesn't seem to be the case.

    9. CW

      Mm-hmm.

    10. GP

      Not, not in humans. If, for example, you look at all of the studies that have been done on the effects of sleep restriction on energy expenditure, the effects are negligible. We're speaking about the amount of energy that's contained in a slice of bread.

    11. CW

      (laughs)

    12. GP

      It really is-

    13. CW

      Just have another, have another bit of bread, you'll be fine, honestly.

    14. GP

      (laughs)

    15. CW

      Stay up all night, off your face, on bread, and then the next day, you'll be fine.

    16. GP

      Well, bread has gluten in it and that will probably get you-

    17. CW

      Oh, no. You're gonna-

    18. GP

      I won't-

    19. CW

      ... trigger everybody. (laughs)

  3. 9:29 – 12:04

    Sleep stages explained: non-REM restoration, brain ‘waste disposal,’ and REM creativity

    1. GP

      (laughs) So anyway, there are also different things that we pass through during sleep, and each of those serves related but distinct functions. So if, for example, you look at non-REM sleep, non-REM meaning non-rapid eye movement, there are three stages of this type of sleep, each of which becomes progressively deeper, by which I just mean that it's harder to wake someone.

    2. CW

      Mm-hmm.

    3. GP

      Non-REM sleep, there are processes like nervous system restoration, energy conservation, and pruning away connections in your brain that you use during the day, but weren't highly used and therefore don't seem to be necessary to hold onto. During this stage of sleep, there's also a kind of waste disposal system that becomes active in the brain, and there was a study that was published about five years ago showing that during sleep in mice, the plumbing in the system effectively opens up and cerebrospinal fluid washes toxic debris out of the spaces in the system that's accumulated during the daytime, so that seems to be one of the functions of that particular type of sleep.

    4. CW

      Does that, does that explain an increase in clarity of thought the next morning after you've had a good night's sleep to one degree?

    5. GP

      Yeah, it would do. It would do. Absolutely. And then another stage of sleep that you enter after that deeper stage of sleep is the stage with which most people are most familiar, rapid eye movement sleep, which is that stage in which you dream. It's called rapid eye movement because of the ways that your eyes dart from side to side during this stage. It's quite strange in that even though parts of your brain are as much as 30% more metabolically active at this time than they are during wakefulness, your muscles are completely paralyzed so that you don't act out your dreams.

    6. CW

      (laughs) Yeah.

    7. GP

      What this creates is an environment in which you can take information that you've accumulated during the day and then consolidate it during deep sleep, and you can collide all these different sources of information in your brain to form new connections. And through those new associations, you seem to be able to generate creative ideas. And what's very interesting actually is that if you look at humans specifically, then we spend maybe 20 to 25% of our sleep in REM sleep, which is more than any other primate, but we sleep less than any other primate. And some people speculate that this disproportionately large amount of REM sleep that we have as humans has been fundamental to the development of our intelligence and our complex social structures. So that's quite interesting.

  4. 12:04 – 16:49

    Sleep and learning: spacing, breaks, and why sleep between study bouts matters

    1. CW

      That is interesting. I'd, uh, I'd seen the study that you're talking about to do with, uh, one study that related to new connections in the brain when you're asleep, and, um, recently did a podcast with the author of Make It Stick, Peter C. Brown, and during that, he said that one of the key determinants of your capacity to learn is...... doing focused, concentrated work and then going away from it and then coming back, and I think that that's generating new connections and viewing, um ... Anecdotally, you'd say you're viewing something with a new perspective, but it seems that that's actually being reflected physiologically within the brain.

    2. GP

      Yeah, and there are probably a couple of things to touch on there. So one is learning during the day and the importance of spacing, because it's been years and years, more than a decade since I looked at any of this research. But in psychology, there are so-called primacy and recency effects, which just means that you tend to remember what you learn at the start of a learning bout and the end of it too, and you don't remember the stuff in the middle so much. So what that means is that, let's say that you've got six hours in which to learn. You're better off taking regular small breaks, and then by doing so, you create more opportunities for these primacy and recency effects. And then while you're not doing learning, you want to take your mind entirely off the task. So that's one component to the puzzle.

    3. CW

      Mm-hmm.

    4. GP

      But another component to the puzzle is sleep bouts during learning or between learning periods themselves.

    5. CW

      Okay.

    6. GP

      And I don't know if this is something that you want to return to later, but the, the way that that happens is relatively well understood. There are specific aspects of the process that are controversial and there's not complete consensus on, but it's something that's probably worth understanding because actually it is information that you can use to improve your ability to, to learn.

    7. CW

      That's fascinating. Is the ... is the sleep, um, industry of researchers, is it quite dogmatic? Are there some pretty sort of, uh, standoffish camps? I don't know how militant the, uh, the sleep world is.

    8. GP

      Well, you're speaking about a bunch of academics, and I would put them quite firmly in the passive category as individuals.

    9. CW

      Okay.

    10. GP

      Never seen a fight at a conference.

    11. CW

      (laughs)

    12. GP

      But with, with that said, the- there is contention over some things.

    13. CW

      Mm-hmm.

    14. GP

      And I think that it's often the case that somebody's view will be ingrained early on, and then it will go a period of time without being challenged.

    15. CW

      Yeah.

    16. GP

      And there's been this so-called replication crisis in science recently, and it's received an awful lot of attention in the media. I think psychological research in particular has come under fire for the inability to reproduce the results of previously done studies. And what's nice now is that more and more journals are necessitating that people make their data open access after publishing so people can revisit what other scientists did-

    17. CW

      Mm-hmm.

    18. GP

      ... to make ... that they did in fact do what they said they did and to make sure that they haven't dredged through their data and tried to come up with a way of analyzing their data to support their hypothesis rather than going in there beforehand and saying, "Okay, this is how I'm gonna look at my research question, and regardless of what the results are, I'm sticking to my guns."

    19. CW

      Well, that's the, that's the scientific principle, right? You shouldn't be trying to make the research fit a, a previously held hypothesis. That's not the way that it's supposed to be, but I can imagine that a lot of people, once they've got their teeth ... once they're certain about something conceptually, they want the research to then reflect that.

    20. GP

      Yeah, and an issue is that it's difficult to publish negative findings in scientific journals. By negative findings, I don't mean that they're disheartening or anything like that.

    21. CW

      Mm-hmm.

    22. GP

      I mean there's no effect of A on B.

    23. CW

      Yeah.

    24. GP

      And, if-

    25. CW

      It's less, it's less glitzy, right? It's not as much of a ... Melatonin doesn't, doesn't affect, um, sleep quality isn't as much of an exciting title. Oh, that might actually be, but (laughs) something else that A doesn't affect B, it's not as attention grabbing, right?

    26. GP

      Yeah, it's not gonna get on the front page of The Washington Post anytime soon.

  5. 16:49 – 20:24

    How much sleep is optimal? Guidelines, variability, and the myth of ‘3-hour sleepers’

    1. CW

      I got you. So we understa- or we have a beginning of an understanding of what we think sleep is required for from an evolutionary perspective. Do we know how much is optimal? Is there a, an agreed upon time? It's kind of this wives' tale anecdote that eight hours is how much we need a night. Is that, is that correct?

    2. GP

      There are guidelines, but you can't take the guidelines and assume that you're correct, th- th- that they are correct for you as an individual. The guidelines vary according to how old somebody is. So if you look at young people, they need more sleep than adults, and for adults, according to the National Sleep Foundation, on average, we need seven to nine hours per night. But there is relatively substantial variability between people in sleep need. And one other thing that I'll add is that the amount of sleep that you need is a moving target. So I don't know what your experience is, but for me, for example, I generally find that I sleep more in the winter than I do in the summer, and I think that's probably somewhat related to the photoperiod.

    3. CW

      Mm-hmm.

    4. GP

      Also, if I'm going through a period in which I'm exercising particularly intensively, then I'll need more sleep. If I have a cold, then I'll need more sleep. If I'm stressed about something and I have a deadline on the horizon, then it's just as if the alarm clock in my brain just comes online a little bit earlier.

    5. CW

      Yeah.

    6. GP

      And for that reason, invariably I, I sleep less. So even though we have these generic targets, I think that actually fundamentally-... you give yourself the opportunity to get the sleep that you need by getting in bed on time. You focus on preparing for sleep as well as possible by getting in the right frame of mind, and also supplying with- your body with what it needs, ensuring that your environment around you is conducive to good sleep. And then you don't wake up to an alarm and you see how long you sleep. And it- it sounds facile to-

    7. CW

      (laughs)

    8. GP

      ... explain that way, but I- I do think that that is how it is. With all of that said, seven to nine hours is a good baseline for most people, and we understand more and more about some of the things that do influence why some people need more or less sleep. But some people, I think historically, have thought that there are those lucky few out there, the Margaret Thatches of the world, who need three hours of sleep and they function just fine, and that just doesn't seem to be the case.

    9. CW

      Mm-hmm.

    10. GP

      So of all of the genetic variants that have been identified so far, the particular variant that's associated with the shorter sleep phenotype is on average a variant that has adults sleep about 6.2 hours per night, which I think is probably far more than most people would expect the shorter sleepers to sleep.

    11. CW

      Is that the phenotype which is present in the same percentage of people that get hit by lightning? Is it the incredibly rare one?

    12. GP

      Yeah, that sounds about right, yeah.

    13. CW

      (laughs) Is it like, I think it's one in a hundred and twenty thousand or something like that.

    14. GP

      It's very rare, yes.

    15. CW

      (coughs) Right. So I think it's safe to assume that you don't have that (laughs) phenotype for the vast majority of people that are listening. So what that means is you need to be aiming for between seven and nine hours.

    16. GP

      Mm-hmm.

  6. 20:24 – 26:23

    Sleep loss and metabolism: prediabetes effects, overeating, and reward-driven food choices

    1. CW

      And just how important is sleep to our short-term and long-term health?

    2. GP

      That's a very big question. (laughs)

    3. CW

      (laughs)

    4. GP

      Okay. So, so where would you like me to start with that? We can speak about metabolism or...

    5. CW

      Let's take it from the top, wherever, wherever you think is best to set the scene and go from there.

    6. GP

      Okay. Well, I suppose there are different ways of looking at it. Obviously, you can't have an intervention in which over a very long period of time, you have one group of people shorten their sleep, and you have another group sleep as much as they like. So in order to get at the effects of sleep on the population level, people use epidemiology to study populations. And typically those types of studies will just have people answer questions about sleep and then researchers will associate how long people report sleeping with various health outcomes, and preferably they will also follow them up over time. So in those circumstances, prospective studies like that can be used to see whether short sleep at baseline predicts greater development of chronic disease further down the line, for instance.

    7. CW

      Okay.

    8. GP

      So that's- that's one way of looking at things. The problem with that is that there are all sorts of confounding variables, so it's ha-

    9. CW

      It's self, it's self-reported, right? It's hardly a, a scientific approach.

    10. GP

      Ye- well, it's, it is a scientific approach, but it's not objective.

    11. CW

      Okay.

    12. GP

      Like, th- that's the point. And in order to get a more objective handle on the effects of disrupted sleep on various outcomes, you need to look at sleep studies in which people come in the environment, into the laboratory environment, and they are given a certain amount of time in bed, and then you assess various outcomes of interest. So if we start with metabolism, for example, then we've known for about 20 years now that as little as five nights of shortening somebody's sleep to four hours per night results in otherwise healthy young people temporarily becoming pre- pre-diabetic.

    13. CW

      Wow.

    14. GP

      Not only that, they also tend to eat differently. So that effect is seen when somebody's diet is held constant, but if you let people choose what they eat, then on average, restricting somebody's sleep duration to a period of say, four to six hours per night tends to increase the amount of energy they consume by about 385 calories a day.

    15. CW

      Okay.

    16. GP

      Which doesn't sound like much, but of course health is the consequence of your behaviors over a long period of time. So the accu- th- the cumulative effect of all of these small impacts adds up to something meaningful, and 385 calories a day over the course of a year, that's the amount of energy that's stored in about 18 kilograms of fat tissue.

    17. CW

      (laughs)

    18. GP

      And I'm not saying, I'm not saying that you would gain 18 kilograms of fat tissue because you have this lipostat in your brain which will actively try to defend how much fat you carry.

    19. CW

      Mm-hmm.

    20. GP

      So it's relatively unwavering, but you are likely to gain weight, let's put it that way.

    21. CW

      So sleeping- sleeping less means eating more, and it's- I'm gonna presume that people, when they are tired, I know for myself, if I've had a really bad night's sleep or if I haven't slept enough, I'll reach for less healthy foods as well.

    22. GP

      That's exactly right. Yeah. So it's not only the amount of food that people are eating, but it's also the quality of food that seems to be affected by sleep loss. And in the last maybe decade, people have started to look at the effects of sleep loss on patterns of activity in the brain in response to food stimuli. So for example, you can have somebody come into the lab, you can completely deprive them of sleep over the previous evening and then show them images of cupcakes and cookies. And you can compare their brain activity in that situation to when they're allowed as much sleep as they would like.... and after the sleep deprivation, areas of the brain that are involved in motivation and reward to acquire food lights up like a Christmas tree.

    23. CW

      Wow.

    24. GP

      And not only that, but the prefrontal cortex, which is the most recently evolved area of the brain, you can think of it as the brain CEO or the part of the brain that lets you do the right thing when it's more difficult thing to do-

    25. CW

      Mm-hmm.

    26. GP

      ... is less well-connected to other regions of the brain, so it doesn't have the ability to override those urges. And some of the more primitive parts of the brain and the limbic system tend to be more active too. So you have this double whammy of brain activity that makes it increasingly hard to avoid succumbing to the temptations of things that our bodies are hardwired to gravitate towards, like lots and lots of calories.

    27. CW

      That's interesting. So I know a lot of my friends that do sports and some of them will be prepping for bodybuilding competitions, fitness shows, CrossFit competitions that are coming up. Um, specifically when they're in a deficit, if they're dieting hard, trying to cut before a show, I know that they struggle with their sleep.

    28. GP

      Mm-hmm.

    29. CW

      So what you, so what you're saying is that the poor night's sleep that they've potentially got, perhaps because of being hungry or perhaps just because of stress about the show or whatever it might be, is making the next day of deficit eating even more difficult and requiring even more willpower to not go and get a cookie from the, the cupboard?

    30. GP

      Yeah. Unfortunately, that is a vicious cycle.

  7. 26:23 – 31:39

    Sleep, mood, and circadian rhythms: what the clock does and why misalignment hurts

    1. GP

      So if you look at sleep duration and neurodegenerative disease and also various mood disorders, bipolar disorder, major depression, there seem to be strong associations there. So it, it appears to be the case that almost no mid- mood disorder, in almost no mood disorder people experience normal, healthy sleep. There's always some sort of disruption. And what I'm most familiar with is the effects of circadian system disruption on mood and also how circadian rhythms are misaligned in certain mood disorders, but-

    2. CW

      Can, can you briefly explain what a circadian rhythm is for us, please?

    3. GP

      Sure. So organisms evolved in this 24-hour light-dark cycle that we experience each day. Not only that, that's nested within the context of these seasonal changes in various environmental conditions. And to thrive in those environments, they needed to develop timing systems that helped them anticipate to daily changes in the environment, change in temperature, cha- change in light exposure, because with that came changes in food availability and predation risk and so on. And over the course of millions of years, almost all, not all organisms evolved these internal timing systems. And a circadian rhythm is a rhythm that has a period of about 24 hours, but it's not precisely 24 hours. These rhythms are self-sustained, so they repeat of their own accord day after day. They're persistent and they're untrainable. So because they're not exactly 24 hours, they need to be reset each day and the strongest untraining agent in the environment that resets our biological rhythms as humans is the light-dark cycle. And that does so by way of, it's called the photoneuroendocrine system, but it's just the way that light is perceived by specialized cells in the eyes and these specialized cells then relay information about light exposure to a so-called master clock in the suprachiasmatic nucleus in the hypothalamus. And this master clock just sits atop where the two optic nerves that come from the eyes to the visual cortices is placed, and it samples information about the light environment. Over time, it then knows what time of day it is outside roughly, and it uses various ways of sending this time of day signal elsewhere in the body. So perhaps the best known of those is via the pineal gland and subsequently melatonin synthesis. So as light comes into your eyes, this signal is then transferred back to the pineal gland via the master clock and light exposure offsets melatonin synthesis. During darkness, that signal is no longer coming in, so the pineal gland synthesizes melatonin and then melatonin relays this signal of darkness throughout the body because many of your body's tissues have their own melatonin receptors-

    4. CW

      Mm-hmm.

    5. GP

      ... and through that mechanism, they know that it's dark outside and they should be performing nighttime activities. But it's not only melatonin that the system uses. It also uses things like changes in body temperature each day. Another very important hormone in the circadian system is cortisol. And if you look at the daily rhythm of cortisol, then in anticipation of waking each day, you see this big spike in cortisol in healthy people, maybe an hour or so before waking up. And what that does is mobilizes stored energy reserves in things like your muscles, it increases your blood pressure, your heart rate, and it readies your body for the day ahead. So that's one other key agent. And then the master clock itself also sends out or secretes its own...... substances that then reach other areas of the brain and help coordinate the timing of all these different body systems. So, the circadian system as a whole optimizes your body for the needs of the present moment and in this way, for example, you will be at your strongest during the daytime. Your digestive system is best set to digest food during the active period and, at nighttime, your appetite will naturally wane. You'll have a drop in core temperature and brain temperature, and that improves your ability to fall asleep. You will see a spike in growth hormone, which will help you preserve your lean body mass overnight. And overall, the net effects of this symphony, if you like, is to make sure that if everything is working properly, then your whole body is optimized for the needs of the present moment.

  8. 31:39 – 39:43

    Daylight savings, seasons, and mental/physical risk spikes

    1. CW

      Okay, so that's what circadian rhythm is. I'm gonna guess that that, um, that requirement for light and dark to regulate our sleep is why seasons, specifically in places like the UK where we do have quite a big disparity between summer day lengths and winter day lengths, I'm gonna guess that that's one of the reasons that people may struggle to wake up in the morning or may find sleep different, uh, between seasons. Is that right?

    2. GP

      Yeah, it is. And there's not actually very strong evidence of seasonal differences in people's sleep patterns in art- in artificially lit environments because everywhere you go in the UK, you can't escape a streetlamp-

    3. CW

      Yeah.

    4. GP

      ... or light from buildings or whatever. But if you take people and you have them go camping during the winter and you have them go camping during the summer, then you will, you will see quite rapid changes in people's sleep patterns that track changes in the light-dark cycle. And one thing that you mentioned there, which is relevant to mood disorders, to circle back to that, is how that changes over time and how some people may find it hard to wake up at certain times of year or just feel worse. So seasonal effective disorder, for instance, is quite commonplace, and it's more commonplace the further from the equator that you move, so at higher latitudes. And what you find is that around the time that we transition and the clocks switch back each autumn, you tend to see a spike in people who report experiencing depression at those times. And actually, the circadian system is a point at which you can intervene in order to try to help those people. So-

    5. CW

      Do you think that that's, do you think that the reports of depression are to do with the single night of l- lack of sleep or that that is a marker that the days are getting to a, a length where that would occur?

    6. GP

      Yeah, I, I think it's probably a bit of both because-

    7. CW

      That's crazy that a single, a single change in time would elicit a, a response from, you know, a general population.

    8. GP

      Yeah, I, I, I think the strongest evidence of the change in time producing that kind of response is daylight savings time. So, during the springtime when we lose an hour of sleep each year, you tend to see a spike in traffic accidents at that time of year, for example. There's also some relatively weak evidence that you might see an increase in cardiovascular incidents at that time. So an increase in things like heart attacks.

    9. CW

      Off the back of one night?

    10. GP

      Well, it's, it's one night acutely, but of course, people have to keep waking up early.

    11. CW

      Mm-hmm.

    12. GP

      So let's say that the first night you lose an hour of sleep, and then you start to adjust to being a little bit earlier, but you never fully adjust. So maybe the second week you're losing 45 hours of sleep.

    13. CW

      Mm-hmm.

    14. GP

      And the third week, you're losing 30 minutes of sleep and, and so on.

    15. CW

      Yeah.

    16. GP

      I think that there's, there's a cumulative effect there over time. So I think that's, that's probably the best evidence of that type of acute disruption to sleep having long-term consequences for lots of people. But also, there, there is this change in photoperiod that seems to independently affect risk of people experiencing certain things. And-

    17. CW

      Okay.

    18. GP

      ... and I think particularly up at, up at the poles, people are at very high risk for that.

    19. CW

      Yeah, definitely. I mean, there's periods, entire months where the sun doesn't set.

    20. GP

      Yeah.

    21. CW

      If, if you were ever (laughs) , if you were ever gonna be somewhere and suffer with seasonal affective disorder, it's gonna be, it's gonna be either of the poles. So, um, going back to moods, um, have we... Uh, is there any research which shows a link between someone with sleep l- uh, uh, sleep deprivation and depression?

    22. GP

      That's an interesting question because actually, historically, sleep deprivation has been used as an antidepressant.

    23. CW

      Really?

    24. GP

      Yeah, a single night of sleep deprivation. So quite often it's the case that people with depression will experience poor sleep, and if you deprive somebody of sleep over one night, then they have this really strong increase in the pressure to sleep, and then in subsequent nights, they sometimes find it easier to get back onto some sort of consistent sleep schedule, so-

    25. CW

      Like wiping the Etch A Sketch board clean, so to speak.

    26. GP

      Kind of, yeah. But, but also during that night of sleep loss, people's mood does tend to improve acutely, and we don't really understand fully why that's so. I haven't looked closely at that research. I know that somebody who I've collaborated with at University of Surrey has published some work on that, and they looked at the metabolome, which is where you basically take a biological sample, so let's say you take somebody's blood...... and you look at all of the metabolites that are in that blood sample at that particular time of day, and you can take them at various points during the day and look at how the metabolites respond to various interventions, so for example, diet or sleep loss. And if you look at the effects of sleep loss, and I think that there's evidence that you see changes in serotonin signaling, serotonin metabolites, and serotonin's a neuromodulator, neurotransmitter, which is important to things like mood and sexual function, motivation, all sorts of things. But I think that the strongest evidence, of course, that serotonin is critical to that is the fact that what's the most common antidepressant medication people use? It's-

    27. CW

      SSRIs, yeah.

    28. GP

      ... reuptake inhibitors, which basically prolong the a- the amount of time that serotonin is in the synapse between neurons in the brain, a bit- reduce the clearance of the serotonin from those. So sleep deprivation does have these short-term antidepressant effects, but those effects aren't sustained over time, and actually, uh, as I alluded to before, what you tend to see is that over the long term, of course, worse sleep is associated with poor mood. Uh, the tricky thing, as I, as I briefly touched on, is just that often somebody sleeps poorly, but how do you causally tie that to some specific outcome in an observational study when people who sleep poorly might be smoking more, they might experience more stress at home, perhaps they drink, they have all of these other lifestyle behaviors that negatively affect the e- the health outcome in question?

    29. CW

      Yeah, it's very difficult to isolate, right?

    30. GP

      Yeah, that's it.

  9. 39:43 – 50:54

    Shift work risks and the two-process model: circadian wake drive vs sleep pressure

    1. CW

      Very much so. Um, so we've touched on sort of short and medium-term, uh, effects of, of sleep. What about when we're talking over a lifetime for someone who potentially does shift work or has got chronic, uh, is chronically underslept? What are the sort of things that can happen there, and then conversely, what are the effects of someone who's sleeping well over that period?

    2. GP

      Yeah, so o- over a lifetime, the best data we have really are those types of observational data. And if you look, for example, at obesity, then people who report sleeping less than, I think, seven hours per night, uh, at 45% higher odds of developing obesity later in their life. That's based on results from meta-analysis, which is a study of studies which was published last year.

    3. CW

      That's over, that's seven hours, which I think for a lot of people would, they'd consider, "Oh, well, you know, I'm only one hour off eight, and eight is what I'm supposed to get."

    4. GP

      Yeah. Yeah, exactly.

    5. CW

      So-

    6. GP

      And of course, that could be misreporting, but when you're speaking about, in this instance, 11 s- 11 studies on nearly 200,000 people, then that's actually quite persuasive as a result.

    7. CW

      There's got to be some proof in the pudding, yeah.

    8. GP

      Yeah, you would think so. But then there are also lots of other conditions that you could, you could look at, so neurodegen- you know, neurodegenerative diseases like Alzheimer's or dementia, and again, you see that same type of association.

    9. CW

      Is there an increased risk?

    10. GP

      There is an increased risk with people who report poorer sleep. Yeah, absolutely. And there are different ways in which we can think about poor sleep, too. So in this conversation so far, we've mostly focused on sleep duration, but also there's of course, sleep efficiency. So let's say that you go to bed each night at 10:00 PM and you wake up at 6:00 AM, you're in bed for eight hours, you're not going, going to be asleep the entire time.

    11. CW

      Mm-hmm.

    12. GP

      Sleep efficiency is the proportion of that sleep period in which you are actually asleep. So there's efficiency there. There's also sleep architecture, the way that you cycle through the different stage of sleep. There are specific sleep disorders, of course, of which there are over 100.

    13. CW

      Oh, wow.

    14. GP

      There's a sleep timing and something that's gained more attention recently is sleep timing variability. So consistency, consistency in when people go to bed and wake up does seem to be important. It's probably-

    15. CW

      Re- regardless, regardless of duration and quality, just an upset in the regular cycle of the sleep times of sleeping and waking?

    16. GP

      Yeah, I think regardless of duration. I'm not sure that I would say regardless of quality, because actually when you go to sleep influences the quality of that sleep.

    17. CW

      Uh-huh.

    18. GP

      That's related to the way that sleep is regulated. And I can, I can just speak briefly about that, if you'd like.

    19. CW

      I'd love you to speak deeply about it, as I know that a lot of the guys who I work with... To give you a tiny little bit of background, my job as a club promoter means that...... if I, I've tracked my sleep for around about 1,300 nights using the Sleep Cycle app on my phone. And if you were to look at the data, the variability that you have in my sleep and, uh, sleeping and waking time is almost 24, it's almost global, it's almost 24 hours that very regularly throughout the week I'll go to bed when I don't have work at around about 11 o'clock or 12 o'clock and get up at sort of between, anywhere between 6:00 and 8:00. But then when I go to work, I'll be working until 3:00 in the morning, I'll get home, go to bed at 4:00, wake up at 10:00 or wake up at 12:00 and, you know, this is, I'm only one person out of a massive, a massive nightlife industry. Then add in shift workers and, you know, all manner of other people, there's a huge, a huge proportion of the population that this will affect, I'm gonna guess.

    20. GP

      Yeah, absolutely. And if you look at shift work, for instance, and that is a form of shift work, of course-

    21. CW

      Yeah, yeah.

    22. GP

      ... um, roughly 20% of people in Europe and North America do shift work. And it doesn't just affect those people, it affects their loved ones too. So you have all these secondhand shift workers who have to tolerate you poor shift workers who, who do that work, and it's really important work because-

    23. CW

      You wake, you wake the missus up when you get in at 4:00 AM and then-

    24. GP

      That's right.

    25. CW

      Yeah.

    26. GP

      Yeah. So-

    27. CW

      What are the effects on, on shift work, and what are the effects of variable sleeping and waking times on long, short and long-term health?

    28. GP

      Yeah. So shift work, if, if you look at all the studies that have been done and then compile those results, then it's associated with all sorts of negative outcomes, as, as you might imagine. And-

    29. CW

      Well, f- give it, lay it, lay it to me frankly, Doctor. Tell me what it is. (laughs)

    30. GP

      If, if you look at the strength of those associations, and i- it varies depending on the outcome, but shift work, nightshift work specifically is associated with things like obesity, diabetes, heart disease risk, stroke. Breast cancer's received some attention. Certainly some cancers have stronger evidence than others. I think that whether it's associated with breast cancer has come into question recently, because there was a large report that was published that suggested that might not be the case. But almost everything does seem to be affected. The question is that, the question is what i- what is it about shift work that predisposes people to that? Because it's a complex exposure scenario in which it's not just sleep that's disrupted or circadian rhythms that are disrupted. You also have people doing all of these things and of- often working stressful jobs, for example, that will also affect their risk of various diseases. So that's all, that's all-important to understand. One thing just to circle back to why when you sleep affects the quality of your sleep is that if we look at how sleep is regulated, then there are two processes. And one of those processes influences how awake you feel at any given time. That's regulated by your circadian system. And what happens is that each day you wake up in the morning and then over the course of the day you see this increase in the drive to stay awake, and then around the time that you normally fall asleep, there's a sudden drop in this wakefulness drive. The other process is the sleep process, and that's the process that builds with prolonged wakefulness. So the longer that you've been awake, the more sleepy that you are. And that's not a perfectly linear effect, but that's true to some degree. And there are various physiological correlates of that, and these are called somnogens. You can think of them as chemical barometers of how long you've been awake. So as I'm having this conversation with you, these are accumulating in our brains right now and they're increasing our pressure to fall asleep.

  10. 50:54 – 56:54

    Coping strategies for irregular schedules: banking sleep, forbidden zone, light and caffeine timing

    1. CW

      Yeah, I could, uh, I can definitely attest to that as well. So, to give you some, um, th- this is, this is probably like patient zero for bad sleep for you, but I'll, uh, I'll give you the, the example anyway. Very typically for me, if I've got a long day in the office followed by a trip to Manchester from Newcastle to run one of our events, I'll wake up at maybe, I'll try and push my waking time a little bit further back, so I'll wake up at 9:00. I'll work, and then I have to drive back from Manchester to Newcastle. I'll go to bed at 6:00 AM, and then looking at my clock, I'll think to myself, "24 hours from now, I'm gonna want to be getting up because it'll be a Monday and I'll want to start my week on a good note." But that means that at 6:00 AM on Sunday morning, I need to fall asleep, wake up, fall asleep, and wake up in the space of 24 hours. And, you know, as much as, like, getting up and getting after it can be viewed as an admirable quality in a 21st-century, um, corporate society where, you know, everyone's trying to be successful, it doesn't sound like that's the best thing for, for my health.

    2. GP

      No, it probably isn't.

    3. CW

      (laughs)

    4. GP

      But it's unavoidable in that particular scenario. So, the question is, what do you do to cope with that sleep loss? And I think that what you try to focus on is getting some sleep and coping with the sleep loss during the way, but doing so in such a way that you don't interfere with your ability to fall asleep the following evening. And another thing to consider is that you can try and preemptively prepare for those episodes by banking sleep beforehand. So, banking is an apt analogy here, in that, let's say that you're trying to accumulate a certain amount of wealth in the coming week and each minute of sleep that you get represents one, one pound, okay?

    5. CW

      Mm-hmm.

    6. GP

      This week, you try to, to bank as many pounds as possible by getting as many minutes of sleep as possible, knowing that next week you're not gonna get that much sleep, and subsequently, next week you're gonna be in debt. So, that- that's how you try to prepare for it. So, with you, Chris, let's say that you've got a really good week this week, and you can, you can try to be consistent in your patterns knowing that next week you've got several events.

    7. CW

      Mm-hmm.

    8. GP

      That will help protect you in certain ways against the negative effects of the sleep loss that you will experience the next week. It's h-

    9. CW

      That's crazy. So it, it is, it is literally like a savings account.

    10. GP

      Well, it is if you have a history of incomplete sleep. So, let's just say that there's a fairy tale scenario in which somebody's always slept perfectly.

    11. CW

      Yeah.

    12. GP

      That person couldn't necessarily bank sleep, because they don't have any sleep debt from their previous life.

    13. CW

      Yeah.

    14. GP

      However, that person doesn't exist, as far, as far as I can tell, at least.

    15. CW

      Mm-hmm.

    16. GP

      And for that reason, we probably all have something of a sleep debt to pay off. And banking, although it might not be the case that it's technically possible, it is effective, nonetheless, in terms of what we're trying to achieve.

    17. CW

      So, you could w- would you aim to push maybe an extra half an hour or an extra hour for the couple of days preceding, uh, a late night?

    18. GP

      Yeah. I, I'd go about it in a few different ways, and I think the one thing that's important to recognize is that trying to force yourself to just go to bed earlier might be a fool's errand. The reason is that the wake drive that I mentioned before is at its highest just before you try to fall asleep. And some sleep researchers refer to that as the forbidden zone for sleep.

    19. CW

      (laughs)

    20. GP

      You just have a really hard time falling asleep at that particular time.

    21. CW

      That's lying awake, staring at the ceiling, right?

    22. GP

      That's exactly right, yeah. So, so what you would do then is potentially try to shift your body's internal clock, your circadian system, a bit earlier, and you'd do that by exposing yourself to lots and lots of bright light early in the day, perhaps doing some exercise early in the day too, and then trying to reduce your nighttime light exposure and starting your sleep routine a little bit earlier.... okay? So that's, that's one way of intervening. Another thing is to address your caffeine intake. So while you're trying to bank sleep, try to taper that or maybe go cold turkey and use caffeine-

    23. CW

      Oh, don't do it to me, Greg, please. (laughs)

    24. GP

      But it does make sense because-

    25. CW

      I know, but you're killing me. (laughs)

    26. GP

      Caffeine is an adenosine receptor antagonist, so one of the somnogens which we spoke about earlier is adenosine, which is a breakdown product of ATP. So as your brain expends energy during the day, it releases ATP from presynaptic neurons into the extracellular fluid that bathes brain cells.

    27. CW

      Okay.

    28. GP

      And this ATP can act directly on sleep circuits in the brain to promote sleep. It can disinhibit... sorry, it can hi- inhibit wake-promoting circuits too, or the ATP can be broken down to adenosine and that can also have similar effects. And anyway, caffeine blocks the interaction of that adenosine with its receptors.

    29. CW

      It binds to the same receptor, right?

    30. GP

      So basically, you, you've got all of this... it, it... that's exactly what it does. So you've got all this sleep in a signal, but it's like somebody shouting and there are no ears there to hear the person shouting.

  11. 56:54 – 1:04:36

    A practical sleep prescription: day behavior, bedtime routines, and light management without overkill

    1. CW

      Okay. Well, that's a... that's a, that's a really cool... a really cool little bit of advice there. So I want to... we've, we've touched on the effects of sleep and, and how important it is, but I wanna talk about enhancing your circadian system function, uh, and sleep, and then also how we can cope with, with sleep loss. And then we're gonna finish on, uh... finish on some stuff to do with human OS. So if you were to write a prescription for someone who wanted to have as good sleep as they could, have you got some principles that they should be sticking to?

    2. GP

      Yeah, many principles, and I think that it's worth starting with the daytime. So during the day you want to be physically active, and the reason that comes back to adenosine and the fact that as you burn more energy, you accumulate more adenosine and, and then that helps you sleep more deeply at... that night. During the day, you also want to expose yourself to lots of bright light. And because the amount of energy that your brain burns, you wanna do cognitively demanding work. And also, that can include other activities, so things like meditation are actually quite taxing and do consistently improve sleep, not just because of that effect, but also because they probably have roles on things like stress regulation too.

    3. CW

      The parasympathetic nervous system and stuff like that, right?

    4. GP

      That's right. Yeah. And then during the nighttime, I think that it's valuable for somebody who's not in a very consistent pattern to set an alarm in anticipation of their bedtime. So let's say that your sleep routine takes you an hour, then you would set your alarm for an hour before bedtime.

    5. CW

      Yeah.

    6. GP

      Regarding your bedroom itself, you want to make it stress-free, so keep it uncluttered and use it for sleep and sex only.

    7. CW

      (laughs)

    8. GP

      And then light exposure is really, really important. So during the day, get outside, lots and lots of bright light, and then probably around two hours before you intend to go to bed, you want to start reducing your light exposure. And where possible, I would avoid artificial lighting, but I know that that's often not possible. So what can you do in those circumstances? You can use apps on your devices, so things like Twilight for Android systems or Night Shift mode for iPhones. You can use f.lux on your laptop, which is on mine right now.

    9. CW

      Mm-hmm.

    10. GP

      You can also use things like blue-blocking glasses. I don't personally use them, I just don't have the self-confidence to wear them.

    11. CW

      We're getting into Ben Greenfield territory with blue-blocking glasses, aren't we?

    12. GP

      Yeah, a little bit. Little bit.

    13. CW

      (laughs)

    14. GP

      So there's that too, and then as you fall asleep, either use blackout blinds in your bedroom, good curtains, or just use a sleep mask.

    15. CW

      Mm-hmm.

    16. GP

      You-

    17. CW

      Is there a... is, is there any substance to photoreceptors in your skin being able to detect light?

    18. GP

      In short, I, I don't think so. There was a paper that was published in the journal of Science in 1997 which received a lot of airtime. This was the kind of journal article that would get on the front page of The Washington Post because it was novel, but it wasn't replicated. And what they did is they shone light on the back of somebody's knee, I think-

    19. CW

      (laughs)

    20. GP

      ... during the day, and, and supposedly it was able to shift the timing of the circadian system.

    21. CW

      Okay.

    22. GP

      And it... it hasn't been shown since. So as far as I'm aware, that's not the case. I know that there are these devices now that do things like shine bright lights in your ears and-

    23. CW

      Yeah, there's all, all kind of weird and wonderful, uh, sleep aids now, isn't there?

    24. GP

      Yeah, and, and not just for sleep, because light actually has a variety of other effects, they're non-image-forming effects, but effects that are... either relates to the circadian system or they have effects on things like cognition. So bright light exposure during the daytime routinely will acutely boost someone's mental performance if they haven't been exposed to bright light before that. And that's why actually one of the ways to cope with sleep loss that we'll come to is making sure that you spend some time outside. So that is part of the picture, but these devices anyway...... that shine-

    25. CW

      The shining lights in your ears.

    26. GP

      Yeah, I'm, I'm, I'm not sure about them. I haven't looked close at the research.

    27. CW

      You don't have a pair?

    28. GP

      I don't have a pair.

    29. CW

      (laughs)

    30. GP

      No. And I, I'm not aware of any sleep researchers that seem particularly persuaded by their utility. I'll put it that way.

  12. 1:04:36 – 1:10:55

    Temperature and sleep setup: hot shower paradox, cool rooms, socks, and white noise

    1. CW

      application elsewhere. Um, what about sleep posture and sleep temperature and the sleep environment that you're actually laid on? Did you, have you looked into this much?

    2. GP

      Yeah, I've looked at temperature. Posture's interesting and I... It's funny actually. I'm, I'm interviewing a guy for our podcast, Stuart McGill, who's arguably the world's foremost expert in spine biomechanics, in a few days time, and I'm curious to hear his thoughts on that. I think that the best sleeping posture is likely highly dependent on the person. So-

    3. CW

      Probably the most, probably the most comfortable one, right?

    4. GP

      Surprise, surprise.

    5. CW

      (laughs)

    6. GP

      Yeah. So, b- but anyway, some people's spines are very flexion intolerant. If they bend over to tie their shoes or whatever, if they sit at a desk all day, then their spines really don't like being in that position. So sleeping on their-

    7. CW

      (coughs)

    8. GP

      ... back over time might not be wise. Other people are really extension intolerant. So if they arch back and look up at the ceiling, then they experience pain. That's a pattern you see in people like gymnasts and for those people, sleeping on their front is gonna be unwise. I think for most people, sleeping on the side is probably smart, and I generally find that people often benefit from having a, a pillow between their knees during sleep too, something between their knees just to keep them slightly ajar. And I, I suspect that's related to the spine, but I don't actually know what the mechanism is. It's just that many people seem to be more comfortable in that position.

    9. CW

      But you and Mr. McGill will hopefully find that out. By the time that we've published this, I think yours will be up as well so I'll make sure that I link that in the show notes for the listeners who want to go and do some further reading or further, further listening it should be. So how about temperature?

    10. GP

      Yeah, so temperature is interesting in that what we wanna do is raise the temperature of the skin by a couple of degrees shortly before sleep, and this is counterintuitive because during sleep the temperature of your brain drops as you progress into deeper sla- stages of sleep. So during deep sleep it's at its lowest, and then during REM sleep as the metabolic activity in your brain rises, it goes up again.

    11. CW

      Is that just as a, is that as a byproduct of the activity or is that...

    12. GP

      Yeah, it is, it is partly a byproduct of the activity, but things that you can do to facilitate that drop-

    13. CW

      Yeah.

    14. GP

      ... also help you fall asleep. And by raising the temperature of your skin, you create this gradient between your core temperature, deep within you, and the temperature of your brain and the temperature of your skin, and that helps you radiate heat out from your core, improving your ability to drop the temperature of your core and your brain. So a simple way to achieve that is a hot shower, typically about 10 minutes at about 40 degrees C is about right, within maybe an hour of when you go to bed and then-... the, the parts of your body are also relevant too, because your hands and your feet, and probably your ears too, are relatively unique in their structure. They have a very big surface area, but not such a big volume, and that makes them very effective at transferring heat to the environment.

    15. CW

      They're the body's, the body's radiators, right?

    16. GP

      Yeah, exactly.

    17. CW

      (laughs)

    18. GP

      So when you get out of the shower, you want to keep your feet warm, so you stick some socks on and that seems to consistently help people both fall asleep faster, stay asleep, and perhaps sleep a little bit longer too. There's been some research published on that in the last few months.

    19. CW

      By keeping, by keeping their socks on?

    20. GP

      Yeah. Well, in that instance it was actually using these special socks-

    21. CW

      (laughs)

    22. GP

      ... that warm the feet slightly during sleep.

    23. CW

      Okay. So e- all of the, um, all of the girlfriends that are listening who absolutely hate their boyfriends going to sleep in socks, they're actually, they actually need to side- sideline their concerns about fashion and focus more on the fact that they're, they're potentially getting a little bit better sleep.

    24. GP

      They need to stick their sleep masks on, and then they-

    25. CW

      Yes, and they do, and they can't see the socks. Yes. We've found the solution. So you've had the hot shower before you go to bed, and that is going to help you radiate heat away, right, from your core?

    26. GP

      Yeah, but then, of course, you don't want the surrounding temperature to be too high, and you want your bedding to let you continue to lose heat. So it needs to be able to effectively transfer heat. And I know there are some companies out there that say that their sheets are better than other sheets at, at doing this. I would just look into them. There are ... (laughs) there are a couple of companies I'm familiar with. One of them is called Sheex and-

    27. CW

      It's a good name, it's a good name for a sheets company.

    28. GP

      Absolutely.

    29. CW

      (laughs)

    30. GP

      And you can look into those. But anyway, the, the point is that you don't want your bedroom to be too warm. You also don't want it to be very cold, because again thinking about evolution, if the environment, if the environmental temperature was very hot or very cold, then that's a stressor to the body, and it's a signal that you don't want to hang around because otherwise you're gonna disrupt your ability to regulate your internal environment. And for that reason, the bedroom needs to be comfortable but cool.

  13. 1:10:55 – 1:17:29

    Substances and sleep: caffeine cutoffs, alcohol’s REM rebound, and CBT-I before sleep drugs

    1. CW

      Um, so what else can we do to enhance our sleep or our circadian system function?

    2. GP

      Okay, so just sticking with sleep, a couple more things. One is related to diet. So we spoke about caffeine briefly earlier. I would just say caffeine typically is metabolized relatively slowly, and for that reason you don't want to consume it too late in your day. As an arbitrary cutoff, I would say try to not consume caffeine any later than about nine hours before you plan to fall asleep.

    3. CW

      Oh, wow.

    4. GP

      You know?

    5. CW

      That is, that is potentially very early for a lot of people, isn't it?

    6. GP

      Well, it's, it's, it's gonna be hard for, for shift workers in particular.

    7. CW

      Yeah.

    8. GP

      But I, but I think also that caffeine is something that when you go through the initial period of cutting your caffeine intake, it sucks. Many people have-

    9. CW

      (laughs)

    10. GP

      ... very bad headaches. But it passes.

    11. CW

      Yeah.

    12. GP

      And over time, as your sleep quality improves, the nice thing also is that you become more sensitive to caffeine again.

    13. CW

      Yeah, so you need less. So you net a benefit on a number of different fronts.

    14. GP

      Yeah, exactly. And then y- when you do use it for those night shifts infrequently, it has a very strong alerting effect on you.

    15. CW

      Mm-hmm.

    16. GP

      So you improve your sleep, you feel terrible for a couple of days. When you're over the hump, it's all good. So anyway, I would say no more than about two milligrams of caffeine per kilogram of body mass, so if you're 80 kilos, then that's a bit more than a, a coffee. I know that's an awful lot, but-

    17. CW

      (laughs)

    18. GP

      ... keep that, keep that by nine hours before bed.

    19. CW

      The half- the half-life is, is, it tails off very slowly, doesn't it?

    20. GP

      Half-life is about six hours, yeah.

    21. CW

      Yeah.

    22. GP

      And the half-life, for listeners, is, is just the amount of time that it takes for the caffeine concentration in your bloodstream to reach half of the peak value of the experience after consuming the caffeine. So another thing is alcohol. And a lot of people use alcohol as a sedative, and alcohol does reduce the amount of time that it takes people to fall asleep and increase the amounts of deep sleep that people get early in the night. But then later in the evening, as your liver clears the alcohol, your body tries to frenetically try and catch up on the lost rapid eye movement sleep. And what tends to happen is you have these bizarre dreams and your sleep also fragments, so the quality of your sleep is reduced.

    23. CW

      I think this is, um, something from, that I'd read with Matthew Walker's book, which is the important distinction between sleep and sedation when using substances to assist you. I think the same came up with regards to marijuana.

    24. GP

      Yeah, that's right and many sleep drugs are hypnotics, so they, they, they put you in a more suggestive state, and, and you can, you can fall asleep more easily from that. But they don't necessarily produce physiological sleep.

    25. CW

      It's time under the-

    26. GP

      It's-

    27. CW

      ... time under the curve that you're after, right? Not just the planting the flag in the ground of I am no longer awake.

    28. GP

      Yeah, yeah, and it, it, it's a, it's a real issue and actually for people who struggle with sleep, one thing that I always say is that if, if you have insomnia, the first port of call is always CBT-I, cognitive behavioral therapy for insomnia. If you're in the UK and you have insomnia, then I think that the NHS will subsidize an online CBT program and what it is, is a sleep education module to teach you about sleep hygiene. It's very effective. Very, very effective and it's as effective online as it is in-person too, so go that route before you touch any of the sleep drugs. I think sleep drugs occasionally have their place, so let's say that, Chris, you fly out to Hawaii.

    29. CW

      Yep.

    30. GP

      And you're there for two days, and by the time you go to bed that evening, it's the time at which you would normally wake up back at home and there's no way that you're gonna fall asleep.

  14. 1:17:29 – 1:28:15

    Melatonin: when it helps (jet lag/shift work/aging) and when it’s mostly wasted money

    1. CW

      Um, so what about, and I'm gonna touch on it because I was recently in America-

    2. GP

      Mm.

    3. CW

      ... and this is, this, this seems so widespread I knew that I was gonna have a sit down with you, so I wanted to ask some people. Um, of a group of, uh, five men and 10 women that I was sat around a table with which is definitely not a representative sample but, um, 10 out of the 15 of them all use melatonin every night and all of them reported using the tablets at least, uh, a couple of times per year.

    4. GP

      Okay.

    5. CW

      The tablets that they were referring to mostly were sublingual ones which, uh, dissolve under the tongue. I know that melatonin isn't available in the UK so this may be a supplement that a lot of people who are listening have never tried-

    6. GP

      Mm.

    7. CW

      Um, have you had a look at much research to do with melatonin? Uh, I, the, I guess it's external melatonin or...

    8. GP

      Yeah, I have, well, the, the final chapter of my PhD was, was on this topic.

    9. CW

      Oh, well you, you, you should, you should, uh, know a little bit about it then.

    10. GP

      Yeah, I, I wouldn't claim that but, but anyway, that's, that's interesting and what you're saying is that those people take it when they're at home on local time, but they think that it helps their sleep.

    11. CW

      Exactly that and-

    12. GP

      Yeah.

    13. CW

      ... multiple, multiples of this group were combining that with wine and of that, a smaller subsection were combining it with wine and weed.

    14. GP

      Yeah, so, so polypharmacy isn't smart-

    15. CW

      (laughs)

    16. GP

      ... but ... (laughs) And, and I, I don't recall the specific interactions for melatonin. I think that it competes with caffeine so, so anyway, melatonin is metabolized by the liver, by some cytochrome enzymes, I think P450 and there are various other xenobiotics so just foreign compounds, chemicals that are metabolized by that same enzyme and what that means is if you take it at the same time as something else then often the melatonin ends up being broken down far less efficiently than it would be were you to take it by itself.

    17. CW

      So you definitely shouldn't be drinking and melatonin-ing.

    18. GP

      ... it, it's just a weird combination too.

    19. CW

      Well-

    20. GP

      (laughs)

    21. CW

      ... be- be- being frank, you know, uh, if that's the worst thing that the people sat around the table were taking from America-

    22. GP

      Yeah.

    23. CW

      ... it's, it's potentially not, it's certainly not as bad as some of the, some of the stories that you hear coming out. But, so-

    24. GP

      It could be much worse. Yeah.

    25. CW

      ... (laughs) it could be an awful lot worse, yeah. Uh-

    26. GP

      Back, back to melatonin as a sleep aid.

    27. CW

      Yes.

    28. GP

      I, I think that it's useful for helping people to synchronize their circadian systems when the circadian system is misaligned. So jet lag or adaptation to chronic shift work, great. Perfect use case scenario. With very old people, sometimes they experience things like calcification of the pineal gland and, in general, their circadian rhythms become more disruptive, more disrupted at many levels.

    29. CW

      Are we talking s- 60 plus? 70 plus?

    30. GP

      It's, it's like anything else. If you look at the loss of skeletal muscle mass with age or decline in cardio or respiratory fitness, it's, it's a gradual process.

Episode duration: 2:03:10

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