#045 Dr. Matthew Walker on Sleep for Enhancing Learning, Creativity, Immunity, and Glymphatic System

Sleep Optimization: Deep Sleep

Welcome back, my Jedi-level health-o-maniacs. Today's guest is Dr.

"Welcome back, my Jedi-level health-o-maniacs. Today's guest is Dr. Matthew Walker, author of the New York Times bestselling book, Why We Sleep, professor of neuroscience and psychology at the University of California, Berkeley, and director of the Center for Human Sleep Science. As such, sleep is much of this episode's focus, and yet sleep is so important and its effects are so far-reaching that to simply say this podcast is about sleep really doesn't do it justice. It's almost laughably inadequate, in fact. So let's try this again. This podcast is not just about sleep, but the extended biological context surrounding sleep. Not just a list of tips, there's that too, but the why of the sleep, what we know about its function, and maybe as important, the consequences of not getting it. In this whopping two and a half hour podcast, we discuss how pulling an all-nighter decreases learning capacity by up to 40%, how sleep is important for long-term memory because during sleep, we shift memories from the hippocampus, the vulnerable short-term storage reservoir, and we move them out to the cortex, the long-term storage site within the brain. How sounds coupled with certain learning can be used when played at sub-awakening volume to contextually strengthen memories during sleep, a bizarre and fascinating phenomenon. On a similar note, how exposure to odors during learning and then again during sleep can create this exact same selective enhancement of retention. That's right, smells and even sounds can reinforce memories even while we sleep. We also talk about possible explanation as to why we do not remember dreams. Dr. Walker's lab's research showing how loneliness is a type of viral social contagion that is promoted by sleep loss, which was demonstrated by experiments that showed people who were sleep deprived distance themselves from social interactions and were in turn shunned by other people. We discuss how the amygdala, an area of the brain that is important for emotional regulation, is 60% more reactive after sleep deprivation due to a dampening down of the prefrontal cortex function, the effect that genetics plays in anxiety and poor sleep, how the body's fight or flight mechanism is amplified in people who have insomnia, the role of daylight during the day and darkness during the night in improving sleep and circadian rhythms and strategies for using this to our advantage. The fascinating way temperature can manipulate the production of crucial slow wave sleep, which has been demonstrated by changes as small as fractions of a degree. How shorter sleep duration has been shown to reduce natural killer T-cell activity to 70% of normal, which, due to the function of natural killer T-cells, really suggests chronic sleep deprivation may increase cancer risk. How people averaging less than six hours of sleep at night are four times more likely to become ill after being exposed to the flu virus. How poor sleep overall increases sickness rates, impairs glucose metabolism, and even decreases testosterone levels. How the beta cells in the pancreas become less sensitive to high glucose, and other cells in the body become less sensitive to insulin when a person doesn't get enough sleep. The importance of deep, slow-wave sleep, which begins to decline as early as our 20s, ultimately being cut in half by our 50s and declining even more to the point that it's almost undetectable by the time we're in our 80s, according to Dr. Walker. How people deprived of sleep for 36 hours show an increase in the amount of amyloid beta found in their cerebral spinal fluid by as much as 25 to 30 percent, and the crucial role that slow wave sleep plays in helping us clear amyloid beta. Some of the limitations of most sleep trackers when compared to polysomnography, the gold standard of sleep science diagnostics. How people who sleep poorly tend to eat 200 to 300 calories more per sitting than those who sleep well, and overall have a more desire for caloric-rich food, a phenomenon that tracks well with a generalized pro-metabolic disorder quality that is associated with poor sleep and shorter sleep durations. How certain dietary macronutrients may differentially affect sleep. How poor sleep disrupts the gut microbiome. How one cup of coffee in the evening can decrease deep sleep by about 20%, an amount that Matt suggests is equivalent to aging by 10 or 15 years. How alcohol may have a short-lived sedative effect, but it tends to fragment sleep and suppress REM sleep. How ambient-induced sleep resulted in a 50% loss in the learned connections made during the day in a specialized rodent test of neuroplasticity, as well as some of Dr. Walker's other concerns about sleeping pill use in general, and so much more. Before we get this show going, a few quick mentions. Number one, many people often, and I mean often, ask me what my favorite books are. This is a tricky question because in fact, I spend the vast majority of my reading time reading scientific journals. That said, I will eagerly be suggesting Dr. Matthew Walker's book, Why We Sleep in These Situations Moving Forward. Matt is a fabulous presenter, but he's also a really great writer. His book, Why We Sleep, is utterly captivating, regardless of the level at which you're approaching this topic. So seriously, consider pausing the podcast right now and grabbing it from your favorite bookstore just so you don't forget. Number two, in this conversation and also in his book, Dr. Walker presents such a compelling story about the many roles of sleep, especially in learning and memory, but also health, that it's only natural to come to one of the most important conclusions that he specifically calls out, which is that we need to be very vigilant to guard this crucial process from abuses by institutions that should most appreciate its benefits. This especially includes schools, whether we're talking about grade school or high school, or a particularly egregious example addressed in Matt's book, which is the U.S. Medical School Residency Program, which Walker suggests may have some of its roots in emphasis of sleep deprivation, at least partly due to the distorted expectations of a cocaine abusing forebear. An interesting observation, if true. Hey, those were the early days. We know more now, right? No more cocaine and Coca-Cola. Needless to say by now, Matt's a fan of later school start times, and I think this podcast today makes a good case for it. Just something to ponder as we dive in. Number three, while we don't really get too deep into genetics in this podcast, we do talk a lot about circadian rhythm. And it just so happens that circadian rhythm has many genetic components, some of which are tracked by common consumer genetic tests like 23andMe and AncestryDNA. If you've used one of these tests, you can run your raw data through the presently free circadian report found at foundmyfitness.com forward slash genetics. That's foundmyfitness.com forward slash G-E-N-E-T-I-C-S, genetics. We also have a recently improved APOE genotype report, so be sure to check those out. Finally, I want to mention that largely as a result of the generous pay-what-you-can support from Found My Fitness listeners, much like yourself, we continue to roll out great new features. In a long line of great enhancements, this episode comes with a ton of short clips available on our new clips channel over on YouTube. What's that all about, you ask? FMF Clips is a channel dedicated just to breaking out the key moments from interviews into bite-sized formats. That's right, the creme de la creme. These are great for a recap or to evangelize the podcast far and wide to your many sleep-deprived friends. Get those brand spanking new clips by heading over to foundmyfitness.com forward slash clips. That's foundmyfitness.com forward slash C-L-I-P-S. And lastly, if you love what we're doing with the channel, you can join our crew of monthly pay-what- by heading over to foundmyfitness.com forward slash crowd sponsor. That's foundmyfitness.com forward slash C-R-O-W-D-S-P-O-N-S-O-R crowd sponsor. And for real, finally this time, you will note that this podcast starts off sort of abruptly. Sorry about that. The opening discussion is about how sleep patterns change during human development, especially around the age of 12 months when motor skill learning increases. Matt and I were having this discussion and I had planned on doing an intro, but the camera was rolling and the discussion was so interesting that we just kept on rolling. So now, on to the podcast. Really interesting is that if you look at sleep, and we've done some of this work, and maybe we'll speak about it, on sleep and motor skill learning. And that seems to be more dependent on this sort of lighter form of non-realm sleep stage two, and particularly the burst of electrical activity, the sleep spindles. There's a really bizarre bump in stage two and sleep spindles during development. It happens right around the 12-month period, which is where all of a sudden you start to see considerable limb or multi-limb coordination. In other words, you start to perambulate, you start to learn how to walk, it's almost as though there's like a homeostatic response, which is that with the drive for motor plasticity and learning comes a response from sleep to say, oh, now we're into motor skill learning, we need to consolidate. And you get this, it's a really strange bump, and it dies away again after being... What's the spindle, sleep to spindle? What stage is that? Well, you see sleep spindles throughout almost all of non-REM. So once you get past the lightest sort of stage one non-REM, then you get spindles throughout all of non-REM. But they are a prototypical feature of stage two non-REM as well. But then stage three and four, which is sort of like the deep sleep stuff, you also get spindles there too. But in our hands, at least, the strongest sleep stage and the strongest electrical signature in your EEG that is predictive of your motor skill learning is stage two and sleep spindles, both of which seem to have this bizarre sort of, you know, coincidental spike right around this developmental phase of crawling, standing, walking. So many things going on during the development. I mean, it's just, it's so fascinating to observe, for sure. And language, too. I mean, when we've looked at this as well with teaching adults foreign languages, or even actually just mathematical languages or artificial grammar, sleep is a huge component in that. But they also saw this fascinating thing with development, which was about not just concrete learning of individual facts, but the generalization of knowledge. So this is sort of the thing that I think separates us from computers, at least for now, which is that computers are very good at storing individual bytes of information in a veritical way, very clearly. And we can do that too, storing individual facts. But what computers don't do, which is what we do, is intelligently integrate and associate them together so that we can extract overarching patterns and schemas and statistical rules about this thing called the world in which we live. And yeah, sorry, I was just going to say that you can, with infants, you can teach them just these novel sounds, but, and each one of these strings of sounds is unique and different, but there's something common about the grammar that is binding and overarching across all of them."

Sleep Optimization: Deep Sleep

There's a really bizarre bump in stage two and sleep spindles during development.

"Welcome back, my Jedi-level health-o-maniacs. Today's guest is Dr. Matthew Walker, author of the New York Times bestselling book, Why We Sleep, professor of neuroscience and psychology at the University of California, Berkeley, and director of the Center for Human Sleep Science. As such, sleep is much of this episode's focus, and yet sleep is so important and its effects are so far-reaching that to simply say this podcast is about sleep really doesn't do it justice. It's almost laughably inadequate, in fact. So let's try this again. This podcast is not just about sleep, but the extended biological context surrounding sleep. Not just a list of tips, there's that too, but the why of the sleep, what we know about its function, and maybe as important, the consequences of not getting it. In this whopping two and a half hour podcast, we discuss how pulling an all-nighter decreases learning capacity by up to 40%, how sleep is important for long-term memory because during sleep, we shift memories from the hippocampus, the vulnerable short-term storage reservoir, and we move them out to the cortex, the long-term storage site within the brain. How sounds coupled with certain learning can be used when played at sub-awakening volume to contextually strengthen memories during sleep, a bizarre and fascinating phenomenon. On a similar note, how exposure to odors during learning and then again during sleep can create this exact same selective enhancement of retention. That's right, smells and even sounds can reinforce memories even while we sleep. We also talk about possible explanation as to why we do not remember dreams. Dr. Walker's lab's research showing how loneliness is a type of viral social contagion that is promoted by sleep loss, which was demonstrated by experiments that showed people who were sleep deprived distance themselves from social interactions and were in turn shunned by other people. We discuss how the amygdala, an area of the brain that is important for emotional regulation, is 60% more reactive after sleep deprivation due to a dampening down of the prefrontal cortex function, the effect that genetics plays in anxiety and poor sleep, how the body's fight or flight mechanism is amplified in people who have insomnia, the role of daylight during the day and darkness during the night in improving sleep and circadian rhythms and strategies for using this to our advantage. The fascinating way temperature can manipulate the production of crucial slow wave sleep, which has been demonstrated by changes as small as fractions of a degree. How shorter sleep duration has been shown to reduce natural killer T-cell activity to 70% of normal, which, due to the function of natural killer T-cells, really suggests chronic sleep deprivation may increase cancer risk. How people averaging less than six hours of sleep at night are four times more likely to become ill after being exposed to the flu virus. How poor sleep overall increases sickness rates, impairs glucose metabolism, and even decreases testosterone levels. How the beta cells in the pancreas become less sensitive to high glucose, and other cells in the body become less sensitive to insulin when a person doesn't get enough sleep. The importance of deep, slow-wave sleep, which begins to decline as early as our 20s, ultimately being cut in half by our 50s and declining even more to the point that it's almost undetectable by the time we're in our 80s, according to Dr. Walker. How people deprived of sleep for 36 hours show an increase in the amount of amyloid beta found in their cerebral spinal fluid by as much as 25 to 30 percent, and the crucial role that slow wave sleep plays in helping us clear amyloid beta. Some of the limitations of most sleep trackers when compared to polysomnography, the gold standard of sleep science diagnostics. How people who sleep poorly tend to eat 200 to 300 calories more per sitting than those who sleep well, and overall have a more desire for caloric-rich food, a phenomenon that tracks well with a generalized pro-metabolic disorder quality that is associated with poor sleep and shorter sleep durations. How certain dietary macronutrients may differentially affect sleep. How poor sleep disrupts the gut microbiome. How one cup of coffee in the evening can decrease deep sleep by about 20%, an amount that Matt suggests is equivalent to aging by 10 or 15 years. How alcohol may have a short-lived sedative effect, but it tends to fragment sleep and suppress REM sleep. How ambient-induced sleep resulted in a 50% loss in the learned connections made during the day in a specialized rodent test of neuroplasticity, as well as some of Dr. Walker's other concerns about sleeping pill use in general, and so much more. Before we get this show going, a few quick mentions. Number one, many people often, and I mean often, ask me what my favorite books are. This is a tricky question because in fact, I spend the vast majority of my reading time reading scientific journals. That said, I will eagerly be suggesting Dr. Matthew Walker's book, Why We Sleep in These Situations Moving Forward. Matt is a fabulous presenter, but he's also a really great writer. His book, Why We Sleep, is utterly captivating, regardless of the level at which you're approaching this topic. So seriously, consider pausing the podcast right now and grabbing it from your favorite bookstore just so you don't forget. Number two, in this conversation and also in his book, Dr. Walker presents such a compelling story about the many roles of sleep, especially in learning and memory, but also health, that it's only natural to come to one of the most important conclusions that he specifically calls out, which is that we need to be very vigilant to guard this crucial process from abuses by institutions that should most appreciate its benefits. This especially includes schools, whether we're talking about grade school or high school, or a particularly egregious example addressed in Matt's book, which is the U.S. Medical School Residency Program, which Walker suggests may have some of its roots in emphasis of sleep deprivation, at least partly due to the distorted expectations of a cocaine abusing forebear. An interesting observation, if true. Hey, those were the early days. We know more now, right? No more cocaine and Coca-Cola. Needless to say by now, Matt's a fan of later school start times, and I think this podcast today makes a good case for it. Just something to ponder as we dive in. Number three, while we don't really get too deep into genetics in this podcast, we do talk a lot about circadian rhythm. And it just so happens that circadian rhythm has many genetic components, some of which are tracked by common consumer genetic tests like 23andMe and AncestryDNA. If you've used one of these tests, you can run your raw data through the presently free circadian report found at foundmyfitness.com forward slash genetics. That's foundmyfitness.com forward slash G-E-N-E-T-I-C-S, genetics. We also have a recently improved APOE genotype report, so be sure to check those out. Finally, I want to mention that largely as a result of the generous pay-what-you-can support from Found My Fitness listeners, much like yourself, we continue to roll out great new features. In a long line of great enhancements, this episode comes with a ton of short clips available on our new clips channel over on YouTube. What's that all about, you ask? FMF Clips is a channel dedicated just to breaking out the key moments from interviews into bite-sized formats. That's right, the creme de la creme. These are great for a recap or to evangelize the podcast far and wide to your many sleep-deprived friends. Get those brand spanking new clips by heading over to foundmyfitness.com forward slash clips. That's foundmyfitness.com forward slash C-L-I-P-S. And lastly, if you love what we're doing with the channel, you can join our crew of monthly pay-what- by heading over to foundmyfitness.com forward slash crowd sponsor. That's foundmyfitness.com forward slash C-R-O-W-D-S-P-O-N-S-O-R crowd sponsor. And for real, finally this time, you will note that this podcast starts off sort of abruptly. Sorry about that. The opening discussion is about how sleep patterns change during human development, especially around the age of 12 months when motor skill learning increases. Matt and I were having this discussion and I had planned on doing an intro, but the camera was rolling and the discussion was so interesting that we just kept on rolling. So now, on to the podcast. Really interesting is that if you look at sleep, and we've done some of this work, and maybe we'll speak about it, on sleep and motor skill learning. And that seems to be more dependent on this sort of lighter form of non-realm sleep stage two, and particularly the burst of electrical activity, the sleep spindles. There's a really bizarre bump in stage two and sleep spindles during development. It happens right around the 12-month period, which is where all of a sudden you start to see considerable limb or multi-limb coordination. In other words, you start to perambulate, you start to learn how to walk, it's almost as though there's like a homeostatic response, which is that with the drive for motor plasticity and learning comes a response from sleep to say, oh, now we're into motor skill learning, we need to consolidate. And you get this, it's a really strange bump, and it dies away again after being... What's the spindle, sleep to spindle? What stage is that? Well, you see sleep spindles throughout almost all of non-REM. So once you get past the lightest sort of stage one non-REM, then you get spindles throughout all of non-REM. But they are a prototypical feature of stage two non-REM as well. But then stage three and four, which is sort of like the deep sleep stuff, you also get spindles there too. But in our hands, at least, the strongest sleep stage and the strongest electrical signature in your EEG that is predictive of your motor skill learning is stage two and sleep spindles, both of which seem to have this bizarre sort of, you know, coincidental spike right around this developmental phase of crawling, standing, walking. So many things going on during the development. I mean, it's just, it's so fascinating to observe, for sure. And language, too. I mean, when we've looked at this as well with teaching adults foreign languages, or even actually just mathematical languages or artificial grammar, sleep is a huge component in that. But they also saw this fascinating thing with development, which was about not just concrete learning of individual facts, but the generalization of knowledge. So this is sort of the thing that I think separates us from computers, at least for now, which is that computers are very good at storing individual bytes of information in a veritical way, very clearly. And we can do that too, storing individual facts. But what computers don't do, which is what we do, is intelligently integrate and associate them together so that we can extract overarching patterns and schemas and statistical rules about this thing called the world in which we live. And yeah, sorry, I was just going to say that you can, with infants, you can teach them just these novel sounds, but, and each one of these strings of sounds is unique and different, but there's something common about the grammar that is binding and overarching across all of them."

Sleep Optimization: Deep Sleep

I remember this study that was done that was coupling an odor. It was like a cherry blossom odor with electrical shocks.

"But there are people who say that I never remember my dreams. We can bring those people into my sleep center and we can wake them up in the middle of dream sleep and they'll say, it's remarkable for the first time I was dreaming. And the answer is no, it's not the first time that you were dreaming. It's just the first time that you've actually remembered a dream because it's the first time you've typically woken up. My. My mother-in-law, you know, claims that she doesn't dream. And of course I'm like, no, you have to dream. Yeah. There are a selection of patients that have a lesion in a part of the prefrontal cortex in their white matter, which are these big sort of informational fiber tracts that communicate impulses. If you get a lesion deep down there, we do seem to genuinely see a cessation of dreaming in those patients. By the way, I didn't even feel confident to write this in the book, and it's still a theory that I've never really heard in public, but go with me on this, which is I think that we may actually remember all of our dreams or it's possible that there's a tenable theory. The problem is we don't have access to those dreams. Those dreams are memorized and they are available. They're just not accessible. I think what happens as we wake up is that we lose the IP address to those memories. And the reason I believe this to be potentially true is, have you ever had the experience where you wake up and you think, I was dreaming, and I know I was dreaming? And you try as hard as you can, the harder you try, the worse the memory recall goes. And then you think, I'll forget it. Two days later, you're walking along and you see a street sign. And all of a sudden, it triggers the unlocking of that dream memory. You think, oh, that's what the dream was about. As a neuroscientist, that tells me that the memory was present, the memory was available. The problem was accessibility. You couldn't gain recall access. So the information is there. It's just not accessible. It's happened to me just even after I've, you know, when I go to bed, then, you know, later that night, I hit the pillow and all of a sudden I remember the dream right as I'm hitting the pillow. That's happened to me more than once. Right. Which sort of tells you that there is, it's almost a scary prospect, which is that maybe every single one of our dreams throughout life are stored and are present and determine our behavior to some degree. Because we know that there is an enormous amount of information that changes our behavior and our decisions that goes on below the radar of consciousness. Implicit memory. That could be true for dreaming too. And I think I've got an experiment that we may be able to design to actually get at this. And if that's true, it should hopefully radically change our view of dreaming, that dreams are ephemeral, that they dissolve quickly, they're forgotten, and they don't influence us as a human species. That would be pretty groundbreaking. Yeah. You just had a study that I just read, I think, yesterday on sleep and it affecting behavior, loneliness. Yeah. Yeah. So we just published a study demonstrating that sleep loss will trigger viral loneliness. And it was a three-part study. I mean, firstly, the reason that I got into this was loneliness is a killer. We know that there is a massive epidemic of loneliness now in industrialized nations. Being lonely increases your mortality risk by about 45%. In other words, being lonely is twice as risky for your death concern than obesity, which is striking. Yeah. There was actually a study showing loneliness changes a like, a massive amount of gene expression and, like, upregulates NF-kappa-B, cortisol, like, all these pro-inflammatory genes. So it makes sense that they'd be associated with... And what's bizarre about loneliness, by the way, I'm taking a complete...this has got nothing to do with sleep, but if you look at the profile of your gene expression and your immune system, you've got some immune components that will go after viruses. And viruses can only be transmitted from one human being to another by way of touch. They can't live outside of our bodies. Bacteria, so if you scrape yourself on a fence, like, you know, walking past it, you can get a bacterial infection because bacteria can live outside of the body. When you become lonely, your gene expression shifts you away from a profile of immunity that normally deals with viruses and pushes you to more towards a bacterial defense profile. Really? Isn't that incredible? Yeah, you have to study that study. Yeah, that's fascinating. And there's a couple of folks at UCLA who, if you ever have interest in this area of how loneliness, the mind, mood. Oh, totally. Okay, I've got to give you these people. I'm a complete fan of their work. And they did this study, and it just blew my mind. How could a concept that is so sort of, you know, out there, and some people almost don't, you know, believe in loneliness, toughen up, what's wrong with you, go out and make some, how could that change the expression of your genes and even alter how you, the organism, fend for yourself from an immunological perspective, shifting you from viral to bacterial defense. But anyway, so coming back, I was desperately concerned about this state of loneliness. What was interesting, I was reading a lot at the time, because we do a lot of work with sleep and psychiatric disorders, including anxiety. And when I was reading the studies where they would take animals and they would deprive them of sleep, you've got this anxiogenic profile where you've got cortisol increasing, you've got a shift in insulin, glucose regulation, all of the bad things that you would not wish to happen, and anxiety increase. They had fear-like behavior, all by way of just sleep restriction. But what was also interesting is that sometimes the researchers would note, despite not measuring it systematically, that the animals would often be secluded by themselves in the cage, even when they were with other conspecifics. And other conspecifics would not approach them either. And so it seemed to me, just from reading this, I thought, well, this seems like an animal phenotype of human loneliness. And it seems to be caused by a lack of sleep. So we decided we had to do the study. And so the first part of the study, we took a group of individuals, and they went through the study twice. They were either deprived of sleep for an entire night, or they got a full eight hours of sleep. First test was, do you have a social repulsion boundary? And that boundary is increased when you are sleep deprived. So I think everyone has that sense that if I start moving closer to you, you think, OK, do you know what? At some point, that's kind of enough. That's about my close distance. What's interesting is that if I ask a sleep deprived individual to stay put to stay put, and I ask you as an experimenter to walk towards the sleep-deprived individual, and the individual says stop when they feel comfortable, relative to when that very same individual has had a full eight-hour night of sleep, when you're sleep-deprived, you decide to push people a further distance away from you. So you have a lowered desire for social proximity and social interaction. Second, we then replicated that finding, but now we had them inside the MRI scanner because we wanted to see what was changing the brain to produce this social repulsion. What we found was that the regions of the brain that are essentially an alarm network, which is a sort of a stay away from me network that is sort of in the parietal cortex and the premotor cortex. It's sort of what we call the near space network. So it creates your comfort of boundary. And when objects start to approach you, it alarms to say, incoming, be cautious, be wary. That part of the brain became hyperactive when people were sleep deprived. As if you were getting this repulsion signal from the brain. If that wasn't bad enough, the other parts of the brain that have been called the theory of mind network, which sort of helps you understand the intent of other people. It's a pro-social network in the brain. It cooperates pro-social interaction. That part of the brain was shut down by sleep deprivation. So it's a double-edged sort of sword. So we weren't satisfied with that. Next, we wanted to say, could someone who just looked at these sleep-deprived individuals, could they actually judge them as being lonelier and looking lonelier and being sort of perceived as lonely, even though they knew nothing about the experiment. So in the experiment with the sleep deprived individuals, we also did videotaped interviews with them. And we just asked them general questions, tell us about a movie that you watched or what was happening in the news this week, just bland stuff. And then we got 1,000, I think it was over 1,000 people, 1,083 people online."

Sauna: Heat Shock

Then when you look at when they wake up, they typically wake up 15 to 20 minutes before dawn. It's actually the rise of temperature.

"Yeah. I mean, it's an end of two because my husband experienced the same thing. But, you know, there's definitely something there. And what you're saying absolutely happens. The sauna increases vasodilation."

Protein Aggregation Discussion

One of them is a sticky toxic protein called beta amyloid that accumulates in these clumps outside of brain cells, and that creates these amyloid plaques that seem to be correlated with your disease risk...

"So in Alzheimer's disease, there are at least two protein culprits that we believe are underlying the brain pathology that seems to create this thing called Alzheimer's."

Alzheimer Prevention: Prevention

One of them is a sticky toxic protein called beta amyloid that accumulates in these clumps outside of brain cells, and that creates these amyloid plaques that seem to be correlated with your disease risk...

"And so I think that's another area for aging intervention is how can we modulate the circadian rhythm? And it turns out that it comes back to light."

Sleep Optimization: Deep Sleep

One of them is a sticky toxic protein called beta amyloid that accumulates in these clumps outside of brain cells, and that creates these amyloid plaques that seem to be correlated with your disease risk...

"So in the neonatal intensive care unit, what we used to have when we'd go in there, you'd just have constant light on all of the time, dim light on 24 hours a day, which prevented those infants getting the signal of a regulating 24-hour light-dark cycle. if you regularize light in the neonatal intensive care unit. So light during the day, darkness at night, in these studies what you see is basically almost a 50 to 60 percent increase in oxygen saturation within the blood of these neonates in the intensive care unit. Weight gain increases dramatically, and they end up exiting the neonatal intensive care unit about five weeks earlier than they would otherwise. Circadian regulation of sleep leads to better health outcomes. It does so in neonates. It does so in the elderly. So I think there's all manner of sleep possible interventions that we can think about across the lifespan when it comes to modifying disease risk at any stage of life. Yeah. And I think, at least as far as I've, you know, understood from our conversation thus far, some of the main things for prevention and optimizing your sleep really are preventing that emotional stimulation, that anxiety, inducing particularly a few hours before bed, bright light exposure early in the morning, and then not having the bright light exposure, you know, about four hours before bedtime. And then the cold, like having your body temperature go down. So, you know, whether that's through something like, you know, having a hot bath or a hot shower or even possibly the chili pad, which I'm going to actually experiment with. Yeah. Because now I've been using this Oura ring that I've been tracking my sleep. By the way, do you know how accurate, like, so it tells me in my app the light sleep, the REM sleep, and deep sleep. And I know there's nothing going in my brain measuring any sort of brain waves. So it must be movement, right? Yeah, I won't say specifically, even though I know the folks at Aura and I know the folks at almost all of the sleep tracking companies. Most of them right now use a combination of your heart rate, which you can pick up through the pulse waveform, either on the wrist or on the finger, or if it's a bed sensor through the heartbeat, as well as respiration. And they'll use a combination of those things together with movement to try and stage your sleep. Right now, without naming, I don't think there's anyone that is necessarily better than the other. At least none of them have published scientific evidence. We sleep scientists have actually looked at these devices relative to gold standard, what we call polysomnography, which is essentially like doing a sleep study. If you were to, here at my sleep center, we've got all of this equipment. You look like a spaghetti monster with electrodes on your head. I don't know anyone can sleep with that on. Yeah, I know. But we can measure that sleep with high precision, high fidelity. That's the gold standard. And when you compare these sleep trackers, unfortunately, they're not quite accurate. They either overestimate or underestimate sleep onset latency, how long it takes you to fall asleep. They either overestimate or underestimate the amount of time that you've been awake. Sleep duration may not be bad with some of them, a total sleep duration. But once you get into the sleep stages, that's where things become more inaccurate. Their ability to separate non-REM from REM is getting better. It could be in the region of sort of 60% accuracy, possibly lower. But right now, we're not there yet. Will we be there in about sort of four years' time? I actually think we will be. Because that's what I'm really interested in, the deep sleep, obviously. Well, but also I would say REM sleep too. I think REM sleep takes a backseat. It's a bit of a neglected stepsister in the sleep conversation. REM sleep, we found, serves all manner of different functions, one of which is emotional first aid. It's incredible for a palliative emotional benefit. It's not time that heals all wounds, but it's time during REM sleep that provides emotional convalescence. I guess that would also then be important to help you sleep better because if you are managing your emotions better, you probably have less anxiety. Correct. Exactly. But also REM is for the body too. It seems to regulate cardiovascular function. So REM sleep is critical too. Oh, really? Is REM what's important for the lowering the blood pressure? No, it's during deep sleep that you get this lowering of blood pressure. And we've got some data right now that we're about to publish that deep sleep provides actually a homeostatic recalibration of blood pressure. What do I mean by that? If I measure your blood pressure before sleep and then after sleep at a matched circadian time, so we remove the circadian fluctuation of which there is a large one to your systolic blood pressure, but we match it. And so the only thing that's different is the quality of your sleep. What we've discovered firstly is that the amount of deep sleep that you have measured in these big delta slow waves during deep non-REM sleep, that predicts how much of a drop in your systolic blood pressure you will have in the morning relative to the evening, as if deep sleep provides a recalibration of the cardiovascular system. If you're having higher frequency brain waves that are not like the deep sleep, that's what we call unrestorative sleep. If you have a ratio of very little deep brainwave activity and a lot of high-frequency wake-like brain activity, that we call a delta-beta ratio, that predicts very bad cardiovascular outcomes, that if anything, your systolic blood pressure is even worse after sleep than it is the night before. And what we found is that during aging, now we looked at this in healthy people, then we replicated it in older adults, and we found that the older that you get, the less deep sleep that you get, the more sort of wake-like or faster frequency brainwave activity, which isn't good during deep sleep. And that accurately predicts the cardiovascular dysfunction that we see in aging. So we now think we understand in part why poor sleep is linked to poor cardiovascular outcomes. One of the benefits of sleep is that it resets cardiovascular tone and particularly systolic tone. It doesn't stop there. There's lots of other benefits, heart rate drops, et cetera. But REM sleep also seems to have this strange function where you go through these cycles where you get a massive activation of the cardiovascular system, and then it falls silent, and then a massive escalation again. And you get a really remarkable increase in heart rate variability. And heart rate variability has been used as a metric of health outcome, that if you have high heart rate variability, it's very good. It predicts lots of health outcomes. That's what you get during REM sleep. So we should be careful not to think of everything being all about deep sleep."

Gut Microbiome: Diet

You take longer time to fall asleep. The amount of deep sleep that you get is less.

"And it sounds bad and it sounds strange coming from someone like me, but that's better than staying in bed awake for those two or three hours. And over time, gradually by only returning bed when you're sleepy, your brain will relearn the association that it once had when you were a child and you can relearn it, which is that your bed is a place of deep sleep and sound sleep. So that's the next thing. I think the final two things we've touched upon a little bit, which is alcohol and caffeine. Caffeine, many people know, keeps them awake. It's a stimulant. It's what we call a psychoactive stimulant. It's the only psychoactive stimulant, by the way, that we readily give to our children in an unregularized free way which I think is a problem. Caffeine has several problems with it firstly because of it being a stimulant it can keep you awake and it makes it harder for you to fall asleep. A lot of people though will say to me look I'm one of those people who can have a cup of coffee with dinner and I fall asleep and I stay asleep. I'm just fine. Even if that's true, we and others have done these studies. If you give someone a standard dose of one cup of coffee in the evening, 200 milligrams of caffeine, the amount of deep sleep that they have is reduced by 20 percent. You would normally have to age an individual by 10 or 15 years to drop your deep sleep quality by 20%. Or you can do it simply by having a cup of caffeinated drink or coffee in the evening. So caffeine is a problem. The other problem with caffeine is its duration of action. Caffeine has a half-life of about six or seven hours. and a half-life simply means the amount of time it takes for 50% of the drug to still be in your system or 50% of it to be cleared. Caffeine has a quarter life of about 12 hours. In other words, if you have a cup of coffee at noon, a quarter of that caffeine is still circulating in your brain at midnight. So if you have a cup of coffee at noon, it's the equivalent of getting into bed at midnight. And just before you turn out the lights, you swig a quarter of a cup of Starbucks and you hope for a good night of sleep. You know, it's probably not going to happen. So the advice would be try to cut caffeine off around about midday if you can. And even if you're someone who, you know, can fall asleep, fine, stay asleep, you should just know that caffeine can still impact your sleep. It's what usually creates the vicious cycle, by the way, that those people will wake up the next day. They feel unrefreshed and unrestored by their sleep. They don't remember waking up, so they don't think it's the cup of coffee. But now they start reaching for two cups of coffee in the morning rather than one. They've got now more caffeine in the system. The next night they have even less deep sleep. The next morning they wake up even less refreshed. And now they drink more caffeine, self-fulfilling prophecy. Final one is alcohol. Alcohol is probably the most misunderstood sleep aid or sleep drug. It's what most people usually reach for when over-the-counter medications have failed. Alcohol is a sedative. It's a class of drugs that we call sedatives, and sedation is not sleep. So when you drink alcohol, what you're doing is sedating your cortex. You're just knocking yourself out, and that's why you think that you fall asleep faster. There are two other problems with alcohol. Firstly, alcohol will litter your sleep with many more awakenings throughout the night. In fact, some people can even see this on their sleep trackers, even though they're not necessarily as accurate as my sleep laboratory would be. Even with that less accurate measure, you can still see the impact of alcohol and sleep. So it litters your sleep with awakenings, fragmenting your sleep. So this comes back to the third of the four pillars of good sleep, which is continuity. It takes away your continuous sleep and it makes it fragmented. The final part of alcohol is that it's one of the best chemicals that we know for suppressing REM sleep alongside marijuana. Now, by the way, I should say that's THC specific. If you look at CBD, the evidence seems to be less clear. CBD actually doesn't seem to be as detrimental to your sleep as THC. If anything... Yeah, because a lot of people, I mean, again, this could be, this is just anecdotal talk, talk about how marijuana improves their sleep. Yes, yeah. So marijuana, again, we have to separate sort of the active from the inactive component. THC, tetrahydrocannabinol, is the active component. And CBD is the sort of the non-volucinogenic component. But they're both in if people are taking the whole plant. Typically, yeah, yeah, exactly. Now, with strains and drops that you can buy, you can separate those out. You can play around with the ratios, and you can get very low THC to very high CBD. THC does tend to decrease the time it takes you to fall asleep, but it tends to make you sometimes wake up more throughout the night. But it certainly does seem to block REM sleep."

Sleep Optimization: Deep Sleep

Yeah, I would say three to four hours is the time to start thinking about your light saturation exposure, certainly in the last hour before bed.

"And it sounds bad and it sounds strange coming from someone like me, but that's better than staying in bed awake for those two or three hours."