Numlock Sunday: Olivia Walch on the science of sleep
By Walt Hickey
Welcome to the Numlock Sunday edition.
This week, I spoke to Olivia Walch, author of the brand-new book Sleep Groove: Why Your Body's Clock Is So Messed Up and What To Do About It [https://www.simonandschuster.com/books/Sleep-Groove/Olivia-Walch/9781524892951].
Olivia’s a good friend of mine and I’ve been hearing about her research and her work for years, and now she’s finally got a whole book diving into why ideal sleep is more than just the eight hours number we hear so much about. It’s a delightful book with all sorts of cool insights that can have major impacts on your life and health.
We spoke about the human body's numerous circadian rhythms, why sleep regularity is more important than sleep duration, and why permanent daylight saving time is a bad idea.
Walch can be found at oliviawalch.com [http://oliviawalch.com/] and the book can be found wherever [https://www.amazon.com/exec/obidos/ASIN/1524892955?tag=simonsayscom] books [https://www.barnesandnoble.com/w/sleep-groove-olivia-walch/1145929708?ean=9781524892951] are [https://www.booksamillion.com/p/9781524892951] sold [https://bookshop.org/p/books/sleep-groove-why-your-sleep-rhythm-is-so-messed-up-and-what-you-can-do-about-it-olivia-walch/21085327?ean=9781524892951&next=t&affiliate=1688].
This interview has been condensed and edited.
Olivia, thank you so much for coming on.
I'm so delighted to be here.
You are the author of the brand-new book Sleep Groove: Why Your Body's Clock Is So Messed Up and What To Do About It. It's a really, really fun book. It covers a lot of the science behind sleep and actually has some pretty surprising stuff in there for folks who are interested in their own sleep health.
You have a really interesting story about how you even fell into being interested in the science behind sleep. You did a sleep study at some point in grad school that changed your life, it sounds like.
Well, you knew me before then. We were in college together.
Each diabolically bad at sleeping.
I would give each of us a failing grade — you maybe a lower grade than me. I was bad, but you were exploring new horizons of bad, like with polyphasic sleep.
I tried it once. It was such a bad idea.
Maybe a D, D-minus. I knew when I went to grad school something had to change. I was not sleeping; I was not making new memories; I was getting sick. I got MRSA in college and I wonder all the time, was it because my immune system was like a frail Cheeto trying to hold the door closed to the germs? But at the time, I thought at college, you have to do everything. You have to be in every club and miss no opportunity for an experience. And I now remember no experiences from that time period.
In grad school, I decided I was going to sleep more. I did, but I didn't actually notice that huge of a difference with fewer things filling my schedule, even though I was sleeping more. It was better, but it wasn't that much better. It took a sleep study in which I had to keep a really regular bedtime and researchers were spying on me. They would know if I didn't, because I was wearing a device, ye olde Jawbone, which is not even a thing anymore. For months, I went to bed at 11:30 every single night.
The changes were so profound. I didn't just instantly fall asleep at 11:30, though that did happen. I got faster, I lost weight, skin conditions cleared up. In every dimension, my life was better. And the thing that had shifted was not really sleep duration, but sleep regularity.
You get at this idea early in the book. There's this very common number that everybody associates with the right thing to do about sleep, which is that you should sleep for eight hours. The book goes the next level deeper, looks at some of the other dimensions of sleep, and it turns out that eight hours is good, that's a good thought to keep in your mind, but it's really the rhythm. What is the conceit here? Why are rhythms important when it comes to this stuff?
Our understanding of sleep health is so fixated on duration that there's a creepypasta on Reddit that goes, "Oh, these Russians were kept awake and they went crazy." The creepypasta [https://en.wikipedia.org/wiki/Russian_Sleep_Experiment] has always been funny to me because it's like, "Yeah, and after five days of no sleep, they started eating their own organs." (Spoilers for the Russian sleep experiment creepypasta.) Yet we've kept lots of people up for five days and they don't start eating their organs. We have this conception in our minds that losing sleep duration is going to be really bad. It's not good, but it also doesn't make you self-cannibalize after five days of no sleep.
That definition of sleep health is woefully inadequate. The movement in the sleep field is higher dimensional. There are more things that matter to sleep health. There's this big, long list of things. People say you should think about how many times you wake up in the middle of the night, and you should think about how alert you feel during the day.
All of those are great, but they're not memorable. People don't keep two things in their head, let alone five. I'm trying to get people to keep two, which is duration and regularity, as the latitude and longitude of sleep health. You don't say Madrid and New York are close together just because they have the same latitude; longitude also matters. You shouldn't say somebody who sleeps eight hours a night is healthy if they have horrible regularity. That's a case where they are probably pretty far from health, just like New York and Madrid are pretty far from each other.
A lot of this comes down to circadian rhythms. What are they in your view? What kind of bodily processes are governed by them?
The whole shebang. The problem with circadian rhythms is that their UI is terrible. People talk about the circadian rhythm, but that's not really right because circadian rhythms are plural. Sleep is under the subhead of circadian rhythms, but so is everything else in your body: when you're strongest, when you metabolize food, when your immune system peaks, when you repair DNA. There's this real problem. I think that because circadian rhythms are kind of everything, people just say, "You know, the rhythms." This leads to everyone who doesn't study this all day, every day, walking around having no idea what they are and just thinking it's probably the same thing as sleep.
Your body has an internal clock, and it schedules things according to when it thinks you need to do more or less of them. That clock is set by your light exposure, and in modern life, we get light whenever we want it, which is not particularly traditional or natural.
Circadian rhythms developed as a process because we live on Earth, right? We know there's a certain amount of daylight and when certain things should happen, and we evolved specifically to have a circadian rhythm.
Yes. The circadian rhythm is so tuned to Earth that if you put us on a planet with 28-hour days, we probably wouldn't be able to adjust. We would basically continue to have close to a 24-hour period in our rhythms that would continue, even though the sun on this planet would be up and down at different times. It's baked into us, and it's the case that there's just stuff in your body at some times that isn't there at other times. The hormone melatonin, for example. If I made you spit into a tube right now, you would not have melatonin in your spit.
We're speaking in the middle of the afternoon. It's very, very bright outside.
No melatonin. But 10 hours from now? Different story. The thing to imagine is just a bunch of switches in your body getting flipped on and off depending on the time of day, which has massive implications for health, drug efficacy, how you feel, and people have lost their connection to that. Number one, we can have light whenever we want it, so our rhythms are squished relative to where they otherwise would be. But number two, I think we don't have a great way of talking about rhythmic health, which my book tries to address. I'm sure there's much better I can do and other people can do in the future, but this is my first stab at it.
You get at this inflection point where so much of these functions are the result of, if not tens of thousands, then millions of years of evolutionary processes really locking us into a day/night process. Then you have the emergence of electricity, and a lot of your book reflects on how that's actually changed the way our bodies work, in ways we wouldn't ordinarily expect. What are some of those ways?
I would say signs of rhythms having different effects on your body in the winter versus summer. Any study that reports on those, I'm always very cautious about, because I was involved in a study where we looked at Twitter patterns over the course of the year. We wanted to know if people tweeted differently at different times of the year in a way that reflected the sun and circadian rhythms, and we saw this pretty incredible trend where things seemed to really shift around the spring. Daylight saving time is happening then, the sun is changing, so you think, okay, maybe it's related to the sun.
Then we dug a little more closely into the data and saw that the entire effect was just driven by people going on spring break. You would see that people tweeted later when they were on break because they were sleeping in. The fact that we have light available to us whenever we want it and we're not just sitting around in the dark at 6 p.m. in December with nothing to do means that we're in a sort of perpetual summer. We have light as late as we want, as long as we want, and that's stepping on these natural rhythms that would be emerging in the absence of that light.
The title of the book is Sleep Groove, and sleep groove is actually a thing you talk about quite a bit in the book. It's getting locked into a really strong, robust, resilient rhythm, and there are lots of advantages to having that. What are some of the advantages that you have by having that rhythm, and what are some things that can go wrong if you don't?
I would say you die sooner. This is a brand-new result, that sleep regularity predicts dying better than sleep duration, but it does. Again, this definition of sleep health being how long you sleep would say, okay, shoot for eight hours on average, it doesn't matter when, and you're good.
But if you actually look to see what predicts whether you die, the people who have the worst sleep regularity are highly correlated with dying younger, and it keeps coming out. This is in the last 18 months that connections are coming out between sleep regularity and hypertension, diabetes, mood disorders. The data was all there, but people weren't really looking at sleep regularity. We also didn't have as textured tools for defining sleep regularity as we do now, so that's another reason why it's coming out. But things that can go wrong without sleep regularity are all those bad things I listed.
I should say that those are all correlations. You could say, well, maybe stressed people die earlier, and they're also sleeping irregularly as a sign of their stress. Except we also have studies where you put people on weird light schedules and you can watch a melatonin rhythm that's really robust just go away. They go 24 hours without making melatonin, which is weird. You've basically flattened their rhythm altogether.
The mental image I always have in my mind for modern life is that we've taken rhythms that would be really high and pronounced — like, hey, now's the time to fix your DNA so you don't get cancer. Let's fix all our DNA right now. It's really clear period for fixing DNA — and you've stepped on it. Now it's like, well, I don't know. I guess it's the time to fix DNA? Maybe I'll do a little bit of that.
The science is emerging. I don't want to overstate it, but I think there's a strong theoretical case for why the quashing of circadian amplitude is tied to a lot of bad things. The good thing is that more melatonin means you sleep better, feel better — basically my life after doing that one study.
What's a situation where you have a strong circadian amplitude? A lot of light during the day? How do you get there?
You do the same exact thing every day. I should say, I'm going to speak from a theoretical perspective because a lot of the experiments haven't been run yet. It's my collaborators and me who are calling for amplitude to be the new thing we go after, because sleep regularity is just circadian amplitude wearing glasses and a mustache. They pick up the same thing.
What the theory says will get you the maximum circadian amplitude is to have a super bright day and get tons of daylight during the day, and then have a really, really dark night, and copy and paste that over and over again. That's basically it. I'm always think I should add other things for people to do, but it boils down to that.
One of the challenges why people haven't discovered this on their own is that that's actually really hard to do in practice. Light at night is super fun, and we also have to work, and often work is indoors where there's just not as much sunlight.
It really does seem like a problem of modernity. We've always had a way to illuminate the night, for all intents and purposes, but there's a vast gulf of difference between a candle and an incandescent light bulb, and then there's an even bigger difference between an incandescent light bulb and a full room of fluorescent light. There's been this subtle shift that we didn't notice over time, but our bodies did.
You're speaking my language. This is exactly it: the creeping of light into every aspect of our life. Also, because it literally doesn't have mass, it feels immaterial, right? What, the photons are going to get you?
And I don't think they will on a short time span. You can absolutely have a bad night of sleep. You can absolutely have disrupted sleep. People cross time zones. But it does add up over a lifespan, which is why we see sleep regularity being a better predictor of mortality than sleep duration. If you're highly irregular over your whole life, all these rhythms that would otherwise have been high metabolism, high DNA repair, robust ability to sleep, become flat and crappy and you get an accumulation of risk.
So, a lot of what we've talked about is that there are lots of negative things when you're out of that appropriately phased kind of sleep. There are actually some really good things about being very attuned to that, too. You write in the book about athletics, about medicine. What are some of the ways we can actually gain quite a bit through knowing about this?
By having a better sense of what our circadian time is. Conflict of interest disclosure, I do have a startup that tries to do this, but we'll be able to time drugs so that they're maximally effective and as least toxic as they can be.
People sometimes go, okay, timing drugs as in you take sleep medication before you go to sleep. Sure, okay. But what if there were a drug that sometimes made your tumor shrink and at other times made it grow faster? That's a paper that came out in the last year. People aren't thinking about this. They're thinking about a 10% variation over the course of the day. They're not thinking about how this person's glioblastoma treatment didn't work because they took dexamethasone at the wrong time, and they died months earlier.
I think the simplicity of the idea has started to act as a reason for people to not do it. They think, well, if timing actually mattered, somebody would have figured it out already. I won't be the one who wastes a bunch of time rediscovering what everyone else has. My stance is that we're just beginning to scratch the surface of all the things that can be controlled by timing, and the magnitude of the effects we can see.
Imagine the drug I mentioned that accelerated tumor growth sometimes and squished it at others is standard of care. Everybody gets it with this particular type of brain tumor that it was studied in. Imagine you're testing a new drug and oh, it seems to work in these patients but it doesn't work in these other patients. Must not be a very good drug, so it gets ditched. It could be that that entire efficacy difference was driven by when they were taking this standard-of-care drug that everybody takes according to the clock, according to their body's clock. If you could just control for that, you could get more drugs making it through clinical trials.
You even made a point that there's a good shift happening between notes saying you should take this pill in the morning, you should take the pill at night, and changing that to say you should take this pill after waking up or take this pill before you go to sleep. It's getting better at adequately describing the bodily conditions you should take pharmaceuticals under.
Right. If you're a shift worker, you could be waking up at 3 p.m., for instance, and morning could be the worst time for you. You should take it when you wake up. Then again, if you're a shift worker, your rhythms are so funky that — I might be biased here — you should be using Olivia's cool app [https://www.arcascope.com/] to track your circadian rhythms and know when to take all these different things.
But yes, circadian medicine is all about timing your pills before you go to bed or after you wake up. It's also this idea of introducing grooves where we've removed the groove. An example would be that you have a sick kid and you can't feed them, so you put them on total parenteral nutrition, or TPN. They're getting fed through an IV, and the standard for that is to either do it overnight or do it just continuously, 24 hours a day. But if you think about it, if our whole bodies are rhythmic and we expect some things at some times and not at other times, and you're feeding them constantly, that's like being in the light all the time, which we would consider to be torture. If you put somebody in constant light, they are miserable.
These researchers just changed it so they gave TPN only during the day, when the kids are awake and their metabolism is up and running. They were able to leave the hospital on average four days earlier because they weren't being force fed like a foie gras goose overnight. So, it's not just sleep grooves: it's food grooves, it's activity grooves, it's mood grooves, it's all these things. Acknowledging that they're rhythmic will lead to people being healthier.
The medical stuff can get a bit in the weeds, but I thought it was really informative when you talked about U.S. Olympians going to Japan. You reflected on when folks went to Japan and how they trained there. There's actually a lot of performance that was hypothetically not being unlocked because people weren't being attuned to their circadian peaks. Do you want to talk a little about that?
I was reading what people who are Olympians posted on their Instagram, imagining that we were friends. I saw somebody in the weight lifting category be like, "Can't wait to go to Tokyo in two days to compete!" They were fully adjusted or entrained to U.S. time, and they were going to do this trip to Tokyo that was going to massively disrupt their circadian rhythms. Then they were going to compete shortly after landing.
Probably the reason for that is because it's really expensive to go and leave your life for a long period of time, and weight lifting isn't the moneybags, the dollar sign, of Olympic sports. But that probably wasn't the best for optimizing performance, to wait until right before you're supposed to go on and then try and lift something really hugely heavy — though it could have been.
The thing is, when you travel, you get tired and you undergo jet lag because your light exposure is changing, but you also have a circadian rhythm in performance where people tend to do best in the evening. Around 5 or 6 p.m., you're strong and fast and can run far and lift heavy things. If in Japan, you were supposed to compete at 10 a.m., maybe what you want to do is not adjust and be really careful about staying on your old time zone for the first day you're there, so that your body is at 6 p.m. during Japan's local time of 10 a.m.
When it's most suited to compete.
Exactly, to lift a big, heavy thing.
Exciting. You wrote a little about how there are two big peaks for performance over the course of a given day. What are those?
People tend to be alert in the morning, and then they have a second wave of alertness as the day winds down. The way we think about that is that there are two forces that combine to make you feel sleepy: There's how much hunger for sleep you've built up, and then there's your circadian clock basically shaping the gravity. How heavy is gravity for you right now?
In the morning, after you get over this initial wave of grogginess, you have the first wave of alertness and that's because you don't have any hunger for sleep. Imagine you're biking, and you just started biking so you're feeling fresh, you're okay. You haven't accumulated feeling tired from biking. In the middle of the day, though, you have accumulated some fatigue. You've been doing stuff with your brain and the circadian clock is not saying it's a great time to be alert. People often get sleepy in the middle of the day, like you would be sleepy if you'd been biking for four hours.
Then later in the day, the circadian clock comes in and says it's time for you to be awake. You need to get your act together before the sun goes down or you might die. That's like the road you're biking on sloping downward. It becomes easier. It doesn't take as much effort to stay awake; it doesn't take as much effort to pedal. Your circadian clock is like, great, be alert. Do stuff in the latter part of your day up until close to your habitual bedtime, when the road starts to swoop up again.
Then you basically hit the wall of, it's 3 a.m. I want to die. Why am I staying up super late in the year 2009 next to my good friend Walter? What are we doing? You push through that and you get on the other side, and the road starts to slant down again.
It was really cool to see, because this speaks to my experience of being sleep deprived and going over the swing set. It's really cool that circadian rhythm still holds, and that's why you get that second wind in the morning and sleep deprivation madness or whatever you want to call it. You do still see that swing hold even if you get more and more sleep weight accumulating.
Exactly.
I want to talk about some of the studies that you covered, because they're very, very interesting, but I also want to talk about some policy implications. Two things stuck out to me. One was the conversation about daylight saving time and potentially going either permanent DST or permanent standard time. The other one that was super interesting was basically how teenagers react to light and how we set school schedules. What are your insights on those two potential policy questions?
Let's do DST first. This also has horrible UI. Nobody can figure out what they're saying when they talk about DST. So, standard time is brighter mornings, darker evenings. Standard time is what we're on in the winter when everyone's depressed and they're like, "It's 5 p.m. and it's dark. Stupid, stupid DST." That's actually standard time that's causing that. DST is darker mornings, lighter at night. DST is what we're on in the summer when we have lots of light even at 9 p.m. It's really bright at night.
The thing most circadian scientists are going to tell you is that permanent standard time is best, then the current system where we switch, and then the last and least preferable is permanent DST. You might think, okay, but why isn't it just better to not switch? There's this penalty of everyone jet lagging themselves when we wake up an hour earlier or have to stay up an hour later when we do these transitions in the spring and the fall. The reason is because having the light late into the day in the summer, and especially having light in the afternoons and evenings in the winter and really, really dark mornings in the winter, is worse than the jet lag from transitioning. If we did permanent DST, where we have really dark mornings in the winter, it wouldn't just be a couple days of us all feeling jet lagged. It would be this chronic buildup of a messed up groove.
One of the reasons why it's hard for people to concisely say why permanent DST is bad is because it's about rhythmic health. It's been argued, hey, if you want to maximize the amount of hours that we have really bright light during the daytime periods where people are normally awake, DST is really good for that, because you have light until super late. Think about the summer.
But do we want to maximize that?
Exactly, because imagine the case that I alluded to when we were talking about the meal timing thing. If you're in bright light 20 hours a day like people are up in the Arctic, you have bad sleep. It's not because you don't know about blackout curtains; it's because you're not able to adjust to a rhythm that's all bright light, little bit of darkness. What permanent DST does is basically, in the wintertime, it forces a bunch of people to wake up in darkness, or dim light. They then stay in the dark for a really long time, and they get their bright light weighted way on the latter half of their day.
I'm going to go into a long analogy, but I promise I'll bring it back down. Imagine a sidewalk with alternating yellow and black squares, and I give you a yellow shoe and a black shoe. I say, yellow shoe steps on the yellow square, black shoe steps on the black square. If it's well sized to your legs, you could just do that. You're like, awesome, this is great. But then I do something where I basically take the yellow squares and scoot them up into the black squares. Then I have this brownish, crappy blurring of light and dark: yellow, black, and the blur. If I go, "Okay, walk on this," what you have to do is take one big step with one foot and a little step with your other, and you have to repeat that over and over again.
That's basically what DST is doing to you in the winter. If we were to go to that in the winter, you'd wake up in the darkness, but then you'd get light later in the day. It makes it so that your rhythms are thrown off. You wake up with a bunch of melatonin in your body. It's like everybody's popping melatonin pills first thing, if you were to do permanent DST.
If you're sitting here thinking, "I'm not convinced by her arguments around stepping on yellow tiles with yellow shoes and black tiles with black shoes," the most compelling reason is the fact that we literally tried this. We tried DST in the winter. We didn't even make a year. Russia tried it in the last decade — they made it three years and they bailed. People have tried DST in the winter and we all think it sucks. Meanwhile, Arizona has been on standard time all year since the 1960s and they're going strong.
They seem really thrilled with their situation in Arizona.
They're pretty happy. So, moral of the story, the current system would be better than having super dark mornings in the winter, which is what permanent DST would be. But I don't really care that much because I'm so convinced that if we try this again, we'll be like Russia in 2014 and bail. We'll be like us in the '70s and bail. We just need to, as a generation, collectively experience it and realize, oh yeah, this is why DST sucks.
The old knowledge has been lost. We must relearn it.
We'll relearn it and we'll say, no, we're never going to make this mistake again. And then in 50 years, we'll make it again.
People always want the optimization of, I want more sleep. I want eight hours of sleep. I want the most sleep I can possibly get, or I want the most light I can possibly get. It seems like that's a trap. I completely understand why people get into that position, because I like light and I like sleep, but just realistically, if you're seeing how much of this governs the rhythm of lots of different processes that are more sophisticated than just enjoying seeing bright things, it's a real shock to the system.
Human brains are just not wired to think rhythmically. It's like if you're in a math class and you're learning about Fourier series, to go extremely niche, really fast. It's not intuitive. People are wired to think, "More of thing good," and we're just less wired to think, well, it's good at some times and bad at other times.
Very briefly, then, should kids be going to school as early as they currently go to school?
No. At the same time, we also shouldn't make it so late, because what would happen if we made it really late is kids would just stay up later. There are diminishing returns, but now you have kids who are waking up at 5:30. That's absolutely what it would feel like for me to wake up at 3:30. It's cruel to them. There's this idea that, oh, we'll do DST. We'll do permanent DST so we don't have to switch, and then we'll also make school times an hour later.
You've basically just got us back to where we started. You've made it so that they're going to be functionally popping a melatonin pill in the morning, just based on how much more melatonin is in their body when they wake up, and then you're letting them sleep in another hour. You cannot make both of those changes and act like you've changed anything. You at best maintain the status quo. My personal vote is we should do permanent standard time or keep the current system and make it so that schools for kids start later.
The book is full of really, really interesting studies. Some of them are fascinating, recent, breaking studies that, like you mentioned earlier, reveal incredible things about the link between these biorhythms as well as pharmaceuticals and things like that. Some of them, however, are from a more swashbuckling age of discovery, and you cover a lot of really interesting sleep studies from the earliest days of sleep research. Do you have any favorites?
In the book it probably comes across that I am so enamored with these old sleep studies, in part because they really underscore this point that if our definition of sleep health is only duration, it's insufficient. There are a bunch of peer-reviewed papers that went, yeah, this guy said he didn't want to sleep anymore, so he just didn't sleep for a week and we watched him. Actually, that's maybe my favorite. There's this guy who comes into a lab and is like, humans don't need to sleep and I can prove it. And then he just doesn't.
They went, whoa, let him cook?
Yeah, he might be on to something. In the paper, they're like, we tried to stop him but he said he was going to do it anyway, so we gave him a typewriter to see how bad he got at typing. The answer is, he got so bad at typing so fast that he just went, I can't do this. They didn't make him type anymore because it was too hard for his eyes. He got really snippy. People tend to hallucinate when you keep them up all night. They get paranoid for days and days. But at the same time, he was functioning. He was able to, on the last day of the study, write a vaguely sexist acrostic poem. I have tried to understand this thing. It's confusing, but you get the sense that it's not positive toward women.
The original no-sleep creepypasta.
Seriously. Obviously, I'm glad we don't do studies like this now. We have human subject protections. Why would you need to run the study? They did that in the '30s and '60s, and it was weird. But the data's been out there for so long. The creepypasta levels of sleep deprivation, people can survive. You should not do it. You should absolutely not do it. It's a bad idea. But it's not an instantly fatal thing, like you pulled an all-nighter so watch out.
The punchline is, unfortunately for human brains, which want very rapid feedback and instant gratification, the way to have sleep health is not something acute, like the absence of these all-nighters that are terrible for you, but rather the constant maintenance of healthy rhythms that are on the time scale of weeks, months and years, as opposed to hacks that you can do in one hour of your day.
The book is called Sleep Groove: Why Your Body's Clock Is So Messed Up and What To Do About It. There are so many fascinating things in here, Olivia. Why don't you tell readers a little about where they can find the book and you.
Sleep Groove [https://www.simonandschuster.com/books/Sleep-Groove/Olivia-Walch/9781524892951] is a book about the emerging science of sleep regularity and how it matters so much to your overall health, well-being, and how you feel at 3 a.m. in the morning. You probably feel pretty bad; my book will explain why. You can find it where books are sold, including Amazon [https://www.amazon.com/exec/obidos/ASIN/1524892955?tag=simonsayscom] and your local independent bookseller [https://bookshop.org/p/books/sleep-groove-why-your-sleep-rhythm-is-so-messed-up-and-what-you-can-do-about-it-olivia-walch/21085327?ean=9781524892951&next=t&affiliate=1688]. There's also an audiobook coming out next month.
Oh, fun. That's great. Thanks so much for coming on, Olivia.
Thanks for having me.
Edited by Susie Stark.
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