SYSK TRENDING-How Your Circadian Rhythm Runs Your Life

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1:22Have you ever wondered why some days you feel sharp and energetic, while other days it's a struggle just to think clearly, even if you got the same amount of sleep? It turns out there's an internal clock quietly running your life. Your circadian rhythm doesn't just determine when you feel sleepy. It influences your mood, your memory, your metabolism, your immune system, and even when you're most likely to make your best decisions. That's why today's SYSK trending topic is how your circadian rhythm runs your life. So, how does this biological clock actually work, and what happens when we ignore it?

2:03In my conversation with Russell Foster, one of the world's leading experts on sleep and circadian biology, we're going to explore the fascinating science behind your body's master timekeeper and how to make it work to your advantage right after this. Starting or growing your own business can be intimidating and lonely at times. Your to-do list may feel endless with new tasks and lists can easily begin to overrun your life. So finding the right tool that not only helps you out, but simplifies everything as a built-in business partner can be a game changer. For millions of businesses, that tool is Shopify.

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3:48I'm sure you've heard that you have a body clock, that your body works naturally to get you up in the morning and to go to bed at night. It's your circadian rhythm. It's the way humans are wired. Just as some other creatures are wired to be nocturnal and awake at night, humans are wired to be awake during the day. And that creates problems because a lot of us work nights, or we're up late, or we're out at night. And all of this impacts your health, physical and mental. How does that work? Well, meet Russell Foster. He's a professor of circadian neuroscience and director of the Sleep and Circadian Neuroscience Institute at the University of Oxford.

4:30He's also author of a book called Lifetime, Your Body Clock and Its Essential Roles in Good Health and Sleep. Hi, Russell. Welcome to Something You Should Know. Great to join you, Mike. So let's start by you explaining what this body clock is that we have. You can think of it as sort of an internal biological representation of a day. and the exciting thing over the past I suppose 20-30 years is we've got a real understanding of what actually is a biological clock and a whole bunch of genes are identified and the fact that they can be turned on make a bunch of proteins those proteins can form a complex and then go into the nucleus of the cell and turn those genes off those proteins are then degraded and then you have a whole cycle of protein production and degradation and that's in essence what the clock is, and it's all within a cell.

5:25We thought we sort of kind of understood the organization, because there's a structure in the brain called the supra-chiasmatic nuclei, and that was identified as, as it were, the master clock in the brain. And we thought that what happened is that this master clock would force 24-hour rhythms or near 24-hour rhythms in hormone release, in behavior, you name it, on the rest of the body. And then it was discovered that every cell in the body has the capability of generating a circadian rhythm. It has its own clock. And so what you've got is this incredible sort of network of time coordinated by a master clock in the brain, but actually at the delivery end in the organs of the liver, the muscles, the gut, they're actually driving the physiological and behavioral changes.

6:13So we have, in fact, a circadian system, a circadian network in time. And so what's the purpose of it? It's a really important question. And basically, why we have a clock is that we sit on a planet that revolves once every 24 hours. And this produces profound differences in our environment. So we, of course, we have a light-dark cycle, we have temperature, we have, you know, cold, we have availability of food and all the rest of it. And these are profound changes. And what the clock can do is allow us to anticipate this predictable change, 24-hour change in the environment, and fine-tune our biology in advance of the changed conditions.

6:54So before we actually wake up, body temperature is rising, metabolic rate is rising, oxygen efficiency is all rising so that we can deal with the demands of being active. and then at the other end of the day as we settle down towards sleep lots of important things are going on whilst we sleep but we're not active and therefore our oxygen usage goes down our activity levels go down and these are the decreasing in anticipation of sleep so what you've got a clock for is to anticipate these really profound and predictable changes in the environment. There's also another explanation, which is in addition to aligning our biology to the external world, what a clock can do is also align our internal biology so that the muscles, the nervous system, the gut are all working at the correct time relative to each other.

7:54And that's another often forgotten really important role of our circadian system. So does everybody's clock start out the same, more or less, and then maybe it adapts or we adapt to it, perhaps? And some people maybe are more morning people or some people are late night people. Or is the clock set and the clock is set? So we have sort of a bunch of genes, which, of course, we inherit from our parents. and subtle changes in those genes can tend to make us a morning person or an evening person or somewhere somewhere in between so there's a genetic element to whether we want to get up early or get up late there's a second element which is as we age the hormonal changes associated with puberty also seem to interact with with the circadian system so from the age of 10 we tend to want to get up later and later and later.

8:52And this peaks in our late teens, early 20s. And women tend to peak a little bit earlier than men, and men are peaking later, and they tend to, on average, have longer body clocks. They like to go to bed later and get up later. But after the late teens, early 20s, we move slowly to a more morning chronotype, morningness versus eveningness. So by the time we're in our late 50s, early 60s, we're getting up and going to bed at about the time we got up and went to bed when we were 10, 11 years of age. There's also a third really important influence on our sleep-wake, our circadian timing, and that's when we see light.

9:37So dusk light delays the clock, whereas morning light advances the clock, makes us get up earlier and go to bed earlier. And so when we're all agricultural workers, we got symmetrical exposure to morning light and dusk light. So we stayed on cue. We did a study a few years ago on university students showing that those who wanted to go to bed the latest, the more owl-like chronotypes were the ones that were missing out on the morning light, which would advance the clock, make them get up earlier, and got lots of evening, late evening and late afternoon light, which would want to make those individuals get up later.

10:17So you've got three things interacting. You've got your genetics, you've got how old you are, and you've got whether you see light at dawn and dusk. And then I guess you could add into that all the other things from social media, whether you're staying up half the night, you know, looking at your smartphone or doing gaming, which will, in a sense, override those biological drivers of when we want to go to sleep. So when you are staying up all night, maybe you're a shift worker and you work the graveyard shift, are you fighting your clock or does your clock adapt to that shift? No, that's a really important point, Mike.

10:56And the assumption was that if you're working on the night shift, you adapt to the demands of working at night. And studies have shown that 97 % of night shift workers, long term night shift workers have never adapted to the demands of working at night. And so what's happening is your entire biology is saying you should be asleep when you're forcing yourself to work. And that leads to a bunch of problems. One of the ways we can stay awake whilst you know trying to work at night and override this endogenous biology is by activating the stress system and long-term activation of the stress system is associated with a whole bunch of problems such as infection and lured immunity the hormone cortisol the stress hormone cortisol we know that that suppresses the immune system and that predisposes individuals to infection and indeed higher rates of cancer.

11:53What's so interesting is that the World Health Organization has, you know, on the basis of the data has said that night shift work is a probable carcinogen because all the studies showing increased cancer rates in night shift workers. You also get increased metabolic abnormalities such as obesity, type 2 diabetes, and indeed mental health issues such as depression and psychosis. So long-term disruption of our, you know, trying to work while our bodies are trying to make us go to sleep can lead to some serious health issues. That's the long-term stuff. Short-term, we see, and the sorts of things that we've all experienced because we've done a few all-nighters, for example, would be fluctuations in mood.

12:41The tired brain, interestingly, forgets its positive experiences, but remembers its negative ones. And so our entire worldview, if you're tired, is biased towards negative. And that's the basis of what we're making our decisions. Irritability, anxiety, risk-taking, and impulsivity. We do stupid and unreflective things. We tend to show lower levels of empathy. You know, we don't pick up the social signals from friends, family, and indeed work colleagues. And that can lead, of course, to problems, poor memory, impaired decision making, poor communication skills, and a general reduced social connectivity.

13:25And those sorts of problems can kick in after relatively short periods of time, you know, a few days. A few days? Yeah, oh yes. I mean, you get noticeable differences in what your memory, ability to consolidate memory after just one day. It's quite remarkable. We're talking about your body clock, what it does, how it works. And we're talking with Russell Foster. He is author of the book, Your Body Clock, and its essential role in good health and sleep. Pink Panther us here. Coach and Spotify are teaming up to bring music and style together, and they want you to be part of it. Grab your friends and head to the Tabby Tour, hitting cities around the country with live performances from special artists, exclusive experiences, and personalized products.

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14:25Brussels clean up nicely at Sweetgreen. Maple glazed, roasted, and edges perfectly caramelized? Sweetgreen's fall harvest is back on the menu, and the season's most overlooked little green vegetable is dressed to be devoured. You know what to do. Order on the Sweetgreen app. So, Russell, as someone who has worked nights, and I've heard the stories about how working nights or working overnights can cause certain health problems, and I've always thought that part of the problem is that when you work nights and you try to sleep during the day, it's hard to sleep during the day because the doorbell rings, the phone rings, the lawnmowers are going.

15:07There's a lot of disturbances that make it difficult to sleep during the day. So that messes up your sleep, which messes up your health. Yeah, you're right. There are additional disturbances. So when you finish the night shift, you're overwhelmingly tired. And so you've built up a huge sleep pressure. The problem is the body clock has not shifted to the demands of working at night. It thinks it's daytime. So whilst this massive sleep pressure is inducing some sleep, the clock is saying, hang on, it's daytime, you should be up. So the quality and the depth of the sleep that you get whilst trying to sleep during the day is never as good.

15:50And of course, you're much more vulnerable to being disturbed because of noises or light coming in through the windows or indeed, you know, cars outside. So, yeah, it's a real problem. And I guess we have to answer the question, well, why don't night shifters adapt? You know, if you're flying across multiple time zones, you will adapt to the new time zone. and again we have to come back to light and what's happening is that in the workplace whether it be the factory or the office at night you're working under relatively dim artificial light and then on the journey home you're experiencing bright natural light or or later in the day or indeed on the journey back into work and what happens is that the clock always defers to the brighter light signal as being daytime and therefore can never shift the clock.

16:46There are a few examples where the clock has been shifted. There's some experiments were done which exposed night shift workers to bright light in the workplace, you know, 2000 lux or so, and lux is a measure of brightness, and then hid them from natural light during the day. And just like getting over jet lag, they adapted to the demands of working at night because they'd been shifted by the light-dark cycle. The problem is that's just not a practical solution for most people. Well, it's always interested me and kind of gives evidence or credence to what you're saying is when people work days and they're done with work, they typically don't come home and go right to bed.

17:27But when people work nights, they come home and they go right to bed because they've been like, they've been fighting this all night long. And finally they get home and they just crash. Yeah, absolutely. And the sleep pressure is absolutely overwhelming. But the trouble is it can't fully kick in because the clock is saying, no, it's daytime. You should be awake. This idea, this theory that the light determines when we should get up and when we go to bed or should go to bed, then shouldn't we change the time we get up and go to bed based on the seasons? Because, you know, the day is longer in the summer, shorter in the winter.

18:06so shouldn't that alter our bedtime and wake-up time? Yes, in fact, there are very clear evidence showing that as the seasons expand and contract, the length of sleep would change. Now, today we're somewhat buffered from the seasonal changes because, of course, we have indoor light. But in the pre-industrial era, I mean, during the winter times, the period of sleep extended and then it contracted during the summer. So yes, we do adapt to the changing day length over the seasons, and we see differences in how long we sleep. But many of us cannot. We have to get up at the same time and go to bed at the same, roughly the same time.

18:48There's no adapting going on. We have our schedule, and the season doesn't make any difference. That's right. And we're so detached from most seasonal variables anyway. So yeah, we just have to suck it up and get on with it. what's quite interesting is that some beautiful studies by Roger Eker has shown that historically the sleep at night wasn't a single consolidated episode of as we're often told it should be eight hours there's lots of discussion of I had a wonderful first sleep or I had a lovely second sleep and sleep seemed to have occurred in a series of episodes and this is called biphasic sleep, waking up once or twice at night, or polyphasic sleep, which is waking up and then going back to sleep again several times during the night.

19:41And most of us are unaware that this seems to be the default and natural state of human sleep, as in all mammals. And so one of the great problems is that people will wake up in the middle of the night, think, oh my goodness, you know, I'm never going to get back to sleep, start to be anxious, and then, you know, just get up, start doing emails, drinking coffee. Whereas if they would stay calm, maybe stay in bed, but if they're not immediately falling back to sleep, then move to a quiet place where the lights are dim, do something relaxing, they feel tired again, and then return to sleep. And you know, one of the points of writing Lifetime was really to try and get bust some of those myths that you must have eight hours of uninterrupted sleep.

20:26That's not true. So sleep can be, you can wake up and go back to sleep many times across the night. And of course, sleep duration, the length of time we sleep varies enormously between individuals and as we age. The healthy range, as defined by the National Sleep Foundation, it can be from six hours to 10 or 11 hours, depending upon how old you are. So, you know, sleep is like shoe size. One size does not fit all. And the key thing is to try and work out what works best for our particular needs and demands at our particular stage of life. Well, we've been talking as if this is like two things.

21:06It's daytime and nighttime. But what about people like my wife does this? She has to work really early. So she gets up at four. It's pitch black. Does she then suffer some of what you're talking about? Because she's not getting up with the light. And a lot of people, you know, work really early. Farmers, certain shift workers get up way before the sun comes up. That's right. And that is a problem. I don't know how your wife copes with it. But if you're not getting that morning light, and then you're commuting off to work, and then you're sitting in an office building, or inside for the rest of the day, you're not getting that morning light exposure, which is so important to set the body clock.

21:46And what might happen is that individuals who are missing morning light might then finally get home whilst it's light and get that evening light. And of course, the evening light will shift their clock to a later time, making it even more difficult for them to get up early in the morning. And so what I think many of us would advise is that, you know, once you've got up, if you've got to get up at four o 'clock in the morning, then have your breakfast in front of a light box or some other bright light source to try and balance, you know, your light exposure to get that morning light. In the Scandinavian countries, for example, you know, it's even worse where for two months of the year in Tromsø, for example, it's complete darkness.

22:30And many of the families there, they actually have a light box room. So the whole family, when they've got up, goes into this room, sits in front of a light box, and they get artificial morning light, which sets the clock and helps them function, you know, to adapt to the very demands of rest and activity and of course importantly keep those varied 24-hour clocks in the organ systems of the body appropriately aligned. So you had talked about earlier about working nights short-term versus long-term where's the line between short-term and long-term? Yeah I think that's a really good question we don't precisely know I mean we do know that after 20 years you're really sort of likely to have high risk of cancer, metabolic abnormalities type do.

23:22But some people will be more vulnerable than others, and it may kick in much, much earlier. You can certainly get those signs, certainly for metabolic abnormalities, after a relatively short period of time, just a few years. There was a study, though, that published a few years ago, which showed that long-term night shift workers can reduce the risks of cancer and diabetes too if they maintain a rigorously healthy lifestyle. So they're eating really healthy food, so low fat, low sugar, and they're doing lots and lots of exercise. The study was really fascinating because it looked at people over time and really high rates of diabetes too with a poor lifestyle But with a healthy lifestyle, 20 years of night shift work was still a significant problem, but it was much lower than those who didn't lead a healthy lifestyle.

24:21So it's not as though we can't do something about it. We can. When we talk about night shift, I mean, I tend to think of overnights. But what about people that work like four to midnight? Does this same apply? It'll depend. It's a good point. It depends on their chronotype. So if you're a late person, then working from four o 'clock in the afternoon until midnight won't be a problem. Whereas, of course, if you're a morning person, that will be bad. And I think one other thing that employers could do is to chronotype the workers. So, for example, it's easy to do and you could work out whether you're a morning or evening person.

24:58And the thing you want to avoid, of course, is putting a morning person on a 4 p.m. to midnight shift. that's where the late types would probably do okay and you wouldn't get some of the severe problems accumulating and in the same way if you're a morning type then having a shift from 4 a.m. to later in the day wouldn't be so bad for you but for a night person like myself that would be a real problem well I think most people know that there is this circadian rhythm this body clock but I don't think people have any idea how or well they do now but from listening to you but people don't have an idea of how important it is and how much control it has over your life and your health.

25:40So I think it's really interesting and important to understand it. Russell Foster has been my guest. He's a professor of circadian neuroscience, director of the Sleep and Circadian Neuroscience Institute at the University of Oxford. And the name of his book is Lifetime, Your Body Clock and Its Essential Role in Good Health and Sleep. And there's a link to that book in the show notes. It was good to have you here, Russell. It's been really great, Mike. I've really enjoyed talking to you. And that's it for this week's SYSK trending episode, Sweet Dreams. I'm Mike Carruthers. Thanks for listening today to Something You Should Know.