[00:00:00] We are on day seven of our 12 days of Christmas. We have probably lost track of time. We dunno what day it is, let alone what time it is. But what we are hoping for is to catch up on some sleep. In this episode, professor Russell Foster breaks down the science of sleep and why poor sleep quality undermines decision making, metabolism and mental health from the dangers of self-medicating with alcohol to the myths around catching up on sleep, Russell explains what's really happening in the brain when we don't rest properly.

This is a clear evidence led conversation about circadian rhythms, morning light, anxiety, and simple interventions, including when a short nap can genuinely improve cognitive performance.

Juliet Fallowfield: Thank you Russell so much for your time today. It's great to have you on have startup. It'd be wonderful if you could give a bit of a background as to who you are and your profession. 

Russel Foster: Well, I'm really delighted to join you. I'm Russell Foster. I'm professor of Circadian Neuroscience at the University of Oxford.

And I'm the [00:01:00] director of the Sleep and Circadian Neuroscience Institute, and I'm also head of the FEL Laboratory of Ophthalmology. And for almost 40 years now, I've been working on how circadian rhythms and sleep are generated, and particularly how they're regulated by light. And more recently, it's been taking that fundamental science in place.

It. Placing it into a sort of a translational context. So the fundamental science is now being applied to the health sector and a variety of other sectors too. 

Juliet Fallowfield: And we should also mention, you've written an incredibly interesting book about the subject, and given that not just business owners or founders sleep, everyone sleeps and everyone breathes, and everyone needs to drink water, but sleep is such an important part.

If you, I, is it even possible to explain why sleep is so important to us? 

Russel Foster: Well, I think for so long we've marginalized sleep. We've sort of thought of it as this. Luxury or indulgence. And in fact, those of us who remember the eighties, people would bounce in and [00:02:00] say, oh, I've done another all night. You know, aren't I great?

As if sleep was some sort of an illness that needs a cure. And what's really happened, I suppose, over the past 20, 30 years is we've realized that sleep isn't. Absolutely fundamental and essential part of our biology. The quality of our sleep defines the quality of our wake and our consciousness. It defines how we interact with other people.

It defines our sense of humor. There's so much that it does, and it is not an indulgence or a luxury, and we need to embrace it and find ways of embracing sleep. 

Juliet Fallowfield: I think this is something I've learned the hard way that when you start a business and you're doing something for the very first time, in fact, 90% of your day is inaugural.

It's the first time you've ever built a website or worked out your payment terms or tried to invoice somebody or find a client. Time is precious. There are 24 hours in our day that have been talked to us. That 24 hours is the, the day and the seven days in the week. You as a new founder, tend to go [00:03:00] and go and go and go and go until things are done, but then realizing things are never done.

Why should we factor in a time allowance for sleep in that working day? 

Russel Foster: Yeah. I think it's so important, particularly when setting up a business. So I think we've, we've kind of defined sleep on the basis of what happens you if you don't get it, and, and perhaps that's a good way of thinking about it. So short term loss of sleep.

Leads to sort of fluctuations in mood and what's called a negative salience. And I think this is so fascinating. Wonderful experiments have have shown that the tired brain remembers negative experiences, but forgets the positive ones. So your whole decision making machinery is going to be biased towards the, the negative rather than the positive.

You show increased. Irritability and anxiety, you have a loss of empathy, so you fail to pick up the social signals from friends, colleagues, potential clients, and you show high levels of frustration and you exhibit that frustration, which of course is not good [00:04:00] within the business sector. You, very importantly, you tend to indulge in more risk taking.

And impulsivity. One level, it's, oh, I think I can make that red traffic light. Whereas in fact, you would never do it if if you weren't tired. Mm. But of course, in the business sector, it means that you may expose yourself to situations because you've done stupid and unreflective things. You tend to use stimulants and then sedatives, so you can drive the waking day, overriding the effects of tiredness by endless cups of caffeinated drinks.

You get to the evening and think, oh God, I ought to get some sleep at this point. And then you'll try and use a sedative and that may be alcohol and so many people fall into, yeah. The stimulant driven and sedative alcohol driven sort of sleep wake cycle. And the key thing about sedatives like alcohol, like sleeping tablets, is that they're sedatives.

They do not provide a biological mimic for sleep. So some of the important stuff going on. [00:05:00] Memory formation. Our ability to come up with novel solutions to complex problems are actually impeded by taking sedatives. You can also find with more than just a few days, you start to build up some problems and that, and that can of course build up over weeks and months so you can have daytime sleep.

And that's not great. Micros sleeps, I think, is really important because this uncontrollable, falling asleep. Now, if you're driving, that can be literally fatal. A hundred to 300,000 crashes on the American freeway have been linked to people just simply falling asleep at the wheel. Then with months of sleep deprivation, then you begin to be more vulnerable to cardiovascular disease, altered stress responses, altered immune responses, and of course.

Metabolic abnormalities, uh, uh, I think are, are so well described. So the, the slide into type two diabetes, the distortion of the metabolic axis. If you're [00:06:00] tired, you are throwing the hunger hormone into the circulation, and so you're eating more sugars and carbohydrates. One study looked at healthy young males with only four hours of sleep, uh, versus others, which were, who were allowed to sleep up to 10 hours and after just one week.

The hunger hormone ghrelin had gone up by, I think something like 27%. The, the satiation hormone leptin had gone down by something like 14%, but carbohydrate consumption just after a week had gone up by 35 to 40%. So not getting the sleep that you need can distort the whole metabolic axis. 

Juliet Fallowfield: So it's a vicious circle and you are doing more and more and more and more damage and it's cumulative.

Yeah. 

Russel Foster: And if you are vulnerable, then the slide into depression and psychosis can occur. Some work that we've done here in Oxford has shown that the clear links between sleep weight disruption. Sleep and circadian rhythm disruption, something I might use the, the shorthand scarred. I know it sounds like bon villain [00:07:00] and if you have scarred then the severity of your mental, we studied paranoia, hallucinatory experiences had gone up so.

I think the key point would be that if you don't get sleep, there are the short term sort of consequences in our cognitive and our emotional responses. Longer term, you are really opening up some potential health issues and I think it illustrates the fact that not getting the sleep that you need and we should talk about that, is so much more than feeling tired at an inconvenient time.

It has a big effect upon our, our global health and our ability to function. 

Juliet Fallowfield: So really it's mandatory in anybody's life, but when you're starting a business, you will be a better business person if you look after your sleep. 

Russel Foster: I think that's right. Now, clearly short term, the need to get that paper written or that report done short, we, we all distort the system, but it's where it's sustained.

That's so as problematic and I think one needs to be aware that okay, right, I've done that. [00:08:00] Sort of near all nighter. 'cause I had to get that project done. That was the deadline. The next day I'm gonna be really careful about my interactions, what I'm gonna take on and I'm gonna try and actually step back.

So it's all about checks and balances. 

Juliet Fallowfield: And given we are all different, you say how much sleep you need, how does one find out their personal sleep? Allowance. 

Russel Foster: I think this is so important. Really a really a fundamentally important point. And it's part of the reason I wrote the book 'cause I was absolutely fed up with the sort of sergeant majors of sleep screaming, you must get eight hours.

And it was terrifying people. I had one chap who came up to me and said, I don't get eight hours of sleep. Am I going to die? And I said, whoa. 

Juliet Fallowfield: We, we all are, 

Russel Foster: yeah. I can guarantee you're gonna die, but it may not be linked to that. And so people have become very, very anxious about it. It doesn't help you get a good night's 

Juliet Fallowfield: sleep.

Russel Foster: It really doesn't. It may, in fact, most people don't have a sleep problem. They actually have an anxiety and a stress problem. Mm-hmm. Which prevents them [00:09:00] getting the sleep they need. So how much sleep do you need? Well, it's not rocket science. If you are feeling as though you're able to function and you are working optimally during the day, you probably have the sleep that you need.

But if you're dependent upon an alarm clock or somebody else to get you outta bed in the morning, that's probably means you're not getting enough sleep If you oversleep extensively on free days. And particularly when you go away on holiday, and in fact, even though you are setting up a new business, it is important to step back and go away on holiday.

Mm-hmm. But you can see that your sleep will expand hugely. And, and people often use the weekend, for example, for catch up sleep. It's not a good strategy. It can partially help, but it can actually distort your sleep. Wake cycle means that the Monday is, is actually a sort of disrupted. 

Juliet Fallowfield: We talk about circadian rhythms and I was reading that it's about a day.

Yeah. Deer being day and psycho being about, yeah. Should we be in sync with our environment? Yeah. So if the sun's coming up and we're waking up naturally with the [00:10:00] sun and the sun's going down and we are going to bed naturally with the sun going down, is that a good rule of thumb? 

Russel Foster: So. We have this internal clock, these circadian rhythms, and they run in humans.

On average, about 90% of us are a little bit longer than 24 hours. So if we went to a deep, dark cave, no light and constant temperature, we get up with respect to the outside a bit later, and later and later each day. What that means is the internal clock needs to be aligned to the external world, and for most of us, the exposure to the light dark cycle is so critically important, but light has different effects at different times.

So morning light advances the clock makes us get up a bit earlier. And go to bed a a bit earlier, whereas dusk light means we'll go to bed a bit later and get up a bit later. And so if you have a clock, which is drifting later, and later and later, it needs a daily advance. That's why morning light is so important, because it's [00:11:00] the morning light that advances the clock, and the evening light delays the clock.

Juliet Fallowfield: So just to recap, you should really, as an individual, keep an eye on your sleep patterns. Yes. And I know in your book you have an amazing appendix that will do a survey as to find out who you are and how you operate. And then really sort of, I guess, agreed with yourself that I am a nine hour person and it's mandatory.

Yeah. I will operate better. That's right. And more efficiently, and my business will be stronger for it if I do that. Throughout the week and not stockpile at the weekends. 

Russel Foster: Yeah, absolutely. And, and of course by trying to override this sort of really fundamental deep biology, we set up all of our, our health problems.

Juliet Fallowfield: Amazing. And talk a little bit more about naps. 'cause you mentioned that they are a thing or should not be a thing. Maybe. I'm not sure. 

Russel Foster: I have mixed views about naps, so. First of all, if you need a nap, it means that you probably didn't get all the sleep that you needed the night before, which, you know, okay, uh, but, but the occasional nap I don't think is a problem.

The data suggests that a short nap of [00:12:00] 20 minutes is good and it can improve midday, for example, improve your cognitive abilities and your efficiency later in the day. If you sleep for longer than than 20 minutes, you might go into a deeper. State of sleep and recovery from that can leave you sort of a bit, sort of muggy.

So if you're gonna have a, a nap, then you know, set an alarm for for 20 minutes or so. Where it becomes problematic is that if you get very short, nighttime sleep. You then get up or you're driven outta bed and then you struggle, and then you fall asleep later in the day, and that's fairly close to bedtime, which then pushes back the pressure for sleep, which means you're not having a nap, you're having a one or two hour sleep, which means you are delaying sleep that night.

Which means that the opportunity for sleep is diminished, which means you're gonna feel tired the next day and you might fall into the trap of longer naps and shorter nighttime sleep, [00:13:00] and that should be avoided. Now, one of the things that's turned out to be very interesting is that the default pattern of human sleep is not a single.

Eight hour or nine hour or six hour block, but it can be called polyphasic, which means, or biphasic, which is you fall asleep. You then wake up. Sometimes you're aware, you've woken up. Sometimes you won't be, you fall back to sleep again, and you can have several epi episodes of waking and falling back to sleep across the night Now.

The problem that many of us have is that if you're anxious or stressed, and if you're setting up a new business, this is sort of embedded in your, what, you know, your thoughts, um, 

Juliet Fallowfield: can happen. Yeah. 

Russel Foster: Yeah. Then you wake up and you think, oh, what, what all the stuff, and you can't then fall back to sleep, and, and I think it's very important that.

People know that this is, it's fine if you wake up, you just need not be the end of sleep. Stay calm. You may want to leave the sleeping space, leave the bed, keep the lights low, [00:14:00] maybe read a favorite novel. I remember saying to somebody, you know, um, well, a few pages of Jane Austen or something, and they came back to me at the end of the talk and they said, does it have to be Jane Austen?

I said, no, no, no. Just something that you find relaxing and then you will feel tired to get in and go back to sleep. 

Juliet Fallowfield: So not a screen, not a phone. Don't read on a phone. 

Russel Foster: Well, the data there are mixed. Ah, you'll read sort of in the media some banner headlines that looking at a a, a Kindle before you go to sleep, for example, um, is it will shift your biological clock.

Well. 

Juliet Fallowfield: They don't have blue lights, do they? 

Russel Foster: Blue light is, there's, there's almost no data at all saying blue lights are having an impact upon sleep versus, uh, it's all about the light intensity. That's the most important be because what, what the receptors do, they have a, a, a bell shaped response. So it's not that they won't absorb other.

Colors, other wavelengths. It's just that they're less li less likely to do it. They're maximally sensitive. These, these receptors that regulate our [00:15:00] sleep wake cycle and our circadian rhythms in the blue part of the spectrum, these are the, the receptors we discovered. But, but they also will, will absorb other wavelengths as well.

And if it's bright enough, it really doesn't matter what. So, you know, these, these screens that shift from blue light to to red light. The evidence that they actually have any impact is almost non-existent. 

Juliet Fallowfield: So just if, if you're waking up in the, like read something with a dull light. 

Russel Foster: Yeah, exactly. And so the Kindle study, which I think is so interesting, they got people to look at a Kindle.

On its brightest intensity for four hours before sleep over five days, and at the end of that period it delayed sleep onset just statistically significantly by 10 minutes. And as one of my colleagues said, well, it might, might be statistically significant, but that's biologically meaning. 

Juliet Fallowfield: Waking up in the middle of the night, you're like, no, I need my sleep.

I've gotta get up early 'cause I've got a big day ahead. 

Russel Foster: Mm-hmm. 

Juliet Fallowfield: Try not to panic. Exactly. Read something, it'll send you back to sleep. Yeah. And are there any other techniques that you [00:16:00] advise? 

Russel Foster: Oh yes. Most people will have some sort of an alarm clock by the bed. If it's an illuminated one, what's the first thing you do?

You look to the side, you think, oh my goodness, I've only got two hours before the alarm clock goes off. And then you say, oh, might I just, you stop drinking coffee, you know, doing emails and, and of course. It doesn't matter that you've only got two hours. Actually, you know, people get huge advantages of 20 minute nap.

So why are we dismissing that two hours of as additional sleep that you could have before the alarm clock goes off? So what I suggest is actually just cover the face. Don't look at the time. Don't look at the time. It's when the alarm clock goes off. That's important, not how long before it goes off, so you can get completely stressed out by 

Juliet Fallowfield: it.

I always try and set an alarm, have to. That's up to that. But to get to the gym, to be in a bit more of a structured day and try and have as many days I get up at the same time every day. Yeah. Um, I try, if I have a late night for work or I wake up in the middle of night, should I then let myself sleep in or should I stick to my schedule and then try and get back on.[00:17:00] 

Russel Foster: Try and stick to your schedule. Yeah. Try and get stick schedule, particularly if it's things like the gym. And try not to exercise too late in the day though, because. Part of sleep initiation is a small drop in core body temperature, and if you block that, that drop in core body temperature, it could be more difficult to get off to sleep.

And so, so if you're exercising very vigorously prior to bed, that can actually delay sleep onset. And also you're gonna be, you know, releasing all of those neurochemicals, which, which have an alerting effect upon the brain. So, evening is fine, but just not too close to bedtime. And 

Juliet Fallowfield: diet, does that have an effect on sleep?

Russel Foster: Yeah, it's really fascinating and some new data coming out on this. So in 1100, the main meal of the day was breakfast. That's when the big meal. But by we get to two times, it's the main meal of the day has, has moved a bit later. So it's about noon, but with. Advanced industrialization where people were commuting from their home to the [00:18:00] workplace.

And then back again, it meant that they didn't have much time in the morning for a decent breakfast, and they probably were pressurized at work, so they didn't have time for a decent lunch, uh, particularly in, in the, in the last few decades, uh, where the, the big lunches sort of evaporated and then you'd finally get home and you'd.

Stuff, something in the microwave, um, which, uh, would be your main meal of the day. Now what's been shown is that the circadian system really regulates our metabolism and the same meal at breakfast time, lunchtime in the evening, the levels of blood glucose, which of course can be a predispose to metabolic abnormalities, metabolic syndrome, uh, type two diabetes.

And indeed obesity is cleared effectively in the morning at lunchtime. Not cleared later in the day. And if you think about it, our metabolism is profoundly different. We're we're taking in calories during the day and we're burning those up to, to, [00:19:00] to be alive. Um, and then of course, at nighttime we're not taking in calories.

We're mobilizing the calories that we've stored. And so, uh, our metabolism, metabolism is completely different. And so the closer we eat to bedtime, the more likely we're gonna take those calories and store them and not burn them up. So you are more prone to, as I say, um, metabolic syndrome type two diabetes and obesity.

And of course all of the, the health consequences of that. So if you can, we should be defaulting back to a more sort of breakfast, lunchtime, main meal of the day. Really a light, a light supper. 

Juliet Fallowfield: I notice if I go to bed earlier and get up earlier, so it could be in bed by half, by 10, and up at five 30. I am a very much improved human being.

My team notices it. I notice it. I get a lot out of my day. I feel more efficient. Yeah. Even if I get the same amount of sleep, if I go to bed at midnight and get up later, why is there a difference there? 

Russel Foster: Oh, it's because of our [00:20:00] fundamental biology. It's basically the way our clock works, the way we respond to sleep pressure.

There are two factors regulating our sleep. One is the clock, which basically says, now is the time to be awake. Now is the time to be asleep. But then from the moment we wake in the morning, chemicals build up in the brain. Substances like adenosine, uh, build up in the brain, and they provide what's called sleep pressure.

So what happens is that the sleep pressure builds up and up, and up and up and up during the day. You don't fall asleep, ideally because the clock is saying, stay awake, stay awake, stay awake. And the clock's drive for wakefulness, ironically, is at its highest. Just before we fall asleep, because you've got the sleep pressure, which is really high.

The clock is saying, stay awake. Stay awake, and it says, okay, now it's time for sleep. The clock kicks in for going to sleep. The sleep pressure is really high, and then you fall asleep. So you've got these two systems interacting and they're very variable between individuals. We've talked about your chronotype.

I'm guessing that you are probably [00:21:00] more of a lark than an owl, and therefore. Going to bed early and getting up early works for you and you should protect that. 

Juliet Fallowfield: Yeah, protecting it. That's the key. And what we are doing with this season about health and wellness with all founders and experts, the previous guest has a question for you, the next guest, and I see, so the previous question was, what was your biggest leadership challenge?

Russel Foster: I remember one case where we had a PhD student and this individual just wasn't up to it. And of course. What we do as I think as mentors, you know, you want to get the best outta people, you want to support them, and it was quite clear that this person was not going to get their PhD. I remember having to sit them down and say, look, this is not for you.

And I just don't think it's gonna work out. And I felt terrible and I liked them. You know, we got on, but they just, they just weren't gonna hack it. But do you know what they said to [00:22:00] me? Thank you so much because I know I'm not gonna do it. This is not what I want to do, and now I can go on and do the thing.

I will be better at. And so I think it was one of the most difficult things I had to do, and I've had another situation like that. But actually I, I do think you need to confront it because if it means then you liberate that person to do something that they're really good at, and of course. Again, we, how many times have we said this one size does not fit all and not everybody's up to doing a PhD.

They will be brilliant at something else and that's what they need to go off and find. 

Juliet Fallowfield: Amazing. And is there a question you'd like to ask for the next guest who would've also been a founder at some point? 

Russel Foster: Yes. I suppose if you have a partner and a family, how do you balance the demands of a new business and.

The immense emotional input that you have to put into that with maintaining the relationship and your contact with [00:23:00] your, with potentially your children. Yeah, and I, I, I've been in that space and I know that it's really tricky and I would be fascinated to, to hear how. Other people deal with that. 

Juliet Fallowfield: Every guest that we've interviewed so far this season has said, yes, mobility is important, but sleep is more important.

And yes, nutrition is important, but sleep is the most important. So thank you. I mean, this will be very, very welcomed by many people. Thank you for your time. Great to chat. 

Russel Foster: Oh, delighted to chat. It's so great fun. Thank you. 

Juliet Fallowfield: