Oct. 20, 2022

"Sleep and the Athlete" with Professor Neil Walsh

Episode 178 of the Institute of Performance Nutrition's "We Do Science" podcast! In this episode, I (Laurent Bannock) discuss "Sleep and the Athlete" with Professor Neil Walsh (Liverpool John Moores University, UK).

Discussion Topics Include:

  • What is sleep, and why do we need it
  • Methods to assess sleep quantity & quality: from the sleep lab to wearables
  • Sleep and athlete health & performance
  • Strategies to improve sleep (from "sleep hygiene" to nutrition)
  • The "sleep toolbox" for practitioners

Podcast Episode Transcript: Download PDF Copy

Key Paper(s) Discussed / Referred to:

Related Podcast Episodes:

Check out our other podcasts, publications, events, and professional education programs for current and aspiring sports nutritionists at www.TheIOPN.com and follow our social media outputs via @TheIOPN






[00:00:00] LB: Welcome to episode 178 of The Institute of Performance Nutrition's We Do Science podcasts, the IOPN podcast. I'm Laurent Bannock. And today, I had a discussion a really fascinating discussion, with Professor Neil Walsh about sleep and the athlete. 


Now, yeah, I've gotten into this topic before with Dr. Shona Halson, for example. Another expert on this topic, who's actually co-authored one of the papers that we talked about today with Professor Neil Walsh, because it's just that interesting. And there's been some new developments in this area which we get into in today's conversation. And just generally cover the topic again in a number of different ways, which I think you'll find of enormous value. 


I mean, face it. We all have an idea about whether we've slept well or not. And there is no doubting the importance of sleep at least on how we feel and certainly for our athletes. We want to help them perform and function at their very best. And sleep really has a broad range of impacts, whether it's cognitive functions, performance, health, recovery. And indeed, to us, as nutritionists, the decisions, the influences that it may impact in terms of reaching for things like coffee, caffeine, of course, and foods that might make us feel better if we're feeling a bit rotten from a lack of sleep. 


But it is an incredibly important area. And as the body of knowledge in this area continues to involve, I, for one, am particularly interested in talking to the experts about what we should know about this. 


Anyway, you're about to hear about sleep and the athlete in just a few seconds. But before I do, please do check out the page for this podcast. I'm trying to develop this section on the website further. Bear with me. But there will be a lot more resources in the coming weeks and months on our website. But you can, for now, at least access the papers that we refer to all under podcast at www.theiopn.com. And just click on podcast there, of course. 


Whilst you're there, check out our educational outputs, particularly our flagship program our Advanced Professional Diploma in Sports Nutrition. The latest version of that program is about to launch this November 2022. It's just an enormous evolution in everything that we've done. We're incredibly excited about it. It is entirely unique in as far as it is entirely focused on developing your skills and knowledge in the area of applying the science of sport and exercise nutrition into practice. It's heavily focused on practice. Helping you do your very best with your clients, with your athletes, with your teams in terms of the strategies and the coaching skills that goes with it. There's nothing else like it. So, go check it out at www.theiopn.com.


Whilst you're there, check out our so software, which is also there to support you as practitioners working either with private clients, group coaching online, team settings in any area of sport and excise nutrition, from active members of general public, to elite professional; football players, rugby players, Olympians and so on. This is what I use it for to great impact. I know that you will find it of great value. You can learn about that at www.theiopn.com. And also, our various other offerings that we have. And as I said, some massive news that will be coming very soon about our institute and also the various things that we offer. You can check that out at www.theiopn.com. 


Anyway, for now, please enjoy this conversation that I had with Professor Neil Walsh about sleep and the athlete. Enjoy. 




[00:03:51] LB: Hi, and welcome to The Institute of Performance Nutrition's We Do Science podcast. Today, I have Professor Neil Walsh with me today. Now, do not adjust your headsets or your sound, because Neil is possibly the bravest guest that I have had on today because he is suffering, shall we say, from something we've all heard of in the past few years. But he is being a proper soldier about this, and he's going to come and have this chat with me about sleep and the athlete and how that affects health and so on. And it might be a rather apt conversation to discuss his own sleep habits and how that might have influenced his own current condition. 


Anyway, Neil, welcome back. And of course, I say welcome back, because you're not new to the podcast. We've talked about athlete health and immunity in the past. And you've done some lectures for us quite a few years ago now. We've just been discussing how old we both are. But anyway, welcome back, Neil. And thank you for doing this even though you're not feeling too hot right now. 


[00:04:55] NW: Thank you, Laurent. I thought it was man flu. But I think I've recently found out it's COVID. So, apologize for the audio and the odd sneeze. 


[00:05:04] LB: Look, I really appreciate you being on today. I know there may be a little bit of coughing and whatnot. But I think we'll still manage to have a productive chat for everyone. Now, we have discussed this concept of sleep before. And I've had Shona Halson on before, a few years ago now, to talk specifically about sleep and the athlete. But the body of knowledge on that has evolved somewhat since those conversations. But also, very recently, you published another study beyond the BJSM review, narrative review, on sleep and the athlete, which is part of what we're going to talk about. But specifically, you've got another study that came out on perceived sleep, or good perceived sleep quality and how that may impact upper respiratory tract infections is a particularly interesting area for reasons we'll get into. 


But Neil, tell us a little bit more about yourself. Not everyone has listened to those prior podcasts or may not yet know who you are. Just give us a quick intro as to who you are what you're currently up to. 


[00:06:13] NW: Of course, Laurent. Yes, I'm Professor Neil Walsh. I'm a professor of applied physiology at Liverpool John Moores. I joined Liverpool John Moors University in 2019. And before that, I spent nearly 20 years at Bangor University, where I sort of led the extremes research group with a lot of interest in the health and performance of athletes, but also military personnel. We sort of look at all of those factors that sort of impact health and performance in military recruits. That could be nutrition. It could be stress and anxiety. And obviously, sleep is one of our really key focuses right now. 


[00:06:50] LB: Yeah. And some people are going to be listening to this going, "How? I thought this podcast is about nutrition." Well, we talk about various topics on exercise physiology, sports science, health and so on that's relevant to athlete health and performance. But also, sleep is a particularly interesting area because it is an area that does engage the nutritionist or the performance nutritionist quite a bit. I certainly find myself dealing with sleep education and athletes, and/or trying to impact sleep, because that can have some interesting links to nutrition, for example, as per previous podcasts on this topic where we've been looking at how sleep quality might affect satiety, hunger, sort of the choices that people make in terms of food, and beverages, and stimulants, and various other things, which we'll get into. 


But this concept of sleep and athlete health performance is a very broad one, obviously. Hence, not just your era of research in athletes, and tactical athletes, military personnel and so on. But it's something I think we're all interested in as adults, particularly parents in my case. I've had years of sleep disturbance. Thanks to my lovely children. And one way or the other, it's something I – you can't really ignore this concept of sleep. 


The idea that we can impact it for a better quality of life and, of course, potential improvements in performance and/or reducing the negative consequences that may be linked to it is of interest to so many people. But I'm interested. The listeners are interested. But why did you get into this topic as deep as you did, Neil? 


[00:08:40] NW: Well, I started out in my career I guess as an exercise scientist, an exercise physiologist. And after many years of sort of assessing the impact of exercise during training on, for example, the immune system, infections and immune function in athletes and soldiers, I started to realize that exercise is only one small part. 


Stresses, like exercise stress, influence the immune system, our health generally, by activating the stress axis, the hypothalamic pituitary adrenal axis. And exercise is only but one stressor. The athlete or the soldier has to deal with psychological stress. They have to deal with disruption to sleep, whether it's traveling to a major competition and jet lag or its deprivation of sleep. They might be suffering poor sleep. They also have times when their nutrition might not be adequate. And exposure to extreme environments. 


We now take in my team a more holistic approach. We understand the sort of pressures on the athlete's health are multifactorial. We can't just look through the lens of nutrition, for example, Laurent. It sort of opened our minds.


[00:09:54] LB: Yeah. I mean, you've taken me right back to our earlier conversation a few years ago about that holistic viewpoint that you use when we look at the health of an athlete, rather than very specific reductionist, if you like, perspectives on what impacts immunity in athletes, of course, and what we're interested in. 


But that bigger – the sort of the combined thing that we exist through 24 hours doing lots of different things as human beings, as athletes and so on. And there's personal issues. There are professional issues. There's stuff happens, right? And of course, that combined load is all very interesting. And of course, yep, that's going to impact sleep, or sleep will impact that as part of that. And I like that perspective that you've taken. I definitely want the listeners to listen to that podcast if we haven't already done so and that paper that you've done that links to that. 


But we're talking about sleep specifically. And I think what would be helpful here is if you can actually define that word sleep and then contextualize that into why it's important for human beings. Anyway, why do we even need to sleep?


[00:11:10] NW: Yeah, that's an important one. And it was the founding father, if you like, of modern sleep medicine, Allan Rechtschaffen, way back 50 odd years ago. Who said that sleep doesn't serve an absolutely vital function, then it was the biggest mistake that evolution has ever made? 


And you have famous people who – Thomas Edison was a very famous inventor, who reckoned that sleep was something that should have been left in the dark ages in the caves. And he slept for about three to four hours a night. And we know of all these other famous people, politicians, pop stars and so on who apparently survived on very little sleep. What do we know about sleep and why is it important? 


Well, the offline conditions in sleep we know are important for cognitive function, memory development, learning, and not least with a physical function that we're so interested in. Studies have shown in animals and in humans that only a small amount of sleep disruption or deprivation over a day or two. Sleep, complete sleep loss, for example, over a day or two really reduces memory, cognition, attention. And then of course, we know that studies now show that endurance, performance, etc. is also lowered by uh sleep deprivation. 


The effects of more prolonged sort of more subtle disruption are not particularly clear on exercise performance. It's very rare that an athlete would miss a whole night's sleep, for example, like a soldier would. And we know that disrupts performance. 


We know that sleep is very important for health and performance. And you have these sleep is broken up into four stages throughout the night that cycle every 90 minutes or so. The first three stages are non-rapid eye movement sleep. The first two of those three stages are quite light sleep. And stage three is more deep sleep.


We know that stage three or deep sleep is very, very important for the immune system. And that when you ask somebody about how they rate their quality of sleep, that seems to relate quite well to stage three sleep measured using polysomnography. 


And then finally, stage four sleep, or REM sleep, which is rapid eye movement sleep where your eyes are moving behind your eyelids. Your body tends to be paralyzed in that sleep phase. And this is when most of our dreaming occurs. And that's a good thing. Because obviously you don't want to act out your dreams. Being paralyzed during REM sleep is actually quite a good thing. But it's that stage of sleep. There seems to be well related to sort of dreaming, memory development and cognition and emotion. Each of those stages are important. We also know, Laurent, as I'm sure we'll get into, that athletes do suffer poor sleep.


[00:14:02] LB: Yeah. And that phrase, poor sleep, in itself is interesting. Because we talked about defining sleep and what it is, which of course we have – you're able to talk about that for a period of time or write about that for a period of time. But where are we actually in that definition of sleep and conceptualizing what we do and don't know about what sleep is? And why or is it not important? 


I mean, you, for example, used a phrase there. Famous inventors and rock stars make comments about how they've survived for a period of time. But perhaps, if they more than survived and thrived, perhaps they would have done even greater things. What are your thoughts on that? 


[00:14:47] NW: Well, and also, I mean, I won't get into this. This is not my area of expertise. But there's now an interest in long-term sleep problems. And of course, dementia, for example. We also know that people who have chronic sleep debts, so these are short sleepers over the long-term, there's a greater incidence of inflammatory diseases in those individuals with chronic short sleep. Here we're talking about inflammation. So, you see increases in those populations with IL-6 and CRP inflammatory, cytokines and the like. They have increased incidence of type 2 diabetes, heart disease. Obviously, obesity is more common. We know that there is a long-term impact to mental health but also physical health of chronically sleeping short, Laurent. 


[00:15:38] LB: I guess what's interesting – and there's going to be a few rabbit holes, I think, we'll slip down here. We're not just talking about human beings existing in the real world, civilian life, or general population stuff. We are talking about high-performing individuals. 


And I've talked about this before, that the reason why I prefer the term performance nutrition, for example, is because that enables us to encompass the broader range of high-performing individuals, whether it's, yes, athletes, which in itself requires definitions, of course. Particularly when we use word words like elite. But there are people like tactical athletes, not just soldiers, or special forces operatives, but also police, to fire services. Some of those people can be very high-performing. I'm thinking of individuals. With all the effects of climate change, we see all these fires, for example. And there are people engaged in unbelievable high-performing requirements, physically, mentally demanding, where there are going to be impacts to their sleep. We're not just talking about will this, won't this affect. Somebody's ability to write something, be creative or win a gold medal. It can be life and death. It's pretty critical. And that, I guess, goes back to your comment about it could be the biggest mistake that evolution ever made. And intuitively, we all do feel the importance of sleep. 


But in the context of high-performing individuals. And we'll bag them into the term athlete, whether it's tactical, or professional, Olympic, whatever. Why, though, is sleep something that we should be spending at least the bare minimum of time to try and correct or improve?


[00:17:24] NW: Well, we spend about a third of our life sleeping, first off. And we know, and we talked about this in the consensus review in British Journal Sports Medicine 2021, that I was very lucky enough to lead a category of amazing experts on this topic. 


We know that sleep is really important for athlete health and performance. There's good evidence that disrupted sleep over the long-term has negative impacts on athlete performance and also how the athlete feels when they wake up in the morning. Their mood. How refreshed do they feel in the morning? 


We know from mainstream science that sleep loss impacts on the immune system via activating the endocrine axis that we've talked about numerous times before. I think we know that sleep is important for general health. We know it's important for the health of the athlete. And therefore, performance. 


I think we need to do what we can to optimize sleep in our athletes to avoid performance deficits. For example, when you increase training load, Laurent, in athletes. Good training studies, overreaching type studies, where there's an increase in load, we do see an impact, a negative impact on sleep. You see changes in sleep duration and sleep efficiency, the percentage of time spent in better sleep. And this seems to relate well with poor performance during overreaching, for example. 


Now, it's a chicken and egg situation. We don't know, of course, from these studies whether when an athlete increases their training load and they suffer poor sleep, which is it kind of which causes which? The mood disturbance you see, is that because of poor sleep? Or is it the heavy training alters mood and stress and that all to sleep? Or is it something to do with the immune system that's lowered during very heavy training and stress? And that then increases your chance of getting ill. And we know that illness upsets sleep. We don't really know fully about that interplay of those different things. But we're very clear now that sleep is very, very important for athlete performance and health.


[00:19:32] LB: I cast my mind back to various conversations with you and Shona, in particular, about these sorts of topics. And it is incredibly interesting about what the evidence appears to be telling us. And of course, there's differences in the evidence, quality, relevance of that evidence, which we can dip into in a second. But you know it is something that one way or the other we seem to have an idea whether it's just a reflection of, "Ah! I didn't sleep well last night." Or, "I did sleep well." For whatever the cause is, we still have a feeling whether or not we had a good night's sleep. And that in itself's interesting. And we'll talk about your new research in a minute about the potential difference between the perception or not perceiving it, because I find that particularly interesting. 


But we do live in a gadget-driven, gadget-infested world, which I'm definitely a techie sort of guy. I love gadgets. And I've experimented with various devices to assess activity, and stress levels, and sleep quality and so on. But as per many of the conversations that I've had with experts doing the highest level of research in these areas, there seems to be a pretty big gap between the quality and relevance of the information that's delivered by some of these tools that we have widely available, whether they're validated or commercially available is, again, another topic. 


But one way or the other, sleep is something that we can sort of put our finger on it. But that in itself, of course, is a big issue. Isn't it, Neil? Because how do we even assess this? Maybe you could tell us what happens at the highest level. And then how does that trickle down to what we think we can measure and the reality of what we're actually measuring or not measuring? 


[00:21:26] NW: In the sleep laboratory, of course, you can use sophisticated polysomnography. And that will allow you, and the very controlled conditions, to assess those sleep stages that we talked about earlier on. Those four sleep stages, non-rem and REM sleep. 


The challenge, of course, for us working with athletes and military personnel in the field is, well, how do you take the lab to the field? How do you have objective useful measures of sleep? Whether that'd be the quantity of sleep or the quality in the field.


And again, in our consensus review, Shona wrote a really nice section on the measurement tools. The most validated and practical, of course, is the ActoGraph, which is a small wrist worn like a watch that measures the movement. And that has been validated well against polysomnography, the gold standard. 


But of course, as you know, there are now a myriad of commercially available devices that you can wear on your wrist. You have the [inaudible 00:22:31], the phone apps. Your phone sits by your pillow. You have the ring. You have so many different devices that are available. And not all of those devices, as you've alluded to, are validated. The ActoGraph is the one that's mostly used in larger population studies because it's validated. 


Then the other issue as well is that we can't access a scientist, the algorithms that are used to produce the sleep data from these devices. There's a lot out there in terms of available devices is an apps that you can use. How do you use them and how do you interpret them? 


I mean, one of the worries that we've talked about regularly is that athletes become obsessed and really worried about looking at their sleep data. And you can't unsee your sleep data in the morning. And you see that your sleep duration was far shorter than norm of the morning of a competition. We can see the problems with that quite easily. And your sleep quality was poor. What do you do about it? 


I think that's something for a sports scientist really to consider carefully in terms of education about sleep and about the use of those devices. But certainly, if you want to get valuable information as a researcher, the ActoGraph is useful in a field setting because it compares well with the gold standard. But the validity of the other devices has not always been tested, Laurent, unfortunately. 


[00:23:53] LB: Yeah, that I find interesting as a practitioner myself. It's an area that we regularly explore on this podcast. These discussions come up all the time about we can measure, but should we measure? What are the strengths and limitations of these devices? 


I mean, I think back to a podcast I did with Dr. Julia bone, and we talked about DXA. Is it really gold standard? Or as she proposes, possibly gold-plated. But at the end of the day, a lot of this will boil down to our understanding of the strengths and limitations. And actually, a lot of these things all have value. It's just a question of how you choose to use it and interpret it. And like you said, there could be some problems there.


But I know for myself personally using these gadgets, I've been absolutely fine when I wake up. And then my phone tells me that I didn't get enough sleep. And that then takes me into a conversation I want to have with you now about the relevance and role of the perception of sleep. Because we all do. We all wake up. Talked about it earlier. And we've all had an idea, "Oh, I didn't sleep very well." I ask my kids every morning, "Did you sleep all right?" It's always interesting to hear their responses. But of course, we then get the impact of these devices. The perception versus the actual amount of sleep. What did you guys find about that?


[00:25:18] NW: Well, I think the first thing to say is that there are good laboratory studies and sleep labs that show when you ask somebody how good was their sleep last night on, say, a one to four scale, from one, very poor, to four, very good, that actually individuals are very good at actually rating the quality of their sleep compared with objective polysomnography measures. 


For example, when you ask somebody about their quality of their sleep, they often relate that to how quickly they got to sleep. They'll tell you it was a really good sleep if they had a short sleep latency. How long it takes to get to sleep? And also, when you ask somebody about the quality of last night's sleep, not only do they think about, "Well, how quickly did I get to sleep?" But they also think, "Well, how disturbed or not was my sleep? How continuous was my sleep?"


And there were good studies actually from [inaudible 00:26:15] group, some of the work that was done originally at Liverpool John Moore's as well, that shows that people are very good at rating the quality of their sleep. And that relates tightly to the polysomnography, the objective measures. 


And what happens with our recent work is we and others have published studies showing that in soldiers, and Sheldon Cohen had published work in the general population, that individuals who short sleep, so, individuals who sleep less than the recommended seven hours, they are more likely to get respiratory infections. 


Sheldon did a very famous study where he quarantined individuals. He placed the common cold. He placed that up the nostril, one of five common cold viruses, and he quantified their sleep in the two weeks before. And sure enough, individuals who had had short sleep were much more likely to then develop the cold in the quarantine, the hospital environment. 


We did the same in a large military population. We showed that military recruits during training who slept less than six hours consistently were four times more likely to report to the dock with a respiratory infection. 


And many years went by after these studies, and then I fell upon a study on pneumonia risk in nurses. It was part of the nurse's health study, where they had nearly 60,000 female nurses. And what they did was they looked at pneumonia risk and the length of sleep in these women. And what they showed, the main message of their study, was that if you have five hours sleep or less a night, you are much more likely to have pneumonia. And this was not surprising, because it fits with the work on other respiratory illnesses like the common cold, like Sheldon Cohen had done, like we had done with the military recruits. 


But when you look a bit more closely in their results section, there's a really fascinating finding, which didn't make a big headline in their paper, which was they'd also asked the women nurses, "Do you feel that your sleep duration is adequate?" They'd ask them a question that was more individualistic, if you like, "Was your sleep adequate?" 


And in those individuals who said their sleep was inadequate, again, those individuals who slept less than five hours were more likely to get pneumonia. But the real bombshell for me that I couldn't stop thinking about for a couple years, and it led to our recent research, was that, actually, the nurses who slept less than five hours who thought their sleep was adequate, they had no greater risk of pneumonia than those individuals who were getting seven or eight hours, as is the recommended for adults. 


There seem to be some protection provided against respiratory illness in those individuals who did really short sleep. This is five hours or less sleep. But that had somehow thought their sleep was adequate. They'd got enough sleep. This raises the specter that, actually, we need to be pushing less than just the duration recommendation, but considering the individual sleep needs. It's probably not appropriate to just consider that we all need seven to nine hours sleep. We've all got individual sleep needs. 


This, Laurent, sent us on a path. What happened was we'd had that large population of military recruits. And we'd originally looked at the duration they slept and their risk of illness. And we'd shown that short sleepers get more sick. But what we also did in that study was we'd asked them at the start of their training, "What was the quality of your sleep last night on a one to four scale?" Which is a very standard question used. It's actually in the standard Pittsburgh Sleep Questionnaire. It's used in hundreds and hundreds of studies. What was your sleep like last night? Was it from very poor? That's a one. To four, very good. 


We've gone back to our data and taken a fresh look. What we also did in that paper that's just been published in the journal sleep is, again, we individualized, because we're now starting to take an approach thinking about the individual. We individualized the level of sleep restriction that the recruit was experiencing at the start of military training relative to the sleep that they normally got during civilian life. They turned up at training. We asked them about what times you normally go to bed. What time do you normally wake up in your previous life? 


And then in the first week of training, we found out about their sleep last night. So, early training. They're not sleeping – they're getting up quite early. And we ask them about their quality. And we did that again at the 12th and final week of training. What time do you go to bed last night? What time did you wake up this morning? And we asked them about quality.


By going back to the data, what we were then enabling was we could look at the level of sleep restriction that they were experiencing versus their civilian life. And studies in this space have actually used two hours as a kind of key cut-off, where beyond two hours, this is sleep restriction. Anything less than two hours is not really sleep restriction. 


And studies have shown impacts on inflammation using that cut-off of two hours, heart disease risk and so on. And also, between the working week and the weekend, it tends to be about an hour and a half to two hours more sleep that most of us get at the weekend compared with getting up early for the busy work day. 


And so, there were two real main findings, Laurent, in this new study. The first one isn't that surprising. It's that those military recruits who had sleep restriction, so, more than two hours sleep loss compared with their previous civilian life, they were three times more likely to suffer respiratory illnesses than those who had less than two hours of restriction. 


But that was only a small part of our finding. The really exciting finding, which aligns quite well with that study of pneumonia, was that when we delved a little bit deeper and we looked at the sleep restriction group, what we saw was startling. What we saw was that the quality of the sleep mediated the effect of sleep restriction on illness. 


In simpler terms, what we saw was that the effects of sleep restriction on illness were driven by those people who reported poor sleep quality. If you had good sleep quality last night, but you were suffering sleep restriction, you were at no greater risk of suffering respiratory illness, the individuals who had no sleep restriction at all. 


It seems that we can't just look at duration and how much restriction somebody's suffering compared with their preference for how long they sleep. You have to consider the quality of sleep as well. I know that was a bit lengthy, but I hope that makes sense, Laurent.


[00:33:21] LB: No. It's fascinating, Neil. Because that perfectly brings me into a conversation I want to have about this area that you've already introduced about, quantity versus quality. But also, if we bring this to what I consider to be particularly relevant, and that is that, as a practitioner, I'm working with individuals. Even if I'm working with a team, it's a team of individuals. And clearly, there are differences between those individuals. And we're not even talking yet about the imposed demands of sport and travel. And if we go down the military pathway, there are beyond basic training, actual serving soldiers and operatives that have a very chaotic situation that they're in. And not only is it unpredictable. It's pretty – Well, yeah. We don't even have to go there. 


However, we're trying to understand not at this point just how important sleep is. But what can we actually do about it? And I guess the measuring it, the understanding the quality and the quantity and so on is what gets really interesting. Tell us a bit more about that. And also, how individuals will vary as well? 


[00:34:37] NW: Yeah. And there's some really nice information on a Charlie Sergeant's papers in IGSPP with athletes. That almost highlights even more the relevance of this. You talked about individual differences between athletes. And what they did in their work with 175 athletes, small proportion were female, they were elite athletes. What they've done is they've shown that athletes do suffer sleep restriction. 


And again, this is not a surprise. But what they show is that the athletes are restricting their sleep to make way, for example, for their training in exactly the same way as we're doing when we get up early for the morning commute, or we get up early in the working week just to start work early and get ahead of the game. And in the same way that our military recruits, they got up early in the morning to start training.


What they showed sergeant and colleagues is that they asked the athletes, "What is your sleep need? How much sleep do you think you need to feel refreshed?" And most of the athletes said, "Just over eight hours. I need about eight and a bit hours to feel refreshed and okay." 


But then they measured what they actually got using an ActoGraph, the wrist-based device we talked about, and most of these athletes were not getting the eight and a bit hours that they wanted. They were getting under seven hours. The values were 8.3 hours and 6.7. You've got an over an hour and a half of sleep deficit, which is the difference between the measured sleep using the objective device on the wrist and the amount of sleep that the athlete thought they needed. And there was a deviation of over an hour amongst those athletes. 


I looked very carefully at their data, and was just as startled. Not just the, "Oh, golly! They're getting an hour and a half or more less than they need." But actually, there was a huge tale, as you allude to. There was a big variation in the spread. And then it depended also the deficit on the sport. And this won't come as a surprise to you. But sports-like swimming had the largest deficits. The swimming group actually was two hours, which is the same as our two-hour cut-off that we used in our military study and that general sleep scientists have used in their studies of cardiovascular disease risk and sleep restriction. 


The swimmers had a two-hour deficit of the actual sleep they were getting compared with what they thought they needed. The triathletes were the same. And a good proportion of that deficit won't surprise you. It's just like the military setting. It's because they're getting up so much early, earlier in the morning. Because for triathletes and swimmers, the swim early in the morning is just ingrained in their culture. And they were getting up – They were going to bed at 11 PM or just after and getting up at around 6 a.m. Whereas they probably needed to be getting up at seven half, seven or even eight o'clock in the morning. But they just have to get up early to fit their training in, to fit their life in. 


Sleep restriction is clearly something that most of us are doing, whether we're elite athletes, getting up early for the commute, or a military recruit. And this is having an impact on health, and more than likely their performance. And I also think this is a problem for the studies of performance in sleep, because there's been some really exciting work recently on banking sleep. Can you bank extra sleep or extend your sleep? And can this improve performance? 


And there's been some quite positive findings on that. In endurance athletes where, for example, they extend their sleep over two or three days and then they see that the sleep extension actually improves endurance performance. But when you interpret that in this new context of sleep restriction. It's really hard to know whether the improvements in performance with sleep extension are true effects of banking extra sleep or they're just restorative recovery sleep. Because even in those studies of sleep banking, what you see, Laurent, is that the athletes are sleeping less than seven hours before they actually extended their sleep. Because just like these swimmers were talking about here in other athletes, most athletes are already restricting their sleep. We don't know if sleep banking is improving performance because it's recovery sleep, because they've been sleeping short. Or it's a true effect, Laurent? 


[00:39:15] LB: Yeah, that's really interesting. And again, just from a sort of casual observation of what happens in the real world, real life, there are situations like with your many athletes will have a schedule that they have a program of events and so on, where, I guess, to a certain extent they can they can strategically sleep around that schedule. Whereas, for example, with active serving soldiers in combat situations, for example, will have considerable amounts of sleep disturbance, sleep restriction, or whatever for obvious reasons. 


And so, it goes in normal people's lives. Not to say that soldiers aren't normal people. But in regular people. It could be a car honking its horn late at night. Or your children waking you up. There's going to be a tolerable amount of this disturbances that the body can handle without it impacting performance. And of course, we go back to the concept of the individual. And some people are also – You talked about chronotypes. Morning people, evening people, and larks and so on. 


I mean, in sort of mixing all of that together, what are the issues that that raises for you particularly from a researcher's perspective? Because you're generalizing a lot of things. Not you specifically. But that's how one approaches the research of this. And how do we therefore tease out what we're supposed to know about this as a consequence of that? 


[00:40:54] NW: The problem here is the over-reliance on a one-size-fits all, whether it's sleep recommendations for an adult to get seven to nine hours, for example. Or the way in which we've approach our research studies. We often adopt the one-size-fits all. And what we've learned, or certainly I've learned in my research career, is that many of these things are individual. And the sleep need is certainly individual. And the degree of sleep restriction in those elite athletes I mentioned a minute ago, there was a massive spread on the amount of sleep restriction between the sleep they were getting, the duration they were getting, and what they felt they needed. 


I think we need to better account for the individual and their needs. We also need to account for the quality, or in this case, in our case, the perceived quality. And that relates quite well to the objective measures of quality. For sure, there are lots of other problems with the research, too, Laurent, that they're are too few female participants in the studies. The measures we've talked about not necessarily objective measures always. And then the other limitations in terms of the methods and statistics in terms of. It was only by going back to our data on sleep duration infection that we unraveled this important finding. You have to delve deeper and go beyond the face value. And then there's that aha moment, and the light bulb goes off, and you say, "Oh, my word! We did measure quality. I wonder if that had an effect." And we're often a bit one-dimensional, Laurent, I think.


[00:42:32] LB: Yeah. Well, I mean, it seems that way, doesn't it? And I think you've made it clear that sleep quality is a pretty major part of this. But that will of course vary from people to people based on their circumstances, which I always find it interesting how technical the concept of sleep architecture is. You can spend a lot of time reading about how complex sleep is and the various phases of sleep. But it would be worth just quickly delving into that in terms of what's relevant about that as it relates to the circumstances that athletes will find themselves in. 


[00:43:10] NW: Yeah. I think the first thing to say is that we are not just pushing quality. Because in our findings, actually, there was no effect of good quality in those individuals who – there was no beneficial effect of good quality in those individuals who had no sleep restriction. It was an interaction, which we showed, whereby when your sleep restricted, quality matters. And in that setting of sleep restriction, what we saw was that good perceives the equality and sleep restriction was protective. But that the effects on infection of sleep restriction were driven by those people who had poor quality. 


It's certainly not that quality is just more important than duration. There's an interaction between – there's an interplay between the duration. Or in our case, the amount of sleep restriction and the quality. I think both are really, really important. 


But remember, we individualized the sleep restriction based upon the individual's civilian sleep before they started training. It's also important to individualize this. We're definitely not saying don't measure sleep duration. Don't measure architecture. Although, of course, in the field, it's going to be very, very difficult to measure the architecture. You would normally want to do that in a sleep lab. That's very, very difficult to do in the field. And the commercially available portable PhD systems are not necessarily gone standard, if you like. 


It's duration and quality that matters. But to this point, Laurent, I think it's really fair to say, even amongst sleep scientists, that they have had an over-reliance and an over-obsession with duration rather than quality. 


[00:44:54] LB: Yeah. I'm really pleased you went back over that, because that's a big relief to most of us, I think, where we feel there are aspects of this we can't control, i.e., the Lorry beeping in the night, or our kids waking us up, or bullets flowing over your head. But there are opportunities that may present themselves. Or we can schedule in or plan in and/or program around it. And I'm thinking not just what we as individuals or as practitioners helping our athletes, our clients. But also, people that are designing training schedules, travel schedules and so on all need to get involved where an aspect of their consideration should be the impact on sleep. 


What would those considerations be? And I guess the main thing people are going to be wanting to get into here is what sort of the strategies can we employ to optimize this whole situation? 


[00:45:52] NW: Yeah. And the really good news here is that our science here can be implemented, because the next question somebody would ask, or they would say, "Well, if I'm restricting my sleep," and we know that poor quality sleep increases illness risk, "then how can I get good quality sleep even if it's short sleep?" 


And there are some really simple tips that athlete should follow. We did talk about some of those in our BJSM consensus. But there are five, really. The things that we all should make sure we do. The first tip is to adopt a consistent sleep schedule wherever possible. And that includes at the weekends. That means having a consistent bedtime and wake time in the weekdays and at the weekends wherever you can. 


The second one is to avoid large meals, to avoid high doses of caffeine and alcohol close to bedtime, because that can impact sort of sleep latency and the quality of the sleep. The third one is to, again, it sounds a bit obvious, but to make sure the bed and the pillow are really comfortable and the room is cool, dark and quiet. 


And whenever I speak to athlete groups, one of the complaints is the travel for the athletes and the comfort of the beds and pillows. I don't know. We can't always take our bed and pillow with us. But the comfort's really, really important as obvious at it sounds. 


The fourth one is to establish a relaxing bedtime routine. As you alluded to, go screen-free from about 30 minutes or so before bed. And just get into bed when you feel sleepy. And the final one is a very generic recommendation, which is that we know that taking on some exercise during the day shortens and sleep latency. It speeds up the time it takes to get to sleep. But of course, our athletes are going to be exercising anyway. And so, those are simple sleep recommendations that we would recommend the athletes follow to optimize their hygiene. 


There are other things that we talked about in the consensus review that the regular use of sleep education, that seems to be beneficial. Good studies show that if you have simple sleep education for your athletes, this can improve sleep duration and quality. But you do have to do that quite regularly, because the improvements in sleep duration and quality seem to wane quite quickly. That's what those studies show. You need to screen athletes to identify if there are more serious sleep problems. 


And of course, we talked a little bit about this, but we would encourage the afternoon nap in the athletes, and to consider this sleep banking or sleep extension before an important competition. 


[00:48:36] LB: Yeah, I love that. And actually, in the BJSM paper, you've summarize that as part of your sleep toolbox for practitioners, which is one of my favorite ways of looking at what we have available as sports nutrition practitioners in terms of things like education, and tools, and gadgets, and supplements, and so on are all part of our practitioner's toolbox. And that brings us back not just to having a nice packed stuffed – a toolbox full of all of these tools and strategies, but it is understanding what the strengths and limitations of those tools actually are. 


But given a major emphasis of mine, and the podcast, and our listeners is very much on nutrition. I just wanted to end this conversation specifically about nutrition and the impact that that can have on sleep quality and/or quantity. And just grab your expertise on this topic. What are your thoughts on that in terms of what the evidence tells us? And practically speaking, what can we as performance nutritionists actually do with these tools in our toolbox? 


[00:49:52] NW: Yeah, there are many available supplements out there on the market that purport to improve sleep quality and increase sleep duration. But there's limited well-controlled research to support those claims. 


I think the one we know most about is of course caffeine. And we did talk about that in the consensus. And of course, we know that caffeine is stimulant. We need to be very careful about the dosings of caffeine particularly near to bedtime. We need to avoid as I said in my tips. We need to avoid caffeinated beverages, etc., tea coffee and the like in the evening when we want to get to sleep. That's the one we know most about. And we know that some athletes are taking caffeine to try and improve their performance. There's a rub there. It might improve your performance, but it may well increase the time it takes you to fall asleep after your performance at night. And it might disturb the quality. I think caffeine's the one we know most about in terms of sleep latency.


The other supplements that's supposedly alter serotonin in your sleepiness level. We're not clear that the studies are not particularly well-designed with rigorous controls to allow us to determine whether those supplements do improve sleep quantity and quality. 


[00:51:14] LB: What about something that – we've certainly got into this a lot on the podcast lately. And it's a big thing in sports nutrition now, particularly in elite female athletes, aesthetic athletes and so on, is relative energy deficiency. Energy availability is something that we're trying to stay on top of us performance nutritionists. Is there a link there to sleep? 


[00:51:37] NW: I would imagine that mostly the link is that we know that sleep seems to be more of a problem for female athletes. There was some good work with a French International athlete showing that psychopathology was more prevalent in female athletes than male elite athletes.


And of course, problems with anxiety disorder, stress, depression we know relate to sleep and sleep disturbance. That might be a part of that connection, Laurent, in individuals who maybe have low energy availability.


[00:52:11] LB: Yeah. Well, maybe that's some future research, which I think could be of interest, right? And I know that, initially, particularly in the nutrition field, there were concerns about the impact of eating too late and whether or not that would result in adequate digestion, absorption and so on. And we subsequently have discovered for the most part that that isn't such a big problem. 


But the proximity of meals to sleep and maybe the types of food, I'm thinking heavy meals if we can be very general about that. Is there anything we should be concerned about or aware of? 


[00:52:50] NW: Yeah. Again, there's some good research that shows that if you eat a meal four hours before bed, compared with eating a meal an hour before bed, that unsurprisingly, eating the meal one hour before bed, it lengthens the time it takes you to get to sleep your sleep latency. We'd certainly recommend eating a few hours or more as best you can before bedtime. Avoid those large meals close to bedtime. Avoid the caffeine close to bedtime and alcohol as well, Laurent, yeah. 


[00:53:20] LB: No. That's brilliant. Well, I mean, I feel like I need a nap. I need to bank some sleep. My kids are out the house. So, I'm going to go bank some sleep, Neil. 


There's a lot there that we talked about. There's obviously stuff we didn't talk about, A, because we haven't got time. But also, the listeners can actually read those narrative reviews, consensus statements, which I'll link to in the show notes on the page for this particular podcast episode. 


But obviously, I also mentioned, we have had these conversations in the past with Dr. Shona Holson, who went into a great deal in things like sleep architecture and the impacts of travel, and jet lag, and where we are on the planet, and light and day and all that stuff, which is all worth listening to. 


But Neil, I just wanted to say thank you so much. I guess, the last thing I wanted to ask you is where do you feel the research needs to go in this area? What are the sort of things that you're working on? What needs to be done? 


[00:54:24] NW: I think it's exactly as I said before. Thank you, Laurent. I think it's that we need to consider the athlete's individual sleep needs. And simple measures like how refreshed they feel in the morning. That's where our focus is on trying to use behavioral interventions, for example, to improve sleep quality in the hope that that might you know reduce their susceptibility to infections. 


[00:54:45] LB: Thank you so much, Neil, for your time today. It's been another really enjoyable conversation. You did incredibly well despite having COVID. It does not go unnoticed. We really appreciate that. 


And like I say, I'll put links to everything. People can look up your work and your research. And I look forward to having you back on We Do Science at another point in the future when this topic evolves even further.


[00:55:13] NW: Thanks, Laurent.