Caffeine, sleep and wearables, oh my!
While everyone’s looking for the next best diet, pill, powder or supplement to give them everlasting life, sleep and recovery are often criminally overlooked.
That’s why this week I’m chatting to Dr Dean J Miller!
He doesn’t have any fancy supplements or diets to sell you, but he does have some tips that will dramatically improve your health, recovery and longevity so listen up.
Jono: Welcome back to the Bite Me Nutrition podcast. I am super excited about today's guest. I say that about every guest, but that's because I'm very lucky to talk to a bunch of incredibly smart people. And I've got another incredibly smart person here with me today. I've got Dr. Dean Miller. I've been following him for a while. I can't remember how I came across you, but it would have been something to do with, I think probably a wearable research and your comments on that because there's a lot of noise in that space. I really appreciated the stuff you were saying. It seemed to cut through all of that. And so we'll definitely be chatting about that. that. But before we do, who are you? What do you do and why do you do it?
Dean: Yeah, no worries. Thanks for having me on, firstly. Johnno, I think the first, I might've dropped into your DMs when I first started my Instagram page, I think, to get some advice on your content, because obviously we know how great
Dean: it is. Yeah, so I'm Dean Miller. I'm a sleep scientist, so I have a PhD, looking at sleep around athletic populations. At the minute, I'm working at Central Queensland University, but based out of Adelaide, South Australia, research on wearables, shift work, jet lag, that sort of area. And I also work with athletes and sporting bodies to to recommend sleep practices to athletes that are traveling or going to the Olympics or just day to day sleep management. So that's what I do with the minute. And then when I when I have time, I try to put out some some content out there. It is hard. So I'm very impressed with your work. But yeah, so hopefully we can cover some nice content today.
Jono: Yeah, awesome. Yeah, and we'll link to, you know, where to find you at the end for sure.
Dean: Thank you.
Jono: And I think recovery, sleep in the like, athletic populations, I work with some of those not to the extent that you do, but definitely have even just, you know, regular, regular gym goers. That sounds mean, doesn't it? You
Dean: Yeah, yeah.
Jono: know, what people who aren't making a living and then a lot of young families and then a lot of shift workers, those are kind of like the three main populations I see. And
Jono: I mean, I know sleep is three populations, it's where it's the most affected.
Jono: So I was really excited to ask you a bunch of questions about sleep today and see if we can find any 1% that people can apply at home to improve their sleep. But I'm going to start with a very selfish question that's relevant because due to a, I don't know if we want to call him a colleague, but another large profile on the interwebs delay coffee in the morning for I think it's two hours. I think that was the seemingly random window that came up. Do I need to wait two hours for my first damn coffee of the day, or can I just get up and have a coffee?
Dean: It is a bit of a loaded question. So basically I think the premise of those recommendations from I guess a few people actually put them out now based on a number of things is the cortisol awakening response in the morning. So cortisol is basically associated with stress but that happens every morning. It's not a bad thing. So in the morning is when cortisol rises and then it plateaus and then it goes further the day and there is a thought that caffeine first thing in the morning can interrupt this cortisol awakening response or raise above the baseline levels that you usually would have causing more stress. So that's basically the rationale behind that recommendation of not having you for coffee straight away.
Dean: The second point is that the way the coffee actually this molecule called adenosine or adenosine that people say in a few ways, that goes into your bloodstream and into your brain and basically that blocks the receptor site. Caffeine blocks the adenosine receptor site and adenosine makes you feel tired and that's why caffeine basically makes you feel better. It blocks the sleepy hormone and in the morning if you're while you sleep, it flushes out, and you should wake up with very low levels. So the very premise of that mechanism is that caffeine shouldn't have that much of an effect in that context.
Dean: And then what I'm saying is, if you wanna have a coffee in the morning, you're running around with your kids, you're having a sip of it, you probably drink it over the first two hours anyway, it's not gonna ruin your day. So if that's when you need to have your coffee to get through the morning and by all means do that. If you can wait a little bit, you probably might get more beneficial effects of the caffeine. But in saying that if you're going straight to the gym and you want to get the benefits of a caffeine dose into your bloodstream for performance, then go for it. So then if I'll answer your question, probably a theme today where I answer your questions in one or two different ways.
Jono: That's science, right?
Dean: Exactly. Yeah,
Dean: and then
Jono: yeah, it depends.
Dean: the other thing is also people, if people wanna try this, they can try it out. There's a thing called sleep inertia, which is a thing when you wake up, or if you have a nap in the afternoon and you sleep a little bit too long and you wake up and feel like you're in next week, and that's called sleep inertia. And that should last anywhere from 10 to 30 minutes. And that's not actually related to how tired you are, up and caffeine is not going to do much for you in terms of your sleep inertia. So if you think that morning coffee is going to fix that, it probably won't. So if you wake up and you just wait a little, if you wait that 30 minutes, if you usually have that coffee then you might feel good anyway and then you can have that coffee two hours later. So use yourself as the experiment, try a few things, but at the end of the day if that's prefer to perform or to get your kids to school or to go to the gym in the morning, then honestly,
Dean: it's not going to make too much of a difference. And if it does, you'll notice that your body will say, no, this isn't good for us.
Jono: Yeah, gotcha. Okay. Look, that didn't really confirm my bias, which I'm a bit upset
Dean: Ha ha
Jono: but that's good, right? That's what. So it sounds like there's potential benefit for, or maybe not so much benefit, but waiting that 30 plus minutes to get outside of that sleep inertia window to
Jono: actually kind of check in with your real time is because this sleep inertia kind of that presents itself as you could have had the most perfect
Jono: minutes anyway, is that sort of what that is?
Dean: Yeah, usually it's usually associated with which stage of sleep you wake up in. So if you're
Dean: keeping a regular sleep schedule, you should, if you wake up naturally, which I don't know what percentage of us do anymore, then you should be waking up in those lower stages of sleep, which shouldn't be associated with sleep inertia. That's too bad. But if you, for whatever reason, wake up and you're in that real slow wave sleep and you sleep inertia, which is a real issue for people like shift workers or people that work on call, firefighters
Jono: Yeah, okay.
Dean: and that sort of stuff. So that's another piece of research that's growing as well, how to get rid of that sleep inertia. But yeah, that's basically the premise of sleep inertia. So if you the best way to not have sleep inertia is to have regular sleep time and wake up sort
Dean: of at what time you usually wake up naturally and then you set your alarm for that time. Even if it's 10 minutes before you want to wake up,
Dean: then you
Dean: can get rid of that sleep inertia.
Jono: Is there potential for caffeine to help pull you out of that sleep inertia if you are woken by someone who's cool gets woken because they got to put out a fire or someone like me gets woken because of two-year-old jumps on them?
Dean: There can be a rationale for that. I mean, I think the only issue would be the time it takes for the caffeine to actually take effect might be just as long as the sleep inertia to dissipate. So
Dean: it could be a double-edged sword in that, well, once the sleep inertia runs out, the caffeine kicks in and you're happy days, but I don't think it will necessarily get rid of that sleep inertia straight away. There's some evidence
Jono: for watching.
Dean: there may be some, but yeah, it's still a bit of a growing area and outside of that on-call research area, sleepiness shouldn't affect you too much or be too detrimental for what you're actually doing. People are just usually moping around unless you're driving straight away when you wake up straight in the car, you shouldn't have to worry about
Dean: it too much.
Jono: Is there, is that potentially a bit of a caffeine takes 30 to 60 minutes to spike in the bloodstream? Sleep inertia takes 10 to 30 minutes to clear where maybe associating I feel better after my coffee when it's actually just
Jono: if you'd waited
Dean: yeah, certainly.
Jono: 30 to 45 minutes anyway.
Dean: Yeah, that's
Jono: Yeah, okay, cool.
Dean: that that could be the effect. So if you, um, now that you're who was listening to this might give this a go, the, they have that knowledge now, they have that knowledge now.
Jono:Definitely gonna be doing it.
Dean: Um, and yeah, if it's 30 minutes and you're sleeping, no, she's dissipated and you feel exactly the same, then you know, okay, I probably don't need that, that morning coffee and you could replace it with, I don't know. or a morning drink that sort of starts your morning, that sort of like psychological prompt that this is the start of the day. You can replace that with something else and then have your coffee a couple hours. I usually have my coffee as soon as I start my work day, which probably is an hour or two, or probably two hours after waking up. So it can actually fit with your schedule.
Jono: Yeah, yeah, cool. And then just for so I put I just realized that podcasts is basically an audio medium and I put my hand up before
Jono: saying I was gonna I'm gonna give that a crack I think because
Jono: I I definitely am have fallen prey to the get up you know often don't get to wake up my own accord so feel pretty pretty rough
Jono: most mornings and grab a coffee kind of when I can but
Jono: um with sleep
Jono: and ice off.
Dean: one with you and the smell of grinding coffee beans in the first thing in the morning is beautiful.
Dean: I mean, you could
Jono: nothing better. Nothing
Dean: still grind
Dean: them and just leave them there for a while.
Jono: Just do it.
Dean: But, yeah, no, it is, I think there can be a psychological aspect to it for some people. So if you can sort of replace that, that, yeah, behavior with another morning treat, I guess, if you want to call it that.
Jono: Yeah. And if I don't though, like, no, this isn't for like my friend. It's more, there might be people who are like, I, there's no way I'm going to do that.
Jono: Is there a big risk or is it more just you're not necessarily going to benefit from that coffee in that moment?
Dean: uh... do you mean in terms of replacing it with something else?
Jono: Sorry, no, if someone's like, I'm not replacing it, I'm still having my coffee within 10 minutes of getting up because that's my life. You can't take that away from me. Is there anything we need to worry about there?
Dean: I don't think it's going to cause any adverse effects. I mean, the buzzword at the minute is optimal. If
Dean: I had to choose between you having a coffee first thing in the morning or having a coffee half an hour before bed, by all means, have it first thing in the morning. Yeah, so if you absolutely cannot
Dean: and you tried it period and you can't do it then it's not going to result in anything untoward. But if you want to have the best effect of the caffeine based on what we know about its effects then yeah I would I'd say try it.
Jono: Yeah, cool. No, I love that. And I think I definitely am guilty of because there's this whole optimization out there. And it's probably been taken a little bit, I think it's taken too far. And optimization is presented as what should be the goal for everyone. It's easy to almost try and pull too hard in the other direction. And
Jono: like, you know, like not optimize anything. So I think it's good to know like, this is what our scale is, if you are looking for that last 1%, or this is an area do have capacity to change, then yeah, there's probably going to be an improvement, but it's not going to be the thing that makes or breaks your overall health
Jono: or energy levels by the sound of things like there's other, there's bigger rocks to focus on. Is that,
Dean: Yeah, 100%.
Jono: is that fair?
Dean: It's not, yeah, 100%. It's not black and white. And then if you read, that's the main thing about social media content is that a lot of the statements are quite black and white in that you must do this, you must do that. And people can actually be quite anxious about things if they don't do it. So this is a good example. Try and do it, even if it's a half now, wait, instead of straight away. Yeah, it's a spectrum. use the context that we're giving you to try and implement the principles as best you can.
Jono: Yeah, no one's going to click on that post
Jono: though. Go on, Dean. Like, yeah, it's which sucks because it's the actual, you know, correct approach.
Jono: But yeah, people love, they love camps, don't they? They love a binary. You must do this
Dean: Yeah, yeah.
Jono: kind of kind of answer.
Jono: But what can we do? So look, let's fast forward through the whole day. So we've gotten
Dean: Thank you.
Jono: up, we've gone through our day, we've had our caffeine. I wanted to ask just some big picture stuff about sleep because I've heard six to nine hours, seven to nine hours, I've heard six to eight hours. I think those are probably the main brackets that I've heard for optimal sleep. I've heard plenty of people and myself have been guilty of saying like, but I feel pretty good on like five to six hours sleep. I do wonder if those people probably including me are just like, don't know what seven to nine hours of sleep consistently feels like. So in And if so, what is that variability and how can I find out where I sit on that space?
Dean: Yeah, for sure. Again, context. But the recommendations, as you said, they sort of bounce from 7 to 8, 8 to 9. Anywhere over 7 generally is pretty good, if you can maintain that.
Dean: It's a pretty hard metric to, or I guess, requirement to ask of someone just based on daily life. I would say that would be low hanging fruit for people is to try and keep their sleep times consistent. Because you could be in bed for seven hours and they don't overlap. So if you go to bed at 11 usually and you wake up at six versus, and then the next day you might go to bed at nine AM and wake up earlier. Our bodies are very rhythmic. So even though you get seven
Dean: hours, you might not be getting the same amount of slow wave sleep and then you might feel different, even though you got the same amount of sleep.
Jono: Thank you. Ciao.
Dean: In terms of people that can function on less sleep, there is a study I always refer to back in 2003. Sounds like a long time ago, but this is something we tell our students a lot. Usually say, oh, that's study, so old, but it's a great study.
Jono: good study is a good study, right? Yeah.
Dean: So this is why we keep bringing it up. Basically they sleep deprived people, I think it was nine hours, seven hours, five hours, and they might have done a three hour condition, but that's proper deprivation. But basically what they found is people maintain their performance on the higher end, so nine and seven, but as you get to five, you do see a decrease in performance, at a lower capacity. So these people obviously went into the lab, they probably had nine hour sleep beforehand and then got a string of five hour sleeps consecutively. So the performance went down after the first five hours but then maintained. So if you're constantly getting that five hour sleep, you're maintaining your performance, but it's probably or likely at a reduced capacity to what you would be doing if you were getting nine hour sleep, but you won't know that because
Jono: Yeah. That's your baseline.
Dean: Yeah, correct.
Dean: With the lower end, it keeps going down, but if you're getting through hours of sleep, you probably know that you're getting through hours of sleep.
Dean: And then that rebounds pretty quickly as well. So if you go from seven to nine, it goes back up. That particular study did anyway. So yeah, in terms of performance, if someone does say, I work fine on five hours of sleep, then yeah, it's probably a slightly lower performance.
Jono: Yeah. And yeah, like I said, that's their baseline because that's just
Jono: what you're used to.
Jono: Right? So, and I guess that's also a good news for, like, and I think anyone who, like, engages with my stuff or your stuff will know that we're not going to be, we're not the optimal crowd. Like, we want to give people the tools to optimize if they have capacity, but also we understand that shift work, young, young, you know, young families, people on call, all those sorts of things are not going to be able to get a nice solid regimented seven hours every night. that that performance drops, but then maintains,
Jono: I guess, you know, it doesn't continue to climb across that. And it's also good to know that. So I think you said, once you move out of that five hours and get back up and to say the seven to nine range, it kind of pops back up pretty quickly.
Dean: Yes, correct, yeah. Yeah, so after
Jono: do you
Dean: study, they usually, when we do those type of sleep restriction studies, we usually do a baseline and then the intervention, so sleep deprivation or five hours of sleep and then a recovery sleep of nine hours or so and then someday you can see the rebound effect. So yeah, if you're
Dean: the week, if you work a job where you are getting five hours of sleep consistently, then you will maintain that performance a nine hour sleep or something after that you're going to rebound.
Jono: Yeah, so can I do that? Can I sleep? I mean, can someone not just me, this podcast
Dean: you. Bye.
Jono: just about me. Can you can someone say Monday through Thursday get five hours a night and then catch up? Can we sleep bank or what's the research there?
Dean: Yeah, you can sleep, it's not ideal. If you build up enough five hours, it's gonna catch up to you.
Dean: And there is a lot of inter-individual variability here in terms of five hours of sleep for me might be different to five hours of sleep for you. And potentially that dipping performance, my dipping performance might be a lot larger than yours. I would say yes, when you can, try and supplement your sleep with, if you can, we've done this with athletes, but there is some research with general population as well that you can supplement your nighttime sleep with daytime naps if you can. So if you get the same amount of sleep opportunity with night sleep and an afternoon nap, you get the same amount of total sleep. you can do that five hours at night and then try and get a couple hours in the afternoon or supplement that way but then yeah if you if you can only
Dean: supplement on the weekends then yeah definitely do that what I would say is try to keep your wake time consistent
Dean: Yeah, so
Jono: So earlier to bed,
Jono: but not... Yeah, okay.
Dean: which doesn't sound very appealing for like
Dean: the sleep in squad. I can completely understand that. But I think we'll probably touch on that a little bit later, maybe with sleep hygiene, how circadian rhythms work, but getting that sleep before you usually would, will make sure that you're not moving your body clock too much, your behaviours. can do
Dean: that but at the end of the day I'm on team more sleep so yeah
Jono: Right, yeah, so that's like step one,
Jono: get as much as you can,
Jono: but then there's ways again to kind of optimize. I didn't know that about, well, I'd heard mixed reports about napping and I don't know enough about this sort of area to do my own research. And you wish I need to note, you've literally done your own research, right? You've been involved in a bunch of sleep studies, which is
Jono: awesome to speak to someone in the, who's actually doing the research. But so catching up on the weekend, but still probably better than just not catching up in general.
Jono: But napping a better strategy when when able.
Dean: I would say so. It's just a safeguard to basically not have an extended period of time where you're getting less sleep than you need. So even
Dean: if you can get, if you're doing those five hours during the week and you can't possibly get any more sleep and you can do that nap even once or twice that week, it's going to be better than, well that builds up because a weekend, sorry, each day of the weekend, then that's an extra four hours. But if you can sneak a couple in during the week, then, yeah, that study we actually did
Jono: up quick.
Dean: in our lab, the NAP study, which was awesome. So we supplement, we gave them different amount of sleep during the night, and then the different amount of sleep during the day, always ended up being nine hours total. But there were no differences, but
Jono: Yeah, cool.
Dean: differences at all between the sleep metrics. And that's probably something you'll probably find You see a lot of, again, tweets or Instagram posts about how we can improve our sleep or change our sleep. In healthy sleepers or healthy individuals, in our lab we have to do, we don't very often see a large effect of any intervention in our lab. It's
Dean: quite hard to run a study and see a large change unless you're running a a night shift protocol or something where you're sleep depriving them. But yeah, it's actually quite hard to elicit a meaningful change in sleep when you're measuring it as precisely as we do.
Jono: Yeah, right. So unless you're doing, like you said, the night shift. So something, unless you're aggressively disrupting someone's sleep,
Jono: it's a yeah, okay. I and I would not have guessed that with napping. I would have been like, no, it's not as good. Definitely not as good.
Jono: So there you go. That's why I don't trust my God all that much. So good news for you nappers out there.
Dean: I'm a terrible Napper by the way, so if... yeah. Yeah, I'm not a great Napper, but if you are, by all means go for it.
Jono: Yeah, so it's a super. What's the word? Why can't I think I need to have a nap?
Jono: Clearly. Yeah, yeah. Anyway, it's now I can think about is napping. But anyway, my son's a great napper. But
Dean: Yeah, well,
Jono: I think by the time he's down, I'm like, right, I'll have a
Dean: oh, maybe not your time, but post-lunch dip is usually, then, if
Jono: Good time
Jono: for an
Dean: effective food, there's a little dip in our circadian
Jono: yeah, yeah.
Dean: is when we usually get a bit sleepy. So, yeah, if we, if we stutter or we can't get a word out, blame the, the,
Jono: Yeah. Yeah. Need a siesta. Right.
Dean: That's it.
Jono: So look, let's say that I can't get enough sleep due to work or yeah, shift work, kids, something along those sorts of lines. Napping seems like the first line of defense trying to catch up there where we can and then trying to catch up on later days, you know, whether that be the weekend or days off different shifts from parents. Is there anything else I can do nutritionally or lifestyle, things I can do during the day, or I guess, things that don't involve increasing my sleep hours?
Dean: Yeah. Now, in terms of nutrition, I'll give a shout out to one of my colleagues, Dr. Charlotte Gupta. She does a lot of work in, it's actually one of the cooler names of an area, chrono nutrition.
Dean: Yeah. So she does a lot of work around shift work and meal timings, what make up of certain foods, the shift work. So if you're a shift worker, I definitely recommend searching Dr. Charlotte Gupta on Twitter. there. Slightly left of my area, but in a rough nutshell, when your body is preparing for sleep, we want it to be preparing for sleep, not digesting burrito,
Dean: late night burrito
Jono: yeah. Ha
Jono: ha ha.
Dean: So in terms of, get your meal times consistent, and then if you have your pretty dinner snack that's sleep in terms of your body's digesting instead of sleeping, then yeah I would keep it to a minimum probably within the two hours, three hours leading into bed but again people have kids, you have other commitments, just try
Dean: and do
Dean: your best.
Jono: where you can.
Dean: Tryptophan rich food, probably people have seen that a bit. We have done a bit of nutritionally Put together sleep drink that helps people sleep and tryptophan being one of the ingredients A-lactyl boomer, I don't know if I'm saying that right, but it's a it's a protein found in in milk Which does have some evidence so we actually found that it reduced sleep onset latency Which is basically the time it takes to fall asleep
Dean: that a glass of milk before bed helps you sleep
Dean: because that protein is found in milk. So there is varying evidence around different foods, kiwi fruit you can have before bed. I usually have that just because I love kiwi fruits too. Skin on.
Jono: Ah, we're gonna have to end it there
Jono: Everyone, I'm so
Jono: sorry. No.
Dean: But yeah, a lot of the stuff around diet or not so much the content, I won't go that deep just because I guess it's not my particular expertise, the make-ups of the meal. But it's pretty common sense in terms of let your body do what it wants to do when it's going to sleep. That's probably my
Dean: rough recommendation. in terms of the morning, but
Dean: there was just a recent systematic review which is basically for those who don't know, it's a study that collates all the information on a certain topic from other studies that have previously been published. So it's one of the best forms of evidence you can get. And basically they looked at the amount of caffeine people are taking in and how that affects their sleep. And if you're a caffeine lover, don't listen right now
Dean: It's not great news, basically the general recommendation and I'll say this under the proviso of there is some individual variability in how people metabolise caffeine as you would know. But basically the recommendation is last coffee about nine hours before bed, 8.8 hours before bed to not input
Jono: Nine, oh, okay, that's, yeah.
Dean: It's a lot. Yeah. So basically, we're not giving you much of a sweet spot. So two hours after bed, two hours after working up, nine hours after going to bed. But then for those who love a pre-workout, it's actually worth, it's actually 13 hours before bed is the recommendation. And I know that's probably not,
Dean: it's probably not feasible for some people that train in the afternoon. And I, as I would say, for the other things that we've spoken about is, affecting your sleep noticeably and you're having it early enough that is coffee and pre-workout. Try having less or try doing less but yeah just have that in mind the pre-workout does have quite
Dean: an effect.
Jono: Is that because of the higher caffeine dose or is it the form of caffeine or is it just the milligrams?
Dean: Yeah, it's a milligram. So I think relative to coffee, coffee is about 100 milligrams per 250 mil. And then
Dean: pre-workout is probably, yeah, I think it might even be double that. If anyone wants
Jono: seen a four to 500 milligram scoop
Jono: in some of the crazier
Jono: ones like
Dean: So if anyone wants to
Dean: that one, that one is actually written by a great PhD student in really, I think, uh, yeah, Brzee said, um, Carissa
Dean: Gardner upper ACU. So that's a, that's a very interesting read. It's got nice pictures as well, which, um, yeah, it's good, good
Dean: for my brain. Um, so yeah, that, that's,
Dean: that's very recent recommendations only in the last couple of months. So, um, yeah,
Dean: so sorry everyone.
Jono: No, well, look, I am the other thing I would just say as well, if you are someone who trains in the afternoon and being pragmatic about caffeine consumption, of course, but often what I find is people aren't fueling nutritionally particularly well before they train and they're using that caffeine hit as a bit of a bit of a crutch.
Jono: So if you feel like you can't live without your pre-workout before every session, that's also probably another bit of a red flag on total
Jono: and but I do think that right before you train, maybe have a look at your pre-training nutrition as well and you might find that you don't need that pre-workout before arms and core. Right? You know.
Jono: So yeah, okay, that's good. So I guess realistically for most people that's a soft cutoff or a firm cutoff of
Dean: Yeah, lunchtime coffee, which I try to stick to. I mean, even as a sleep scientist, I'm not perfect sometimes. I eat 2 p.m. and I'm like, I need a coffee. And
Dean: I sleep well, so always come back. You can, whenever you're asking yourself a question related to sleep, if you're a good sleeper, you're not tired during the day. You don't have any daytime sleepiness at all. And you err from once or twice a week to once, don't have to stress. But if you do, you if you say I'm gonna have a coffee today at 3 p.m. and you are wired then act
Dean: accordingly. Because we're all at the end of the day, we're all end ones, we're all our own experiments basically. And that's the most important answer really. So if you keep track of how you're feeling, what happens to you, what you did that day, if you're wired, you can't get to Maybe that will again.
Jono: Yeah, so that is reliable. We are like how we feel and our own, you know, that we're not going to skew that at all.
Dean: Yeah, I mean, listen to your body is probably the one of my main things that I say in saying that sometimes when we look at subjective measures in research, they can be quite wrong in terms of sometimes
Dean: we ask people in our lab, oh, how long do you think you slept for? Because they might be blind to the condition. And they say, I slept for four hours out of terrible sleep. And they sleep
Jono: Yeah, well.
Dean: if you're feeling consistently sleepy during the day when you shouldn't be. And it is hard to tell sometimes between fatigue, whether you're just having a really fatiguing day or whether you're actually sleepy. If you wake up sleepy. So yeah, it's a bit of a trial and error in terms of acknowledging how you're feeling, whether that can be related to a behavior during the day
Dean: So again, I'm giving an answer, a layered answer, but yeah, I would say your body gives you the most information, so listen to it. Or learn, I think I was going to touch on this a bit later, but investing in knowing how your body works is, is awareable in itself. Because you know,
Dean: is probably why I'm not feeling great. And if that is sustained over a week or two weeks, then it's pretty good chance that the thing that you're thinking of is the mechanism.
Jono: is the thing. And that's an important point as well, I guess, like you said, the fact that because there's so many other factors that could be influencing, like you said, it could have just been a big day, you could be stressed, there could be other things I think don't try it once for one
Jono: day and go, ah, see, I knew it. That's not the problem. You know, I still feel bad anyway.
Jono: So one thing I've heard is caffeine may not affect people's ability to fall asleep, but can affect cycles and more restful sleep cycles. Is that legit or is that
Dean: I don't have a concrete answer on that in terms of the way I may just have not read that research, but the mechanisms, if you just think of it that way, is so there's two, without getting too sciencey, there's two ways that sleep is regulated. Basically, it's the system we spoke about before. Basically, when we wake up in the morning, the adenosine is building up in our brain, pressure for a small period of time. When that dissipates, that's when you get the coffee crash. So that's, it doesn't get rid of the adenosine, it holds it off. And then when the caffeine goes away, it goes,
Jono: Yeah, it's like a wave
Dean: yeah, it's a wave.
Dean: you get hit with all this adenosine and that's what a coffee crash is. So caffeine is affecting that system. And then the second system is our circadian rhythm. our body primes for sleep at night. It basically follows our core body temperature rhythm. So as our body is preparing for bed, our core body temperature is going down, probably dips around 3 to 4 a.m. and then goes back up as we wake up and is high during the day. And that basically is probably the main mechanism that controls our makeup of our sleep. So it knows what time of day it REM sleep. So
Dean: I would, I would, without being completely confident in all the research I have read, I would say I would err towards caffeine keeping you awake rather than impacting your sleep stages too much. In saying that, follow the recommendations and neither will be a problem.
Jono: Yeah, that's true.
Jono: Stop trying to find loopholes, Jono. Is that that's... I'm just trying to look. Most of the loopholes are coming from me. I'll admit that. But also definitely the clients who
Jono: are like, I have a coffee right before bed and I feel fine. You know, sort
Jono: you know...
Dean: there is also a tolerance level. So
Jono: Mmm, okay.
Dean: they may actually not be a validated answer to that question in terms of people that are really, really used to having coffees. And I know I go out with my wife's grandparents and I'm just about falling asleep at the dinner table when they
Dean: there is individual individual variability I would just say try not to do that
Jono: Yeah, yeah, yeah, I like I probably I am a healthy caffeine consumer.
Jono: But the thought of having something, yeah, around bedtime or after bedtime, I'm like, I can't,
Dean: Thank you.
Jono: can't fathom it. But yes, the I think, like you said, those recommendations are there for a reason trying to buy by them slash do that couple of weeks of investigation, maybe
Jono: you get to get clients or around
Jono: how they feel, their sleep cycles, all that kind of stuff.
Dean: Yeah, we generally start out with whenever we do a like a baseline measurement of someone's sleep behavior, we give them a sleep diary and then whatever associated device we might be using to confirm their sleep patterns. So yeah, if you're not. I'll save this first thing and then I'll give a caveat in that if you're not measuring it, you don't know what's happening.
Dean: in your diary that you have each day, write down how you're feeling, how you slept. It doesn't have to be hugely scientific. But then on the other end, if you do have a wearable or something that has the capacity to put in your behaviors and how you're feeling, by all means use it. Try it. If you don't like it, you don't have to do it. So some people love tracking certain variables and some people hate it. down or tracking yourself and your behaviors then literally just write it down on your diary how you feel each day or that you had a caffeine coffee at a certain time and start there and if you want to keep growing that you can get pretty in depth with it these days
Jono: Yeah, well, definitely a big bunch of questions I had for you was around wearables,
Jono: because I know that you've done a lot of research in that space and they're becoming more prevalent. And of course, as technology improves, they're getting fancier and fancier. you guys using a
Jono: lab, I guess consumer grade, I can walk into a JB high fight. Are there still different grades that I should be looking at?
Dean: We can use wearables as a term. There are levels, I think, in that the market, listen to me, it's like an economics podcast, but some are a device that you go and you outlay and you buy the device and it comes like that. And then there's other devices where you sign up for a subscription and you get the device as part of the subscription. So they're all technically wearables. And then there's another layer to that, we really need to go into, which is like a partial polysomnography system, which is what we have in the lab, but you can have it at home and just whack it on your forehead. We don't need to go into that, but
Jono: Yeah, right.
Dean: we can talk about wearables as a whole and the different levels, because they're basically doing the same thing, but slightly differently.
Jono: Yeah, gotcha. And so I guess I've gone into a shop, I bought a wearable, you can mention brands, by the way,
Jono: I just don't mention any because I don't know any.
Jono: But I know the big ones. Like let's say I've grabbed a wearable, what numbers should I be looking at or what ones are valid?
Jono: slash, you know, just what can we measure actually properly? Because I'm from my perspective, I know that total calorie burn throughout a day is not a really valid metric
Jono: that comes from those wearables. We know there's a ton of variation there, but in the more sleep recovery, resting heart rate,
Jono: all of the other things I don't understand, what are some good numbers for us to be looking at coming from our wearables?
Dean: for sure. I will I'll preface this with the statement that we do our lab do work with a few of these companies in full disclosure so that way influence my answer at all because we have done validations on each of them. So basically any of the devices I guess the wrist worn, the finger worn in the rings and there's a few of them now so I'm not specifically talking about one of them. hard to get out, where the little lights that you see on the devices basically reflect into your veins or bloodstream and detect your heart rate. That's the first premise and then they also use movement to score whether you're moving or whether you're lying down. And the original devices we use called actographs was just the movement. So you get zeros and ones person was moving or not and that
Dean: was pretty reliable. The difficulty with wearables or something that isn't measuring your actual brain waves, so anything that isn't on your head basically, are assuming a couple of things based on movement and your heart rate. They measure sleep very well so if you ever see a metric, usually it's called sensitivity They're usually high, they're usually in the 90s. But always try and contextualize that around, if I know that you John O. sleep for seven hours a night and you're a healthy male and you're probably going to be sleeping for upwards of 90% of that sleep, I can take a pretty accurate guess without putting a device on you for how much sleep you get.
Jono: Ja, kocha.
Dean: in measuring the sleep. The difficulty and kind of where the better performing wearables are more obvious compared to the others is the wake. So how well do they detect the wake in between the sleep? So it's hard to tell between restful wake, I don't know watching a movie in bed, reading in bed, and restful sleep. So when you're trying to fall asleep, or when you wake up in the So those, the devices we, well probably the mainstream devices range from 20% accuracy or sensitivity, there's a few words that people use but it doesn't really matter what word you use, 20% to around 60%, 60% accuracy
Dean: or whatever you want to call it for wake. So if they're around that 60% mark, it's pretty good. that has six different wearables that we tested. It was a hell of a study to put together, but
Jono: 아, 진짜.
Dean: that gives you the context. So what I would say is if you have a wearable, you're measuring sleep specifically, then I would say look at your total sleep time, but also look at your sleep timing. I briefly touched on it before because we wanna keep that consistent. time constant and your wake time constant. If you have to choose between one or the other, keep your wake time constant. In terms of sleep staging, they're getting a lot better. The bed up of,
Jono: Okay. What is sleep staging?
Dean: yeah sorry, so basically when we score sleep in the lab, we score it in stages ranging from wake to light sleep. There's a few, so we call it N1, N2, N3, which is slow You might have heard that. And then there's REM, which is the dream stage. Basically what we do is we put all these devices on people with our system. We get professional people to score the sleep. So what happens is we get a registered technician. They go through every 30 seconds of each sleep. It's a lot of sleep.
Dean: Yeah, it's very manual. And they categorize each 30 second chunk to N1, to which is also like sleep or slow sleep or REM. And then we line up our gold standard and whatever device it is, and we compare what they're saying at that certain time. And that's how we get those numbers. So when we talk about sleep versus wake, it's wake and all of those stages lump together. And then when we talk about stages, it's those specific stages. So that's a different comparison. So we're basically scrutinizing the devices a little bit more. They, the better performing ones run at about 60 to 65% for all the stages, which is, it's quite impressive given that they're just measuring things from the wrist or finger and they're
Dean: not a person scoring it. And even when you compare across scorers, so people scoring the same, PSG gold standard sleep data. We don't get a hundred percent agreement. It probably sits
Jono: What's the intro there?
Dean: a writer
Jono: it into very
Dean: it's around yeah,
Jono: in interact?
Dean: 80 Yeah, so
Jono: Okay, yeah.
Dean: it you can't the variables will never get to 100 So sitting around 60
Dean: is relatively good in saying that I don't think you need to take too much notice of it
Dean: if you do want to use it, and this could be getting a little bit physiology based, but
Jono: I had to do it, dive in.
Dean: if you see a sustained change, for example, if I'm wearing a wearable and I've been getting 15% of slow wave sleep for the last six months and then for a month I'm getting 2%. and be. completely accurate in terms of your slow wave sleep is changing, but it is detecting a change in your physiology of some sort.
Dean: So something's
Dean: It may be completely correct. It's just hard with wearables to validate that. So I would say if you're looking at your sleep stages and they're consistent, happy days, don't forget just check your And yeah, keep it like so. I wear wear I've won all the wearables and I check in not every day If something if something
Dean: went wrong or I feel tired, then I'll go back and look But yeah, I would say look at total sleep time and then Move from there if if you do if you're finding yourself again another layer of context quickly as I'd like to, if it's taking you 20 to 30 minutes or more to fall asleep, then there's a different way you should use the wearable. And this is something that is pretty low hanging fruit. So most of the devices now use automatic detection. I don't know if you wear one. So if you go to sleep, you don't have to push anything. Say you're going to sleep, it'll just get, well, guess, okay, they've stopped moving. They go to sleep now. It's actually really hard to know when someone is attempting to fall asleep.
Jono: Yeah, yeah.
Dean: So if that's something you want to look at and you want to measure that, I would suggest, I think most of the wearables do this now, either starting manually, starting asleep. So in most apps, you can go in and you can say, start I'm going to sleep now. And that gives that anchor point. And then it will give a relatively accurate measure for how long it takes you to fall asleep. If your device doesn't do that, then almost certainly you'll be able to edit your sleep. So if your device doesn't have the prompt to start a sleep, write the time down that you actually are going to attend to sleep and then edit it the next morning. It's a little labor intensive, but to accurately get that answer, that's probably the best protocol to use.
Jono: Yeah, awesome. So we've got, we want to be paying attention to sleep duration,
Jono: times of sleeping, like sleep and wake, I guess. Got that little hack for, that's great for getting some slight, a bit more accuracy around sleep times. A big thing I see a lot is the metrics or the ranking of recovery in a lot of these wearables, you know, ranking your recovery out of a hundred or something like that. and people online just saying, my wearable has said I'm under recovered today. And so I just did a light session. How valid is that?
Dean: It's a tricky question, because, yeah.
Jono: I'm sorry, yes, I'm
Jono: it is. So
Dean: I knew
Dean: it was coming.
Dean: The problem, or the difficulty I'll say, it's not a problem as such, but a lot of these metrics are proprietary in that we don't, the end user doesn't actually know
Dean: is going into that number. The companies might give a short description But for the most part, it's all proprietary. What I would say is, they happen, we did a study with one of the wearables looking at those proprietary metrics, the training load, and they do follow the pattern. So obviously these companies are investing a lot of money into this research. So it's not
Dean: something you discount completely, terribly recovered and you're feeling great, the answer is probably somewhere in the middle. I would say, but if you're looking at the raw metrics, they're probably gonna provide more context to that number as well. So people talk a lot about HRV, heart rate variability, which
Dean: is one of the main metrics that those scores or composite scores will base their result on. If you want to follow a very good practitioner with HRV, Marco Altini, he writes a lot of blogs around heart rate variability. The problem with that metric is a lot of the companies do it differently. Yeah, so in a nutshell, it's a measure of your autonomic nervous system. is that rest and digest, sympathetic is like the stress response. So the higher your HRV, and this is a most important thing, relative to your baseline. been more recovered you should be. So a higher number of HRV shows that there's a healthy imbalance between the two systems. So the stress you're adequately armed to respond to stress, but you're also recovering from whatever previous stress that you put the body through, if that makes sense.
Dean: So that's
Dean: probably, I would say, look at that first, and then want to look at the competence score you can. But I'd say invest some time into understanding heart rate variability a little bit more. Same with sleep. If you increase your literacy on what these numbers actually are, then you'll be able to adequately respond to whatever feedback you're getting and then if you need to change your training. I mean the big piece with these ones, and I alcohol.
Dean: When I first started wearing these wearables or using an app like Marco Artini made HRV for training if people want to use that, if they don't want to buy a wearable. The sensitivity to alcohol is insane in terms of I can have a one beer on a Friday night and I know we've exchanged quite a few DMs
Dean: you'll just tank your numbers. And it makes you
Dean: want to not
Dean: drink anymore. I'm not saying don't drink it.
Dean: It's very telling in terms of what it does to your body. And that gives you a bit of context
Dean: to how these numbers work and what they're measuring, I guess.
Jono: Yeah, gotcha. Yeah. So it sounds like the I need to go buy some more not the best alcoholic free
Jono: beer, just
Jono: so everyone
Jono: knows. Not sponsored, not affiliate. Oh, man, I say I wish but I'd still have to say
Jono: But of all of the if a company was to reach out that would be one of the hardest to say no to I think but no. So these the feedback I'm getting from those wearables full disclosure, I've actually
Dean: Yeah, and that's okay.
Jono: I don't have personal experience with it. But from it sounds like there's good validity in that it you want to take notes from it and you want to take, yeah, but not let it run your whole training, run your whole life. You want to sort of
Dean: Thank you.
Jono: take some prompts and run that through
Jono: your filter.
Dean: correct. There's there's there's heaps of value in in the in the outputs. And you can use that to inform things to whatever level. And but then also it's still listening to your body as well. Like we during during COVID, we didn't have a lab. So I worked with one of the where books companies to use those metrics to detect COVID. And the metrics are super sensitive stuff like that. So we could tell someone predict
Dean: over days before they exhibited symptoms. So there's a range, again, it's a spectrum. But
Jono: w ild.
Dean: yeah, it was a very interesting project. But so if you listen to your body and you can lean on those numbers, I'd say look at the raw numbers first once you understand them, and then you can sort of gauge with the composite scores, the percentage of schools, or if you don't wear a wearable, you're sleeping well, you're training well, you're happy with your progress, you're hitting your goals. You don't absolutely need one. It could take you to a next level. You might love it, who knows, but don't be, don't stress if you don't have one, it's basically what I'm saying.
Jono: Yeah. Oh, I just hate things on my wrist.
Jono: Like I wish
Jono: I could
Jono: a watch because I think watches look cool,
Jono: but I just, I just don't, and then like even I've got a wedding ring and that's annoying enough
Jono: to take off when I train. So the thought of like a, so I'm just, I'm just a suck.
Dean: Ha ha.
Jono: That's really what it is. Like I, I haven't ruled it out by
Jono: any means, but, um, it's good. I think it sounds like as always, people want, should I just listen to the human or should I just listen to the machine? And the answer is like, well, both
Dean: no, for sure. And then there's another layer to it in that you're either an informed human or an ill informed human. So if you don't know how
Dean: any of these mechanisms work or how your sleep works or training loads or dietics or what you're eating, then you're not informed to listen or act. validated wearable making decisions based on both.
Jono: So if I find if I start wearing a wearable says my HRV is low, but I have no idea how to impact my HRV. That's not Super
Dean: it's not,
Dean: yeah. And then the other
Dean: thing is with metrics like HRV, is I might have a really high HRV, and I'm just a local punter that goes running on the weekends. And then there might be an elite athlete with a lower relative HRV.
Dean: Yeah, so it's all about deviations to your own baseline. pretty much all health related metrics, that's what you should be looking at.
Jono: Yeah, oh, you think like testosterone,
Jono: right? The amount of guys that stress about testosterone and then people who have plenty of muscle, plenty of libido and energy and mood, they're on the low, quote unquote, end
Jono: of the
Dean: obviously, there's thresholds and things that are medical.
Jono: Of course
Dean: I'm saying,
Dean: for the context of wearables and sleep and that sort of stuff, then yeah, it's the deviation up or down from baseline is really where the money's at. Well, not the actual money. Yeah.
Jono: No, that's the, well, okay, so last question, sorry, cause I'm conscious
Dean: Yeah, yogurt.
Jono: of time, but we keep referring to
Jono: baseline. How do I find out my baseline? Like, so with say, if I do start tracking my HRV, how do I know, do I just let it run for a few months and then can trust that that's my baseline?
Dean: Yeah, I think Yeah, you'd want to get an extended period of time and then obviously contextualize that with what you're doing so my HRV
Dean: for example, which should be for most people that If I stop training for a week my HRV will go up and then if I'm doing a lot of high intensity work It might go down a little bit, but you want it to maintain basically for that metric in particular For sleep, it's a two week window we usually get the baseline for. And yes, a wearable, that's validating is probably the best way to do that, but you could do it with a sleep diary as well. But yeah, I would give it at least
Dean: a couple of weeks. And then ideally, if it's training specific for people, then you would maybe try and do or like a whatever fits in their schedule, but it's not really, it's not feasible with some people. So I would just say... contextualize things.
Jono: Do you just want to make sure I guess that it's not two weeks after the birth of your
Jono: first child
Dean: I mean...
Jono: When that project at work is due or you're traveling or something is that not
Jono: gonna give
Jono: a yeah
Dean: And but that doesn't mean you don't have to measure it. You can still measure it but contextualize that baseline based on what you're doing. And then it's actually a way that you can sort of validate it to yourself. If if you're going through a real stressful period, I don't know, promotion or having a child or whatever. And then a few months later, things slow down a bit and your HIV rebound goes up relative to what you were. of validates that, okay, what the protocols that you're using to measure that metric are making sense based on what you're doing and then providing that context around
Jono: Thank you.
Dean: it. So that sometimes the low hanging fruit is adding the context to what you're measuring and that validates it. Like during my PhD, it was crazy and I had like a breakdown,
Dean: not like a mental reflected that.
Jono: Yeah, well,
Dean: So it can be a
Dean: tool and then you can use it to work your way back up again. But in saying that, you can just listen to your body too.
Jono: Yeah, yeah, but I mean, like you said, I think I can definitely see value in there
Jono: both, you know, refining the information you're getting from the wearable and running that through that filter of how I
Jono: feel. And so I guess like any tool learning to
Jono: use it right.
Dean: and then if you're like yourself, John, know that doesn't want doesn't like wearing wrist watch or a ring.
Jono: Suck it up.
Dean: No, in terms of in terms of HIV, obviously the best way to measure high rate is a chest band. So HIV, what are
Dean: the main protocols? Prior to the explosion of wearables and is still used by a lot of athletes is measuring first thing in the morning. that you could not change too much about your life and still just wake up in
Dean: to a one-minute test. There's apps you can use it you can use your camera phone, put your finger over the camera phone and that measures your HRV. So that's another... so you can tailor your wearable or your tech tools to not change your behavior too much if that's a deal breaker or something that won't schedule or whether you want to sleep with a wrist watch on. You would have hated my study when
Dean: we ran with six different devices at the same time.
Jono: I was gonna say,
Jono: was that at once?
Jono: Was it just like boom, boom, boom?
Dean: Three on
Dean: each, three on each stretch.
Jono: of nightmares.
Dean: yeah, it was one on the
Dean: forehead and a ring. So you wouldn't, we might have exploited you, I think, Matt.
Jono: I definitely would have, yeah, I either wouldn't have been accepted or I would have been one of the dropouts for sure.
Dean: Fair enough.
Jono: Mate, thank you so much. It's been, there's a stuff that I'm super interested in. And I think we all should be right because recovery and fatigue management and sleep and sleep hygiene and all of the things like we, yes, I know we started with a bit of a joke around people communicating very black and white facts about sleep. Indisputable things is it's very
Jono: important, right? So it's really interesting to find some little hacks of the nap thing. Maybe I should revisit that and try and get better at napping because that's
Jono: great. And all of the wearable discussion.
Dean: try the Nappuccino, everyone loves this one. There's limited evidence, yeah,
Jono: Oh, yeah.
Dean: but if you struggle with mapping, this might be a way to incentivise it. Early afternoon provides though, but have a coffee, nap for 20 minutes, by the time you wake up, the coffee will kick in, get rid of your sleep inertia, so you can have a go with that one if you want to.
Jono: I mean, just another excuse
Jono: to have a coffee. So you're right, that is a good incentive. So yeah, another hack. And then all the wearable talk is a lot of noise out there about them. So it's cool to figure out what is relevant and useful and
Jono: how to, again, I think, like we said, it's a tool. So learning how to use that tool is
Dean: That's it.
Jono: really awesome. So if people want to learn more about you, about the work you're doing, about the studies you've discussed, I will actually like pause. I'll put all the studies that we've discussed in the show notes on the website those and I'll of course link up to where you can find Dr. Dean. What are you going to call
Jono: you Dr. Dean now? Call, where you can find Dean. Where's the best place that people want to engage with your content and your research?
Dean: So I'll be, I'm on Instagram and Twitter, probably more on Twitter. I'm trying to find more time to do, to do the Insta stuff, but just at Dr. Dean J. Miller. If you want to go into a bit more depth in terms of the research articles, if you want to dive deeper, obviously Google scholar or research gate, you can just type in Dean J. Miller. I'm the only one. That's why I put the J
Dean: in It should suffice otherwise, yeah, I'll try get some more stuff out on Insta for you guys
Jono: Awesome. Thank you. Yeah, I'll link the Twitter. I'll link the Insta, I'll link the research gate and we'll link those studies in the notes. But Dean, thanks so much for coming on today, mate. It was a blast. Got to ask you all the questions that I wanted to ask you, which is really what's about,
Dean: worries at all. Now it's great. It was awesome. Now to chat.
Jono: Awesome. Thank you. And thanks guys for listening. I'll chat to you next time.
Episode Links & References
- Instagram - Dr. Jean J. Miller
- Twitter - Dr. Jean J. Miller
- ResearchGate - Dr. Dean J. Miller
- The effect of caffeine on subsequent sleep
- Patterns of performance degradation and restoration during sleep restriction and subsequent recovery
- A Validation of Six Wearable Devices for Estimating Sleep, Heart Rate and Heart Rate Variability in Healthy Adults
- Daytime naps can be used to supplement night-time sleep in athletes