The Decibel - How sleep affects our brains

Episode Date: March 28, 2024

There are few more important habits for human health than the hours we spend asleep every night. Research shows sleep – or lack of it – affects everything from our physical and mental health, decision making and ability to fight illness. Despite this, at least one in four Canadians say they’re unhappy with the quality of their sleep.Dr. Rébecca Robillard, neuropsychologist at the University of Ottawa and Co-Chair of the Canadian Sleep Research Consortium, goes deep on the science of sleep and why it’s vital for cognition and brain health.Questions? Comments? Ideas? Email us at [e-mail]

I've always been intrigued by the connection between mind and matter, like the biological substrate of what we're experiencing. Sleep expert Dr. Rebecca Robillard is fascinated by the mysteries of sleep. Like how those electrical impulses and biochemical shifts in the brain actually translate in experiences and how we think, how we feel, how we perceive the world around us. And I guess one striking reminder of that connection between mind and matter is the fact that, you know, those experiences change across different states of consciousness.

This is exactly what happens during sleep. Our brain does not just like shut down, it enters a whole different world, both from a physiological perspective and also an experiential perspective. Science is only starting to put the pieces together, both in terms of how sleep works and why it works the way it does, and why it doesn't work for a lot of people. According to Statistics Canada, a quarter of Canadians say they're unhappy with their sleep. But as research continues, one thing is becoming clear. As I was progressing through my training, both as a neuropsychologist and as a sleep scientist, I really came to understand how foundational sleep is to so many aspects of both mental health and physical health.

Dr. Robillard is an associate professor at the University of Ottawa and also the co-chair of the Canadian Sleep Research Consortium. Today, she'll tell us about the science of sleep and explain how crucial it is for our cognition and mental health. I'm Mainika Raman-Wilms, and this is The Decibel from The Globe and Mail. Dr. Robillard, thank you so much for being here today. My pleasure. So I think we should start off today by talking about what we do know about sleep. And specifically, I want to ask you about the different stages of sleep.

So what is happening to our body and also to our brain as we move through the different stages of sleep? Yeah, that's a really fascinating story. So as we're awake, our brain activity is at a quite high frequency and rather low amplitude. That means that our brain is generating, say, 50 or 60 small waves every second. And that reflects the activity of the brain cells underneath the skull, which basically shows that all of these different brain cells are firing at their own kind of pace. And then as we're drifting into sleep, we see that brain activity starts slowing

down. So we generate waves that start getting a bit bigger and about, you know, one to eight times a wave per second. So our brain activity is slowing down. We see this slowing down in our respiration as well, in our heart rate. We see respiration and heart rate becoming more regular. And our eyes might start rolling slowly from one side to the other. And if you stalk your bed partner at night when they're trying to fall asleep tonight, you might even be able to see this movement underneath their eyelids. And then I guess as we're kind of getting into deeper and deeper sleep, those waves get slower and slower. And that's something quite intriguing and drastic that we

see happening in deep sleep, which we call non-REM sleep, non-REM stage three sleep, for example, where the brain suddenly starts generating very high and large slow waves. And this is because there's hundreds of thousands of neurons or brain cells that suddenly start, you know, acting all in tune. So they fire together at the same time, then they go silent at the same time, then they fire again and silent and so on. So they're getting into that synchronized state that makes it so that the sum of all their activity reaches a much higher peak than what we see during lighter stages of sleep or during wakefulness. So it's not at all that the brain is not active during sleep. It's really that it's behaving in a way that's drastically different

than what we see in other states of consciousness. Fascinating. Okay, so that's deep sleep. What happens after that? Another really interesting stage of sleep, we were talking about REM sleep or rapid eye movement sleep, that stage of sleep where we see the eyes, they're not doing such so much of a slow side to side movement, but these kind of rapid kind of jerky movements. And we call that paradoxical sleep also because when we look at what happens in the brain during REM sleep, we see that brain activity becomes very similar to what we see during wakefulness. So we have those fast, low amplitude waves that, you know, kind of gives us a hint that, you know, the processes that are going in the brain might be similar to what is going when we're out there experiencing the world. So REM sleep, of course, is when we're dreaming, right? So this is our brain doing all of this

stuff while we're still lying there. Exactly, exactly. But then we actually don't do these things. We don't act upon them because our body is essentially paralyzed. So we do have those elaborate kind of vivid dreams during REM sleep, but we also have other types of mental activity as well during non-REM sleep as well that might kind of take a slightly different kind of shape. Oftentimes, it'll be like more of a thinking about concepts or shapes or colors or something less elaborate during non-REM sleep. So altogether, we've got basically non-REM 1, non-REM 2, non-REM 3, so increasing progressively in depth, and then REM sleep. We cycle through a lot of these sleep stages. And this is intermixed with periods of mini periods of wake if you want. So overall, we'll go through, you know, four to five cycles of, you know, non REM sleep stages and REM sleep stages across the

night. So it's not that we start in, you know, light sleep, and then go in deep sleep, and then REM sleep, and then wake up, like we really cycle through multiple, multiple times during the night. So interesting. Yeah. Okay. And I want to ask you about, I guess, how long we need to sleep, because we kind of hear this universal standard of seven to nine hours of sleep each night. But I guess I wonder, how much does that actually vary from person to person? Yeah, that's a great question. And, you know, we hear that a lot. And it is true, like if we look at big epidemiological studies have suggested that, you know, adults on average will sleep for seven to nine hours. And but of course, you have people, you know, in the extreme portion. So people who

might sleep less than that, and people who might sleep more than that, there are people who might just make the choice, for example, of sleeping less, you know, they're curtailing their sleep because of external factors, because because they want to stay later. Because there's lots of things going on in life and it's hard to sometimes get that sleep, right? Or sometimes it's work or school schedules or family responsibilities. So sometimes we have different levels of control over that. So that's one group. There's people who actually get in bed for a decent period of time but can't sleep.

Like, for example, people who might suffer from insomnia. But there's also people who actually sleep less just because they need less sleep. So we know that sleep duration is partly determined by genetic factors. So I guess the key message here is that we should really listen to our own body and need and not feel guilty if we need a bit more sleep. I think a lot of people, honestly, might be listening to this and saying, you know, I'd love to get seven to nine hours of sleep. I hear this research that it's important, but, you know, my life is busy.

I just can't get that amount of sleep every night. I guess, what would you say to someone in that situation? You know, there's so many evidence now that sleep is a clear pillar for health. So I guess it's, you know, in terms of prioritizing, we hear a lot about, you know, in terms of prioritizing, we hear a lot about, you know, people trying to eat healthy, and do some exercise and stay active and all of that. But, you know, at the end of the day, sleep is also a critical part of health. If we just take

that example, we know that if you're exercising, you know, having being sleep deprived will lower the impact of your exercise on, you know, how you're building your muscles, how you're kind of working out your cardiovascular system and whatnot. And so really, you know, sleep is a very strong ally for health. Yeah. I'd like to see if we can focus in on cognition now, too, because there's there's there's a relationship between sleep and cognition that I want to talk about. I guess really just broadly speaking to start, how does sleep impact our cognitive functions? There's so many ways that it does. I guess, you know, there's a lot of evidence now. And I guess it kind of makes sense. We've all had a bad night. We've all, you know, tried to cope the next day after an all nighter or, you know, a poor night of sleep. And then it gets difficult to concentrate. It gets

difficult to kind of pay attention. We tend to go in loops as well. So our ability to kind of think creatively and, you know, come up with decent solutions is kind of altered. So there's actually a brain cleaning process that takes place during sleep. So during wake, well, you know, the more time we spend awake and the more we kind of focus and concentrate and learn new things, our brain is accumulating a lot of kind of metabolic waste, if you want, and neurotoxins. And, you know, during sleep, we know that the space between brain cells actually expands, especially during deep sleep. And that enables the liquid that's inside our brain to increase its flow and literally flush out those neurotoxins. There's hypothesis as well, if we focus, for example, on memory, that the more you form new memories as you're awake, you're forming new connections between brain cells. We're actually doing some pruning, if you want. We're kind of looking at what connections were the most important based on what we've learned on the day before.

And we're strengthening these connections and we're toning down the other connections that might be kind of more peripheral and less important. allocating resources to promote, you know, the most important aspects of what we should have retained from what we've gone through during wake. We'll be back in a moment. There's so much going on, it sounds like, when we're sleeping. So this is why it sounds like it's so important. Maybe we can just kind of look at, you know, what happens when we don't get that kind of sleep then. Like, you know, for example, most of us spend our days at work. So I guess what kind of effect does a lack of sleep have on our performance at work?

How might we see that manifest maybe? Yeah, so a little bit like we were discussing earlier, you know, there's the effects on attention, on concentration, on, you know, problem solving. Oftentimes, we'll get a little bit irritable or moody as well when we're getting sleep deprived. And so that's not so surprising as well to see then that we're seeing some mistakes and sometimes avoidable mistakes that have been made historically. If you look at, you know, plane crashes, train crashes, or, you know, spillage that had, you know, major environmental impacts, a lot of these historical events were kind of anchored in situations where

people had been working for very long periods of time. So being, you know, partially sleep deprived. And oftentimes, they'll happen at, you know, the early hours of the morning, at a time where our circadian clock, our biological clock is, you know, kind of really sending the body and brain that this should be sleep time. I've heard it kind of said there, you know, there's similar things to like, when you consume alcohol, the way that that affects your cognition. Can we talk about that? Is there kind of a comparison here to sleep deprivation? Yeah, unfortunately. So we talk quite a lot about drunk driving as we should. But I guess, you know, there's more and more awareness of the impacts of sleep deprivation on driving as well. There's studies that estimate that being awake for more than 18 hours straight is the same of having a blood alcohol content of 0.05%.

And if you do a full on sleep deprivation, like a full 24 hour period that you're not sleeping, then it's equivalent to having a 0.1, 0.10% blood alcohol content. Well, yeah, because we, you know, we think about, you know, we're not going to get behind the wheel after we've had some drinks, but we don't really think about, you know, I didn't have a good night sleep or a couple of good nights sleep not to get behind the wheel. But it sounds like that is something to consider. Yeah, absolutely. And I guess, you know, one of the tricky part as well, when we're talking about, you know, how the brain is behaving in those sleep deprived state is that there's sometimes also a disconnect between our actual performance, like how we're kind of behaving and how we perceive that we're affected. So there's data to suggest that when we're sleep deprived, we might be able in many situations to kind of maintain a certain performance level. But for example, if I get you to do a task in a scanner after a normal night of sleep,

and I get you to do the same task in the scanner after a night of sleep deprivation, you might still be able to kind of pull it off and do the task correctly. But the brain power that it will require you to do that will be much more significant. So if we look at the, you know, the intensity of the activations and the scope, the regions that are activated as well. So that kind of, you know, in my view, is interesting as well as a warning that, yeah, we might be able to kind of really, you know, focus and mobilize all of our energy to do something, but that makes us also more at risk of a tiny mistake that could be fatal. I also want to ask you about mental health. How does not having enough sleep affect our mood and

also our mental health? Yeah, that's an interesting one. And that's actually the core of my own research program. So it's pretty clear now that there's a bidirectional relationship between sleep and mental health. So it goes both ways, essentially, is what you're saying? feel so well from a mental health perspective, then it's also harder to sleep well. And we know that when you don't sleep well, it's harder to, you know, get better as well. So that kind of creates in a way a bit of a vicious cycle whereby, you know, you kind of feel depressed or really anxious. And then, you know, you're sleeping less because of that. But then you're also feeling more depressed and more anxious, and you have less resources to be able to cope with this because you don't sleep as much. But we know as well that, for example, when you're trying to go to sleep in the evening,

and when you're waking up maybe in the middle of the night as well, a lot of, you know, the brain wiring change at multiple levels. So for example, we have, if I might try to come up with a simplified story, we have the frontal part of the brain that's, you know, kind of the rational part of the brain that helps us kind of make sense of things and rationalize and, you know, and then we have the amygdala, for example, part of the limbic system, which is really involved in kind of the stress response, like the emotion regulation and all of that. And so during the evening and the nighttime, our frontal lobes or the rational part of the brain tends to shut down, tends to kind of go to sleep if you want. Whereas our amygdala stays pretty

active. And we know that the amygdala stays pretty active. And we know that, you know, the amygdala and the frontal lobe are in close connections to each other. So we know that, you know, for example, during the daytime, your amygdala might get fired up because you're stressed about something, but then your frontal lobe, almost like a reassuring parent will come in and say, no, no, that's okay. We've been there before, you know, we can handle this, just do this or that type of behavior. But at night, if your frontal lobe is sleeping, then the other side can kind of take over and you can start worrying a little bit more. Exactly. So I often say, you know, the nighttime

is the worst time ever to try to troubleshoot for most people, because your brain is just not wired for that. Your brain is wired for like freaking out because of things that you're not able to make sense. And oftentimes, you know, people might have had those experiences where, you know, it's 3am, you're kind of waking up, you're thinking about something that just kind of goes around and around in your head. And it kind of really stresses you out. And the next morning, you realize that you were thinking about something completely silly. That's really a non-issue. But, you know, the rational part of your brain has come back and said, yeah, don't worry about this. It's OK. We got it. Exactly. Exactly. So, you know, and that kind of explains why as well,

you know, we have that tendency on days where we might be a bit more stressed and then, you know, you're kind of going to bed it's it's kind of prime time for the little hamster to start running in the back of your head and then keeping you awake so i guess it's it's helpful for many people to just kind of understand that there's physiological reasons for that as well so you know the clever thing to do is just to realize that acknowledge it okay this is normal that's just my amygdala who's freaking out a little bit. Let's just kind of put that on the bedside table. Like I'm not going to resolve that problem right now. It's going to wait for me like next morning when I wake up.

Yeah. All right. And just to end here, Dr. Robillard, I want to get some advice from you really on sleep and sleep habits. So, I mean, what are some evidence based tips that that people can use for getting a good night's sleep? In terms of general tip for protecting sleep in, in everyone, I guess we can, we can try to leverage light to our advantage. So basically getting ourselves exposed to bright light in the morning, ideally kind of going outdoors and getting a lot of that natural sunlight that unfortunately nowadays, like a lot of us are kind of stuck indoors and living those types of life. The downside of that is that, you know, light in the evening can actually suppress our sleep hormones. So, you know, we want to kind of try to minimize light

in the evening. And I'm mentioning that because a lot of the devices that we're using now, if you think of your iPhone, iPads, your smartphones and screens, or the TV, those are all mini lamps, if you want to, those are all, you know, showing light and getting us exposed to light, especially light with a blue hue, which we know that the circadian system is especially sensitive to. Another tip that can be quite helpful is keeping regular bed and wake times. So really kind of keeping a strict kind of sleep schedule. And we often, like a lot of us, will have to use alarms for the morning.

One of the tricks that we can use also is using an alarm for bedtime in the evenings. So that could be another helpful trick. There's quite a lot of research as well now showing that exercise can help promote sleep. I guess the critical part is that we want to try to avoid, you know, close to bedtime, because if you exercise, you know exercise within the last hour before bedtime, then you might get your heart pumping, you might get your temperature rising, and all of these things are not conducive to sleep. So it can actually be hurtful, but exercise in the daytime. Exercise a bit earlier, yeah.

Yeah. Okay. And what if you're suffering though from insomnia? For some people who, from insomnia is called Cognitive Behavioral Therapy for Insomnia, or CBTI for short, doesn't involve any sleeping pill. This is actually something that people should do before getting to the sleeping pills and or sometimes at the same time, and kind of involves, you know, learning about sleep. We believe that knowledge is power. So, you know, the more people understand what is going on, the more they might be able to kind of circumvent some of these unhelpful thoughts and unhelpful behavior that we naturally tend to kind of put forward when we have issues sleeping. And that actually contribute to the chronicity of insomnia.

If people are interested to learn more in terms of what they can do to protect their sleep, they can reach out to us at researchsleep.ca. Dr. Robillard, this was fascinating. Thank you so much for speaking with me today. My pleasure. And I hope you sleep well tonight. Thank you, you too. That's it for today. I'm Maina Karaman-Wilms. Our intern is Manjot Singh. Our producers are Madeline White, Cheryl Sutherland,

and Rachel Levy-McLaughlin. David Crosby edits the show. Adrian Chung is our senior producer, and Angela Pachenza is our executive editor. Thanks so much for listening, and I'll talk to you next week.