Can exercise counter the health problems caused by poor sleep quality?
Tegan Taylor: Here are two things you already know are good for you; exercise and sleep. But just how much of an effect do they have on your risk of dying, and is one more powerful or protectant than the other? A group of researchers has been looking into exactly this, focusing on how sleep and physical activity interact with your risk of dying from cancer and cardiovascular disease. The top-line result is that they are both protective, and if you can only get one, exercise might be better. But let's drill down into the results with a bit more nuance with one of the authors, Emmanuel Stamatakis from the Charles Perkins Centre at the University of Sydney. Welcome Emmanuel.
Emmanuel Stamatakis: Thanks for having me, Tegan.
Tegan Taylor: So we already know that sleep and exercise are good for us, so what's new in this study?
Emmanuel Stamatakis: There is a number…we found a number of novel results, the most important one is that if you put the physical inactivity, not doing enough physical activity and having a poor sleep pattern into the same basket, what you get is a risk that is larger than the sum of the individual risks. So, in other words, we found what we call a synergy between those two established, as you pointed out, behavioural risk factors.
Tegan Taylor: That's right, and it went in both directions, so if you got both you were better, and if you didn't get either, you were worse.
Emmanuel Stamatakis: Much worse. So specifically we found…the jargon is multiplicative interaction, which is very simple, it simply means that if you have, let's say, 20% increase in risk from physical activity and 30% increase from poor sleep, for people who have both of them, you don't get the sum, you get more than the sum, you get the product, you get the product, you get 60% high risk.
Tegan Taylor: So I think a lot of us would think of sleep and physical activity as things we can either choose to do or choose not to do, but there is actually a lot in here that we can't choose, especially around the sleep space. You looked at…healthy sleep was sort of a combination of things like whether or not you were an early-bird or a night-owl, how long you slept for, whether you had insomnia, whether you snored, whether you were sleeping in the daytime. Really the only thing there that you can kind of control for yourself is how long you sleep for. So how do you act on this if you are just an individual?
Emmanuel Stamatakis: This is the subject of an ongoing discussion in various scientific disciplines and subdisciplines, including epidemiology where I work, because strictly speaking it's debatable whether sleep is a behaviour, and therefore the expression 'sleep hygiene' is not always correct, exactly because the sleep is to a large extent beyond our control, so therefore behaviour implies that we have some reasonable control over it. The only aspect of sleep is sleep duration, because nobody chooses to have insomnia, for example, nobody chooses whether they snore or not, nobody chooses whether they have daytime sleepiness.
The good news, and that's the second major finding that came out from our study, is that physical activity at levels equivalent to meeting the Australian Department of Health or WHO 2020 recommendations, seems to counteract most, if not all of the risks of poor sleep, long-term risks of poor sleep.
So our study essentially…the message is a very positive one, it's a very positive and a very optimistic message because although sleep is to a large extent beyond your control, there is something we can do to counter the health risks of sleep, so that's one level of optimism, you could say, that our study provides.
The second level of optimism is that previous research of ours has shown that physical activity increases the chances of people getting a good night's sleep, and a good night's sleep increases the chances of people becoming physically active in the future. So there seems to be a fair amount of behavioural interaction between the two variables because I'll just say that perhaps sleep should not be called a health behaviour, between the two variables there is a certain amount of behavioural interaction which makes physical activity a win-win all-round intervention, a win-win all-round option for people who experience sleep problems. Sleep problems are not a niche problem, it's about 40% of Australian adults at any given time suffer from at least one form of sleep disturbance. 60% of us would experience sleep disturbances at some point and 15% of Australians could be clinically classified as suffering from insomnia.
Tegan Taylor: Right, so it really affects a lot of people. And you said before the WHO physical activity guidelines and of course that's looking for at least 150 minutes of moderate intensity exercise a week or 75 minutes a week of vigorous intensity exercise. So you were looking at specifically cancer and cardiovascular disease risk of death. Why did you focus on those?
Emmanuel Stamatakis: We chose the outcomes based on previous literature, previous sleep epidemiology literature, and we chose our outcomes were all-cause mortality, cardiovascular mortality, cancer mortality, and we also looked at some subtypes of cardiovascular disease. And cancer mortality specifically we looked at lung cancer mortality and stroke and coronary heart disease. Yes, our decision was driven by previous sleep literature which showed that these are the kind of cardiovascular and cancer outcomes that seem to be affected the most by poor sleep patterns.
Tegan Taylor: And so the main takeaway for people is get exercise if you can't get sleep?
Emmanuel Stamatakis: For the lay public, the main takeaway is that the physical activity, exercise, is a win-win all around because not only for those who experience sleep problems it will improve their sleep, basically help them solve the problems. Even if they don't solve the sleep problems through exercise, physical activity may decrease their long-term health risks of sleep.
And of course we should not forget that physical activity is linked with all sorts of benefits, mental health, physical health, cognition, cardiovascular, metabolic, diabetes, we could be talking here for another 20 minutes about the list of benefits. So yes, physical activity, the main take-home for people is that physical activity is a win-win all around and this is not only for laypeople, this is a message to be heard by healthcare professionals who deal with patients, the general public, like general practitioners or clinicians who are dealing with people who suffer from sleep problems.
Tegan Taylor: Let's hope they are listening to this right now. Thank you so much Emmanuel.
Emmanuel Stamatakis: Thanks very much.
Tegan Taylor: Emmanuel Stamatakis is a Professor of Physical Activity, Lifestyle and Population Health at the University of Sydney.
Here are two things you already know are good for you: exercise, and sleep.
But just how much of an effect do they have on your risk of dying? And is one more powerful a protectant than the other?
A group of researchers has been looking into exactly this, focusing on how sleep and physical activity interact with your risk of dying from cancer and cardiovascular disease.
Guest: Professor Emmanuel Stamatakis
Charles Perkins Centre at the University of Sydney
Host:
Tegan Taylor
Producer:
Sarah Sedghi
In this episode