Please keep in mind that this is, overall, a good news story. You just need to take in some unpleasant facts first.
A routine lack of sleep doesn’t just leave you with a foggy mind and a grumpy mood.
There’s plenty of evidence that poor sleep is associated with a heightened risk of cardiovascular disease, cancer and death.
It can also make you fat, because lack of sleep impairs the metabolism of blood sugar and reduces the number of calories burned.
All of which is grim news considering that a third of adult Australians have confessed to getting less than the minimum recommended amount of seven hours of sleep a night.
So there’s that.
Meanwhile, a lack of physical activity will also boost your chances of getting cancer or dying from a heart attack or stroke.
And guess what? According to the Australian Institute of Health and Welfare, more than half (55 per cent) of adults do not meet the physical activity guidelines.
“Both behaviours are critical for health but, sadly, our society suffers from both a physical inactivity and a poor sleep crisis,” said Professor Emmanuel Stamatakis, director of the Physical Activity, Lifestyle, and Population Health research program at Charles Perkins Centre, University of Sydney.
But here is the good news.
In a new study, Professor Stamatakis and colleagues wondered if fixing one problem might go some way in fixing the other?
As the authors explained in The Conversation: “We set out to answer the question: If I have poor sleep but I do quite a lot of physical activity, can that offset some of the harms of my poor sleep in the long term? Or would this not make any difference?”
Here’s how the study worked
The researchers analysed the sleep and exercise habits of 380,055 middle-aged adults in the UK Biobank study, recruited between 2006 and 2010.
Participants were grouped, based on their sleep behaviour, into healthy, intermediate or poor.
Participants’ level of physical activity was assessed against the World Health Organisation guidelines.
Those who did 300 minutes of moderate intensity physical activity a week, or 150 minutes of vigorous exercise, or a combination of both, were in the top tier.
Those who met the minimum requirements (150 minutes of moderate intensity exercise a week, or 75 minutes of vigorous exercise, or a combination) were in the second tier.
Those who did little to no exercise were in the bottom tier.
The follow-up, 11 years later
By May 2020, 15,503 participants had died: 4095 died from heart disease and 9064 died from cancer.
Working through the numbers, the researchers found that, compared to healthy sleepers, people with poor sleep had a 23 per cent higher risk of premature death, a 39 per cent higher risk of dying from heart disease, and a 13 per cent higher risk of dying from cancer.
They then compared the data of people who slept well with those who slept poorly, and how much they exercised.
“We found people who had the highest risk of dying from heart disease and cancer were those who had poor sleep and didn’t meet the WHO physical activity guidelines,” the study authors write.
“On the other hand, those who had poor sleep but did enough physical activity to meet the WHO guidelines didn’t have as high a risk of dying from heart disease or cancer, compared to those who slept poorly and didn’t meet the physical activity guidelines.”
Simply by meeting the bottom threshold of the WHO guidelines for exercise “could reduce or eliminate some of the health harms of poor sleep”.
“Considering that physical activity is perhaps more modifiable than sleep, our study offers people more health incentives to be physically active,” Professor Stamatakis said.
“[It] provides health professionals with more reasons to prescribe physical activity to patients with sleep problems.”