It’s a perennial dilemma when the alarm blares after a late night: Do you sacrifice an hour of rest to drag your body through a bleary workout? Or are you better off skipping the jog and sleeping in?
In an ideal world, experts say, you would get both ample exercise and ample sleep. But a new study suggests that exercise could potentially help counteract the health consequences of not getting a proper amount of sleep.
The new research builds upon a large body of work showing just how critical both sleep and fitness are for overall health. Various studies show that healthy amounts of each individually are linked to increased longevity. And at least one suggested that sleep problems tended to increase the chances a subject would die during the follow-up period but that regular exercise helped eliminate that risk.
A team of researchers based in China wanted to better understand the protective power of exercise, so it examined data collected in the United Kingdom from over 92,000 adults between the ages of 40 and 73. Participants spent a week between 2013 and 2015 wearing a wristband that measured how much they exercised and slept, which the researchers used as an indication of their lifestyle habits.
The researchers then tracked the health outcomes of the participants years later. Predictably, those who got paltry sleep, or those who slept too much (which in itself can also be problematic) and hardly exercised, were generally more likely to die during that period, including from issues such as cancer and cardiovascular disease. But the researchers also uncovered a surprising trend in the data: People who exercised a lot did not have an increased risk of death, even when they only slept less than six hours each night.
The study suggests that completing 150 minutes of moderate or vigorous physical activity every week might negate some of the health consequences associated with sleeping too much or too little, said Jihui Zhang, the director of the Center for Sleep and Circadian Medicine at the Affiliated Brain Hospital of Guangzhou Medical University and an author of the study. “Doing something is better than doing nothing,” he said. For example, regular short walks or rides on a stationary bike could pay off.
The study was observational and was not proof that exercise definitively counteracts the toll of unhealthy sleep. And, of course, one week of sleep and exercise data may not reflect people’s habits over their entire lives. But the findings present another intriguing window into the health benefits of exercise.
The researchers on the new study theorized that working out might help balance out the effects of unhealthy sleep by combating inflammation or possibly helping to regulate metabolism and sympathetic nervous system activity, Dr. Zhang said. It’s also possible that poor sleep contributes to heart disease risk by elevating blood pressure and inhibiting insulin resistance, said Dr. Virend Somers, a cardiologist who studies the effect of sleep loss at the Mayo Clinic. Exercise might counter this by regulating blood pressure and increasing insulin sensitivity.
One of the more compelling ways exercise interplays with sleep is in the brain, said Jennifer Heisz, an associate professor at McMaster University and author of “Move the Body, Heal the Mind.” That’s partly because a hard workout prods our cells to produce a chemical called adenosine, which functions as a natural sleep aid. The more adenosine we generate throughout the day, the more restful and restorative our sleep becomes — which could help counteract a night or two of patchy rest, she said.
Still, that doesn’t mean that people should sacrifice rest in order to exercise, said Tianyi Huang, an assistant professor of medicine at Harvard Medical School who has studied sleep and heart health. People who can’t get sufficient sleep are unlikely to have the energy to stay active during the day, he said, especially if their lack of sleep stems from a hectic work schedule. (If you struggle to sleep for prolonged periods of time, you may want to consult a doctor or sleep specialist.) Past research has also shown that morning workouts may influence your body differently than evening ones.
“What this tells us is that if you can’t manage your sleep optimally right now, we should be scheduling time to get moderate or vigorous physical activity,” said Dr. Donald Lloyd-Jones, a former president of the American Heart Association and the chair of the department of preventive medicine at Northwestern University’s Feinberg School of Medicine.
And not everyone has the same need for sleep, which means that some people can function well or feel sufficiently rested with fewer hours, Dr. Somers said. It’s possible that some of the “short sleepers” in the study were already rested and thus more able to add in a workout without increased cardiovascular risk, he said, rather than exercise somehow making up for their lack of rest.
When people are sleep-deprived, they may be more likely to injure themselves during a workout, said Aric Prather, a psychologist and sleep specialist at the University of California, San Francisco. The question shouldn’t be whether to trade sleep for exercise. “People who do best are people that do both well,” he said.
