Study: Regular Exercise May Protect Against Side Effects of Poor Sleep

Not getting enough sleep can prompt a variety of health consequences, but a new study found that high-intensity workouts could combat some of those negative side effects.

Both proper sleep and adequate exercise are seen to help prevent more than 80% of cardiovascular events, including heart attack, abnormal heart rhythms, and coronary artery disease. But obtaining sustainable habits in both these areas can be tricky for many individuals. While exercise may be more within individuals' control—you can choose to go for a run and then do it—sleep can be sought after but more complicated to nail down.

The good news is, maintaining those exercise habits while striving toward better sleep still provides positive benefits.

According to one of the study’s co-authors, Jihui Zhang, PhD, director of the Center for Sleep and Circadian Medicine at the Affiliated Brain Hospital of Guangzhou Medical University, in China, this may be due to the effect exercise has on inflammation, metabolism, and the sympathetic nervous system, all which are closely linked to heart health. 

“Therefore, to some extent, people should sacrifice rest for exercise if they have to choose one,” he said.

Exercise Provides Whole-Body Effects

In order to understand the role exercise plays in counteracting the side effects of poor sleep, researchers used data collected from more than 92,000 adults in the United Kingdom between 2013 and 2015. Their ages ranged from 40 to 73 years and 56% were female. For one week, they wore a wristband that measured how much they exercised and slept.

They broke nightly sleep into three categories: short (six hours or less), normal (six to eight hours), and long (more than eight hours). Based on World Health Organization (WHO) guidelines, they divided the amount of physical activity a person got into low, intermediate, and high. The research team also kept track of exercise intensity, and whether or not it was considered “moderate to vigorous” based on WHO guidelines. 

The study used death records to determine that after a median of about seven years after the data was collected, just over 3,000 participants died, about 1,100 from cardiovascular disease and about 1,900 from cancer.

Those who slept too much or not enough, and also did not get enough exercise—less than the recommended 150 minutes a week—were more likely to die from any cause, including cancer and heart disease.

In those who didn’t get enough sleep, exercising more than the minimum recommended amount appeared to make up for the loss of sleep. People who exercised more than 150 minutes per week did not have an increased risk of dying, even if they slept for less than six hours each night.

This was not the case for people who got intermediate amounts of exercise. In these people, not getting enough sleep raised their likelihood of all-cause death by about 40%.

The new research was observational, meaning it cannot confirm exercise can moderate some of the effects of loss of sleep, but Dr. Zhang and team emphasize exercise’s ability to fight inflammation, metabolic dysregulation, and sympathetic nervous system activity.

Exercise and Inflammation

According to an earlier study, muscle contractions during exercise release exerkines—molecules that can reduce inflammation associated with chronic disease, including heart disease and diabetes.

Inflammation in the cardiovascular system can affect blood flow to the heart and the tissues surrounding the organ. This can lead to serious health problems including arrhythmia—irregular heartbeat—and heart failure, which means that your heart can’t pump enough oxygen-rich blood to meet your body’s needs, and narrowing of the arteries.

Exercise works to counter inflammation; it also regulates cholesterol, excess fat, and high blood sugar, all of which contribute to heart disease. It also stimulates the sympathetic nervous system, which impacts heart rate and the heart’s ability to pump with the correct force.

How Much Exercise Is Too Much?

Although the new study did not specifically research whether or not too much exercise can have health consequences related to heart disease, cancer, and overall mortality, past research has suggested too much exercise and not enough rest can increase harmful inflammation. 

One 2019 study found that getting an adequate amount of exercise reduces inflammation, but too much can cause active muscles to trigger immune cells to release inflammatory mediators—a host of blood cells, proteins, and other important mediators that use inflammation to fight off intruders such as bacteria and viruses. The research found that intense, long exercise can lead to higher levels of inflammatory mediators and therefore chronic inflammation.

According to Bo-Huei Huang, PhD, an epidemiologist and biostatistician at the University of Technology Sydney in Australia, who studies the intersection of fitness and sleep, the amount and intensity of exercise each person needs will depend on a number of factors including age, whether someone is pregnant or has a chronic disease or disability. The same goes for sleep—some people need more than others. 

The findings also may not transfer to younger people, who typically need more sleep than older adults, noted Tamanna Singh, MD, co-director of the Sports Cardiology Center at Cleveland Clinic. 

“All this data is still so new, I think there’s a lot more to it than what we already know,” she explained.

Studies like this, which compare two aspects of health that are both important, should trigger people to become more intentional about their habits.

“If you’re not already moving, now is a good time to add intentional movement to your daily list of things that are important to you,” Dr. Singh suggested, acknowledging that different factors, including work, can make this easier for some than others.

So, How Important Is Sleep?

Huang emphasized that the importance of sleep cannot be overlooked. In 2022, the American Heart Association (AHA) added sleep to its list of eight crucial lifestyle factors for heart health, noting that adults should aim for 7-9 hours a night. 

If exercise replaces restful sedentary behaviors that aren’t sleep, say, sitting on the couch watching TV, the outcome will almost certainly be a positive one for a person’s health, reiterated Dr. Huang. But not getting enough sleep and expecting to erase the effects of that with exercise likely won’t be good for health in the long-term.

“When we think of overall cardiovascular fitness, it’s not that one thing is more important than the other,” Dr. Singh agreed. “It’s all about balance.”