Combo of Insufficient Sleep, Physical Activity Tied to Mortality Risks

By Lisa Rapaport

July 07, 2021

(Reuters Health) - Sedentary people who also sleep poorly have a significantly higher risk of all-cause, cardiovascular disease and cancer mortality than those with just one of these risk factors or neither, a UK study suggests.

Researchers examined data on 380,055 participants (mean age 55.9 years) in the UK Biobank study who had baseline data on moderate to vigorous physical activity (MVPA) as well as composite sleep scores based on chronotype, sleep duration, insomnia, snoring, and daytime sleepiness. Researchers created 12 different categories of combined physical activity and sleep from this data, ranging from one extreme of poor sleep and no MVPA to the other extreme of healthy sleep and high levels of MVPA.

At baseline, none of the participants had a history of cardiovascular disease or cancer. After an average follow-up period of 11.1 years, there were a total of 15,503 deaths from all causes, including 4,095 fatalities from cardiovascular disease and 9,064 from cancer.

Compared the healthiest extreme - healthy sleep and the highest MVPA - individuals with poor sleep and no MVPA were significantly more likely to die from all causes (hazard ratio 1.57), cardiovascular disease (HR 1.67), and cancer (HR 1.45).

"We found that physical inactivity amplified the health risks of poor sleep in a synergistic way, this means that the combined mortality risk from physical inactivity and poor sleep was larger than the sum of the independent risks of poor sleep alone plus physical inactivity alone," said senior study author Emmanuel Stamatakis, a professor of physical activity, lifestyle and population health at the University of Sydney in Australia.

"This is not surprising considering that poor sleep and physical inactivity work on similar cardiovascular and metabolic pathways," Stamatakis said by email. "For example, we know that both short sleep and physical inactivity cause metabolic and endocrine dysfunction, increase systemic inflammation, and cause stimulation of the sympathetic nervous system."

Participants' activity levels were sorted into four categories based on World Health Organization exercise guidelines using Metabolic Equivalent of Task (MET) minutes: no MVPA, low MVPA (1 to less than 600 MET minutes/week), medium MVPA (600 to 1,199), or high MVPA (1200 or more).

Overall, 223,445 (59%) participants were in the high-MVPA group; while 57,771 (15%) were in the medium group; 39,298 (10%) were in the low group; and 59,541 (16%) were in the no-MVPA group.

In addition, researchers scored participants' sleep quality from 0 to 5 based on chronotype, sleep duration, insomnia, snoring, and daytime sleepiness, and created three sleep quality categories: poor (scores of 0 to 1), intermediate (2 to 3), and healthy (4 or higher).

The majority of participants (56%) had a healthy sleep pattern, while 42% had intermediate sleep quality, and 3% were poor sleepers.

One limitation of the study is that sleep and MVPA data was self-reported and not independently verified, the study team notes in the British Journal of Sports Medicine. The sleep and MVPA data also was only collected at a single point in time.

In addition, said Jose Ordovas of the Human Nutrition Research Center on Aging at Tufts University in Boston, sleep quality is as important or even more important than quantity when it comes to sleep, and that was not measured in the study.

"Despite all the caveats, the study results apparently make sense: if one is sedentary and with poor sleep, the mortality/disease risk is high," Ordovas, who wasn't involved in the study, said by email.

The results also suggest that it makes sense for clinicians to recommend exercise for poor sleepers, said Jaana Halonen, research program director at the Finnish Institute for Health and Welfare in Kuopio.

"If a person has both poor sleep and he/she is inactive he/she may accumulate several different risk factors and thus have a more pronounced mortality risk," Halonen, who wasn't involved in the study, said by email. "Physical activity, on the other hand, may help to control weight, cholesterol, and blood pressure, and thus protect against harmful health effects."

SOURCE: British Journal of Sports Medicine, online June 29, 2021.