Physical activity offsets downsides of abnormal sleep duration

Short and long sleep durations were tied to higher risks for all-cause, cardiovascular disease (CVD), and cancer mortality, but these may be attenuated by engaging in physical activity (PA), a population-based cohort study suggests.

“We reported several important findings,” said the researchers. “First, accelerometer-measured PA (total PA volume and time spent in moderate-to-vigorous PA [MVPA]) and sleep duration were independently associated with mortality in a curvilinear dose-response manner.”

In the adjusted multivariate Cox models, short sleepers had increased risk for all-cause and CVD mortality (hazard ratios [HRs], 1.34 and 1.56, respectively) vs normal sleepers. A higher PA volume reduced all-cause, CVD, and cancer mortality risks by nearly 50 percent compared with low PA volume. MVPA exceeding the WHO standard recommendation also decreased all-cause, CVD, and cancer mortality risks (HRs, 0.67, 0.61, and 0.73, respectively). [Eur J Prev Cardiol 2023;30:832-843]

“The most striking finding was that objectively measured PA and sleep duration had significant additive and multiplicative interactive effects on mortality risks,” they continued.

Joint associations

The risk for all-cause mortality was highest among short sleepers with low PA volume (HR, 2.51) followed by long sleepers with low PA volume (HR, 2.06; p<0.001 for both). A similar trend was seen for CVD mortality in the low-PA volume category (HRs, 3.93 and 2.35; p<0.001 for both).

Compared with normal sleepers who engaged in guideline-recommended MVPA, short and long sleepers who did not engage in the recommended MVPA had the greatest risk for all-cause (HRs, 1.88 and 1.69 for short and long sleep, respectively) and CVD mortality (HRs, 2.40 and 1.66; p<0.001 for all).

“More importantly, we found that engaging in MVPA well above the lower threshold recommended by the WHO seemed to be able to mitigate most detrimental associations of unusual sleep duration with mortality,” they said.

For cancer mortality, the highest risk was among long sleepers (HRs, 1.85 [low PA volume] and 1.57 [no recommended MVPA]; p<0.001 for both). The corresponding HR values for short sleepers were 1.83 and 1.49 (p<0.001 for both).

Population characteristics

A 7-day accelerometer recording was done on >90K participants (mean age 62.4 years, 56 percent female) from the UK Biobank between February 2013 and December 2015. About three-quarters of the cohort had normal sleep duration (6–8 hours), 20 percent were long sleepers (>8 hours), while 7 percent were short sleepers (<6 hours). Over a third of participants were physically inactive (ie, 33 percent had low PA volume, while 39 percent did not meet the MVPA recommended targets).

Short sleepers were usually younger, shift workers, and had inadequate MVPA. Moreover, quite a number of short sleepers were obese or had prevalent CVD and cancer. Conversely, long sleepers were typically older and had less amount of PA. But as with short sleepers, a fraction of long sleepers were obese or had more comorbidities.

There were 3,080 deaths over a median follow-up of 7 years. Of these, 1,074 were due to CVD while 1,871 were from cancer.

Targeting one behaviour may not be enough

Programmes targeting both time-dependent behaviours may be more effective in preventing or delaying premature death among middle-aged individuals than targeting only one, the researchers stressed.

They underscored that while it is vital to maintain a normal sleep duration, it may not be enough; amplifying it with guideline-recommended PA and sustaining both practices in the long term may yield greater benefits for maintaining longevity.

Should there be a need to adjust sleep duration, engaging in PA may compensate for these disruptions. “[G]etting sufficient exercise may partially offset the detrimental impact of missing a good night’s sleep,” said study investigator Dr Jihui Zhang from The Affiliated Brain Hospital of Guangzhou Medical University in China, in a press release.