Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study

Daniel P Windred, Angus C Burns, Jacqueline M Lane, Richa Saxena, Martin K Rutter, Sean W Cain, Andrew J K Phillips, Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study, Sleep, Volume 47, Issue 1, January 2024, zsad253, https://doi.org/10.1093/sleep/zsad253

Abnormally short and long sleep are associated with premature mortality, and achieving optimal sleep duration has been the focus of sleep health guidelines. Emerging research demonstrates that sleep regularity, the day-to-day consistency of sleep–wake timing, can be a stronger predictor for some health outcomes than sleep duration. The role of sleep regularity in mortality, however, has not been investigated in a large cohort with objective data. We therefore aimed to compare how sleep regularity and duration predicted risk for all-cause and cause-specific mortality. We calculated Sleep Regularity Index (SRI) scores from > 10 million hours of accelerometer data in 60 977 UK Biobank participants (62.8 ± 7.8 years, 55.0% female, median[IQR] SRI: 81.0[73.8–86.3]). Mortality was reported up to 7.8 years after accelerometer recording in 1859 participants (4.84 deaths per 1000 person-years, mean (±SD) follow-up of 6.30 ± 0.83 years). Higher sleep regularity was associated with a 20%–48% lower risk of all-cause mortality (p < .001 to p = 0.004), a 16%–39% lower risk of cancer mortality (p < 0.001 to p = 0.017), and a 22%–57% lower risk of cardiometabolic mortality (p < 0.001 to p = 0.048), across the top four SRI quintiles compared to the least regular quintile. Results were adjusted for age, sex, ethnicity, and sociodemographic, lifestyle, and health factors. Sleep regularity was a stronger predictor of all-cause mortality than sleep duration, by comparing equivalent mortality models, and by comparing nested SRI-mortality models with and without sleep duration (p = 0.14–0.20). These findings indicate that sleep regularity is an important predictor of mortality risk and is a stronger predictor than sleep duration. Sleep regularity may be a simple, effective target for improving general health and survival.

Sleep of adequate duration is important for optimal health and longevity, but emerging evidence demonstrates that regular sleep timing may be even more important. Using objective measures of sleep in a cohort of > 60 000 individuals, we found that people with less regular sleep patterns have a higher risk of premature mortality, and that sleep regularity is a stronger predictor of mortality risk than sleep duration. These findings were robust with detailed control for confounding factors, providing evidence that sleep regularity is a key index of human health and potentially a more important marker of health than sleep duration.

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