Sleep regularity is a stronger predictor of mortality risk than sleep duration

Abnormally short or long sleep durations have been associated with higher risks for premature mortality and achieving optimal sleep duration has been the focus for most sleep health guidelines. Emerging research has demonstrated that sleep regularity can be a stronger predictor for some health outcomes than sleep duration. The role of sleep regularity in mortality, however, has not been investigated prospectively in a large cohort with objective sleep data. We therefore aimed to compare how sleep regularity and duration predicted risk for all-cause mortality and cause-specific mortality in UK Biobank participants. We calculated Sleep Regularity Index (SRI) scores from >10 million hours of accelerometer data in 60,977 participants (62.8±7.8 years of age, 55.0% female, median [IQR] SRI: 81.0 [73.8-86.3]). Mortality events were reported up to 7.8 years after accelerometer recording in 1,859 participants. Higher sleep regularity was associated with a 23-48% lower risk of all-cause mortality, a 17-39% lower risk of cancer mortality, and a 27-57% lower risk of cardiometabolic mortality, across the top four SRI quintiles compared to the least regular quintile. Results were adjusted for age, sex, and ethnicity, and remained robust after additional adjustment for sociodemographic and lifestyle factors. Sleep regularity was a stronger predictor of all-cause mortality than sleep duration, based on a comparison of equivalent mortality models, and by comparing nested SRI-mortality models with and without sleep duration as a predictor. These findings indicate that sleep regularity is an important predictor for mortality risk and is a better predictor than sleep duration. As behaviorally improving sleep regularity is potentially more feasible than increasing sleep duration, sleep regularity may be a primary target for improving general health and survival.