Associations of sleep characteristics with all-cause, cardiovascular and non-cardiovascular mortality among rural Chinese older adults: a cohort study.

Study Objectives: The longitudinal associations of sleep timing and time in bed (TIB) with all-cause, cardiovascular and non-cardiovascular mortality are unclear in Chinese rural populations.

Methods: This population-based cohort study included 2468 participants who were aged ≥60 years and residing in rural communities in western Shandong Province. Sleep timing and TIB were assessed using standard questionnaires at baseline in 2014. Mid-sleep time was defined as the halfway point between the bedtime and wake-up time. Vital status until December 2022 and causes of death for all participants were ascertained via death registry plus interviews with informants (eg, family members or village doctors). Data were analysed using restricted cubic splines (RCS) and Cox proportional-hazards models.

Results: During the mean follow-up of 7.36 (SD 2.03) years, 657 participants died. The RCS analysis showed non-linear relationships of sleep duration and mid-sleep time at baseline with all-cause and cardiovascular mortality. Specifically, when baseline sleep characteristics were categorised into tertiles, the multivariable-adjusted HR for all-cause mortality was higher for long sleep duration (>8 vs 7-8 hours; HR 1.27; 95% CI 1.06 to 1.53), long TIB (>9 vs <8 hours; 1.63; 1.27 to 2.08), early bedtime (before 21:00 vs 22:00 or later; 1.58; 1.00 to 2.49) and early mid-sleep time (before 01:00 vs 01:00 -01:30; 1.45; 1.20 to 1.76). Long TIB was associated with a multivariable-adjusted HR of 1.61 (1.15 to 2.27) for cardiovascular mortality and 1.64 (1.09 to 2.47) for non-cardiovascular mortality.

Conclusions: Long sleep duration and early sleep timing might be associated with increased risk of all-cause and cardiovascular mortality in rural Chinese older adults. In addition, long TIB might be linked to an increased risk of all-cause, cardiovascular and non-cardiovascular mortality.