Sleep lengthening in late adulthood signals increased risk of mortality.

Study Objectives: Epidemiological evidence indicates that both short and long sleep at midlife increase mortality risk, but few studies have examined how change in sleep duration between midlife and later life affects this risk. We examined the association between change in sleep duration and mortality risk.

Methods: The Singapore Chinese Health Study is a prospective cohort of 63257 Chinese in Singapore aged 45-74 years at recruitment (1993-1998). Self-reported sleep duration was collected from 39523 participants who completed both baseline (mean age 54.8 years) and follow-up II (mean age 67.9 years; 2006-2010) interviews, which were on average 12.7 years apart. Mortality data were obtained via linkage with national death registry up to December 31, 2015.

Results: Compared with participants who reported sleeping the recommended duration (7 hr) at both interviews, those with persistently short sleep (≤5 hr) had increased risk of all-cause mortality (hazard ratio [HR] 1.27, 95% confidence interval [CI] 1.06-1.53). Similarly, those with persistently long sleep (≥9 hr) had increased risk of all-cause (HR 1.47, 95% CI 1.24-1.73) and cardiovascular (HR 1.40, 95% CI 1.04-1.89) mortality. The proportion of long-sleepers increased with aging (6%-23.7%). Progression to long sleep from short (HR 1.50, 95% CI 1.24-1.81) or recommended (HR 1.43, 95% CI 1.25-1.64) duration was associated with increased all-cause mortality, especially for cardiovascular mortality. Change in sleep duration was not linked to cancer mortality.

Conclusions: Persistent short or long sleep or increasing sleep duration in late adulthood was associated with increased risk of all-cause mortality, especially from cardiovascular causes.