Association of bedtime with mortality and major cardiovascular events: an analysis of 112,198 individuals from 21 countries in the PURE study

DOI: https://doi.org/10.1016/j.sleep.2021.01.057

Commentary

This study was investigating the association between bedtime and mortality and major cardiovascular events.

Bedtime was recorded in the Prospective Urban Rural Epidemiology (PURE) based on self-reported bedtime routines of 112,198 participants from 21 countries.

They were followed up prospectively for 2 years.

The association between bedtime and the composite outcome of death from all causes, non-fatal myocardial infarction, stroke, and heart failure was examined. Participants whose usual bedtime was before 10 p.m. were classified as "early" sleepers, while those who reported a bedtime after midnight were classified as "late" sleepers. The Cox-Frail model was applied with random intercepts to account for clustering within centers.

As a result, a total of 5633 deaths and 5346 major cardiovascular events were reported. A U-shaped association between bedtime and the composite outcome was observed, with a higher risk of the composite outcome for both early and late sleepers after adjusting for age and gender, when those who went to bed between 10 pm and midnight were used as the reference group.

In a fully adjusted model that included demographic factors, lifestyle behaviors (including total sleep time), and medical history, the results were substantially attenuated, but the estimates were similar for the earlier (HR 1.09 [1.03-1.16]) and later sleepers (HR 1.10 [1.02 -1.20]).

The results of this analysis suggest that early (before 10 p.m.) and late (after midnight) bedtimes may be considered risk factors as indicators of adverse health effects.