Bedtime, sleep duration, and sleep quality and all-cause mortality in middle-aged and older Chinese adults: The Dongfeng-Tongji cohort study

Abstract

Objective: This study aims to investigate the associations of bedtime and its combination with sleep duration and sleep quality with all-cause mortality.

Methods: We conducted a prospective cohort study using data collected from 2008 to 2018 in the Dongfeng-Tongji cohort. Among 40,097 participants aged 62.1 on average at baseline, we applied Cox regression models to assess hazard ratios and 95% confidence intervals for mortality risk.

Results: During a mean follow-up of 8.2years, 4345 deaths were documented. U-shaped associations of bedtime and sleep duration with all-cause mortality were observed. Compared with bedtime between 10:01 PM and 11:00 PM, the hazard ratio (95% confidence interval) for all-cause mortality was 1.34 (1.20-1.49) for ≤9:00 PM, 1.18 (1.09-1.27) for 9:01-10:00 PM, and 1.50 (1.13-2.00) for >12:00 AM, respectively. Participants with sleep duration of <6, 6-<7, 8-<9, and ≥9 h/night had a respective 39%, 21%, 11%, and 25% higher all-cause mortality risk than those sleeping 7-<8 h/night. Additionally, participants with a healthy sleep score of 3, characterized as proper bedtime (10:01 PM-12:00 AM), moderate sleep duration (7-<8h/night), and good/fair sleep quality, had a significantly 36% (hazard ratio, 0.64; 95% confidence interval, 0.56-0.74) lower all-cause mortality risk than those with a score of 0.

Conclusions: Individuals with early or late bedtimes and short or long sleep duration were at higher all-cause mortality risks. Having healthy sleep habits may significantly reduce death risk.

Keywords: All-cause mortality; Bedtime; Joint association; Prospective cohort study; Sleep duration; Sleep quality.