Sleep timing and the prevalence of hypertension in middle-aged and older populations: the sleep heart health study.

Objectives: Sleep characteristics such as duration, continuity, and irregularity are associated with the risk of hypertension. This study aimed to investigate the association between sleep timing (including bedtime, wake-up time, and sleep midpoint) and the prevalence of hypertension.

Methods: Participants were selected from the Sleep Heart Health Study (n = 5504). Bedtime and wake-up times were assessed using sleep habit questionnaires. The sleep midpoint was calculated as the halfway point between the bedtime and wake-up time. Restricted cubic splines and logistic regression analyses were performed to explore the association between sleep timing and hypertension.

Results: A significant nonlinear association was observed between bedtime (P_overall<0.001; P_nonlinear<0.001), wake-up time (P_overall=0.024; P_nonlinear=0.076), sleep midpoint (P_overall=0.002; P_nonlinear=0.005), and the prevalence of hypertension after adjusting for potential confounders. Multivariable logistic regression showed that both late (> 12:00_AM and 23:01_PM to 12:00_AM) and early (≤ 22:00_PM) bedtimes were associated with an increased risk of hypertension compared to bedtimes between 22:01_PM and 23:00_PM. In addition, individuals with late (> 7:00_AM) and early (≤ 5:00_AM) wake-up times had a higher prevalence of hypertension than those with wake-up times ranging between 5:01_AM and 6:00_AM. Delaying the sleep midpoint (> 3:00_AM) was also associated with an increased risk of hypertension. Furthermore, no significant interaction effect was found in the subgroup analyses stratified by age, sex, or apnea-hypopnea index.

Conclusions: Our findings identified a nonlinear association between sleep timing and hypertension. Individuals with both early and late sleep timing had a high prevalence of hypertension.