Midday napping duration and risk of stroke: A prospective study in China.

Background: Evidence on the potential effects of midday napping on risk of stroke in Chinese populations remains limited.

Objectives: We aimed to prospectively investigate the association between midday napping and risk of subsequent stroke and stroke subtypes in the Kailuan study.

Methods: Midday napping duration was obtained from a self-reported questionnaire. Incident stroke cases from baseline (2014) to December 31, 2020 were confirmed by review of medical records. The association of midday napping duration with risk of incident stroke and subtypes was examined using a Cox regression model, adjusting for potential confounders. We further investigated the joint effects of nocturnal sleep duration and midday napping on the risk of stroke.

Results: A total of 96,899 individuals (21.0 % women; 51.9 ± 14.0 years) were included. During an average follow-up of 5.62 ± 0.69 years, 2539 incident stroke cases were documented. After adjusting for potential confounders, we found that participants with a midday napping duration of >60 min/day had higher risk of incident stroke (adjusted HR: 1.23; 95 % CI: 1.07, 1.42), compared with those without midday napping. Furthermore, significant joint effects were found in both nocturnal sleep duration (P-interaction=0.04) and snoring status (P-interaction= 0.005) on the association between midday napping duration and the risk of incident stroke, especially for participants who napped >60 min/day and slept ≤7 h/night compared with those who slept 7-8 h/night and did not take a nap, or those who napped >60 min/day and snored compared with those who did not take a nap and snore.

Conclusions: We found that prolonged midday napping (>60 min/day) was associated with higher risk of stroke and the association was stronger among those with shorter nocturnal sleep duration or those who snored.