Association of postlunch napping duration and night-time sleep duration with cognitive impairment in Chinese elderly: A cross-sectional study

Abstract

Objective To analyse the independent and combined associations of postlunch napping duration and night-time sleep duration with risk of cognitive impairment among Chinese elderly Design A cross-sectional study Setting We analysed the data from Zhejiang Ageing and Health Cohort, a population-based survey of seven counties located in Zhejiang province in eastern China Participants 10 740 participants aged 60 years or older were included in final analysis Primary and secondary outcome measures Cognitive impairment was assessed through Mini-Mental State Examination Data on sleep-related characteristics was collected in the behavioural habits section within the questionnaire Results Relative to participants with 1-30 min of postlunch napping, those who did not nap and who napped longer had significantly higher risks for cognitive impairment OR of cognitive impairment were 141 (95% CI 114 to 175) for participants with longer night-time sleep duration (≥9 hours), compared with those sleeping 7-89 hours In addition, combined effects were further identified Participants with both longer night-time sleep duration (≥9 hours) and longer postlunch napping duration (>60 min) (OR=201, 95% CI 130 to 313), as well as those with both longer night-time sleep duration (≥9 hours) and appropriate postlunch napping duration (1-30 min) (OR=201, 95% CI 120 to 338), showed significantly higher risk of cognitive impairment than those with sleeping 7-8 hours and napping 1-30 min Meanwhile, a 34% increase in odds of cognitive impairment was observed in participants with both shorter night-time sleep duration (5-69 hours) and no napping Conclusion Both postlunch napping duration and night-time sleep duration were independently and jointly associated with cognitive impairment, which needs verification in prospective studies.