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

Abstract

ObjectiveTo analyse the independent and combined associations of postlunch napping duration and night-time sleep duration with risk of cognitive impairment among Chinese elderly.DesignA cross-sectional study.SettingWe analysed the data from Zhejiang Ageing and Health Cohort, a population-based survey of seven counties located in Zhejiang province in eastern China.Participants10 740 participants aged 60 years or older were included in final analysis.Primary and secondary outcome measuresCognitive impairment was assessed through Mini-Mental State Examination. Data on sleep-related characteristics was collected in the behavioural habits section within the questionnaire.ResultsRelative 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 1.41 (95% CI 1.14 to 1.75) for participants with longer night-time sleep duration (≥9 hours), compared with those sleeping 7–8.9 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=2.01, 95% CI 1.30 to 3.13), as well as those with both longer night-time sleep duration (≥9 hours) and appropriate postlunch napping duration (1–30 min) (OR=2.01, 95% CI 1.20 to 3.38), 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 (5–6.9 hours) and no napping.ConclusionBoth postlunch napping duration and night-time sleep duration were independently and jointly associated with cognitive impairment, which needs verification in prospective studies.

Short Daytime Napping Reduces the Risk of Cognitive Decline in Community-Dwelling Elderly Individuals: a 5-Year Longitudinal Study

“…Lin et al [10] conducted a large-scale cross-sectional study in 10,740 Chinese older adults (≥60 years) and found that short nappers (<30 min) had a signi cantly lower prevalence of cognitive impairment as assessed by the MMSE compared to no nappers and long nappers (≥30 min). Our ndings are consistent with this report.…”

“…In a cross-sectional study in clinical settings, Asada et al [21] found that napping for up to 60 min, but not more than 60 min, was protective against the development of Alzheimer's disease. Lin et al [10] conducted a large-scale cross-sectional study in 10,740 Chinese older adults (≥60 years) and found that short nappers (<30 min) had a signi cantly lower prevalence of cognitive impairment as assessed by the MMSE compared to no nappers and long nappers (≥30 min). Our ndings are consistent with this report.…”

“…According to recent reviews and meta-analyses, sleep duration and sleep disturbance are determinants of cognitive decline and dementia [3][4][5][6][7]. Moreover, daytime napping is reportedly associated with cognitive function in older adults [8][9][10][11]. However, previous study ndings have been somewhat inconsistent; some reported possible adverse effects of napping, especially long napping, on cognitive function [9,11], whereas others reported possible bene cial effects of napping, especially short napping [8,10].…”

“…However, previous study ndings have been somewhat inconsistent; some reported possible adverse effects of napping, especially long napping, on cognitive function [9,11], whereas others reported possible bene cial effects of napping, especially short napping [8,10]. Furthermore, except for one longitudinal study [8], only cross-section studies [9][10][11] have been conducted. More longitudinal studies are awaited to accumulate evidence of higher levels.…”

“…Moreover, daytime napping is reportedly associated with cognitive function in older adults [8][9][10][11]. However, previous study ndings have been somewhat inconsistent; some reported possible adverse effects of napping, especially long napping, on cognitive function [9,11], whereas others reported possible bene cial effects of napping, especially short napping [8,10]. Furthermore, except for one longitudinal study [8], only cross-section studies [9][10][11] have been conducted.…”