Association between the self-reported duration and quality of sleep and cognitive function among middle-aged and older adults in China

Background: The World Alzheimer Report showed that 46.8 million people suffered from dementia in 2015. This study examined how the duration and quality of sleep are associated with cognition among older adults in China. Method: Data were drawn from waves 2011, 2013, and 2015 of the China Health and Retirement Longitudinal Study (CHARLS), including noninstitutionalized adults aged 45 and older (n=10,768). Cognition was measured by interview-based assessments of mental status (TICS-10), episodic memory, and visuospatial abilities. Sleep duration was categorized as long, medium, or short and sleep quality was categorized as good, fair, or poor. Results: Sleep duration had an inverted U-shape relationship with cognitive scores (P < .001); and sleep quality had a positive linear relationship with cognitive scores (P < .001). Short and long sleep durations were associated with consistently lower cognition scores with increasing age (both P < .001); and fair and poor quality of sleep were associated with consistently lower levels of cognition (both P < .001). Tests of interactions between sleep duration and sleep quality showed that participants reporting long durations of sleep with poor quality of sleep had the lowest overall cognitive scores. Limitations: Self-reported methods were used to measure sleep quality and duration and thus our findings underscore the need for more evidence-based research to improve prevention efforts and tailor interventions to reduce cognitive decline among Chinese older adults. Conclusions: Suboptimal sleep duration and quality were associated with poor cognition. Cognitive scores were lowest among those who reported long durations of sleep that were of poor quality.