Both Short and Long Sleep Durations Are Associated with Poor Cognition and Memory in Chinese Adults Aged 55+ Years—Results from China Health and Nutrition Survey

SIMPLE SUMMARY: Sleep plays an important role in cognition and memory in older adults and elderly populations. Rapid ageing in low-and middle-income countries (LMICs), including China, comes with the great challenge of the increased prevalence of cognition decline and dementia, consequently leading to an increase in chronic disease burdens. However, most studies that investigate the association between sleep and cognition are carried out in high-income countries and are limited to cross-sectional studies, whereas 80% of the world’s older population is estimated to live in LMICs in 2050. To fill in the gap, we aim to examine the associations between sleep duration and cognitive functions and memory in older Chinese adults in 2004, 2006, and 2015, using the China Health and Nutrition Survey. We found a U-shaped relationship between sleep duration, cognition, and memory, with a short and long sleep duration being associated with a 23% and 47% increase in cognitive decline and 63% and 48% increase in poor memory, respectively. These associations were not modified by demographic features such as education, income, and urbanity. These findings confirmed the importance of maintaining a normal sleep duration for cognition function. Our results may implicate the need for potential prevention strategies in reducing cognition decline and dementia in other LMIC populations. ABSTRACT: We aimed to examine the associations between sleep duration and cognitive functions and memory in older Chinese adults attending the China Health and Nutrition Survey. A total of 7924 participants 55 years and older who reported their sleep duration and had a cognitive screen test in 2004, 2006, and 2015 were included in the analysis. Mixed-effects logistic regression models were used to assess the associations. A short sleep duration (≤6 h/day) and long sleep duration (≥10 h/day) were positively associated with a low global cognitive score (odds ratio—OR: 1.23, 95% CI: 1.01–1.50; OR: 1.47, 95% CI: 1.17–1.79, respectively). Both short sleepers and long sleepers had an increased risk of self-reported poor memory (OR: 1.63, 95% CI: 1.39–1.91; OR: 1.48, 95% CI: 1.25–1.74, respectively). No differences in the above associations were found for income, education, and urbanity. In conclusion, both the short and long sleep duration were associated with declined cognition and memory. Maintaining a normal sleep duration may aid in the prevention of cognitive function decline in older adults.