Improvement in Sleep Duration was Associated with Higher Cognitive Function among Middle-Aged and Elderly Chinese Participants

Study objectives Rodent studies suggested that improvement in sleep duration might correlate with better cognitive function. We aimed to examine the associations between changes in sleep duration and cognitive function. Methods 10325 individuals from the China Health and Retirement Longitudinal Study (CHARLS) were included. Self-reported nocturnal sleep duration and cognitive function were assessed in CHARLS 2011, 2013 and 2015 (Wave 1, Wave 2, Wave3). Cognitive function was assessed by a global cognition score, which included three domains: episodic memory, figure drawing and Telephone Interview of Cognitive Status (TICS). Generalized additive models (GAM) and Generalized estimation equations (GEE) were used to examine the associations between baseline sleep duration and longitudinal cognitive function. We used generalized linear models (GLM) to study the associations between changes in sleep duration and cognitive function in Wave 3. Results After adjusting for potential confounders, change from short sleep duration (SSD) to moderate sleep duration (MSD) was associated with better global cognition scores (β=0.54, P <0.01). Change from SSD to long sleep duration (LSD) (β=-0.94, P <0.001) or change from LSD to SSD (β=-1.38, P <0.01) was associated with lower global cognition. For individuals with MSD, ≥2 h increase (β=-0.89, P <0.001) or decrease (β=-0.70, P <0.001) in sleep duration was associated with lower global cognition. Conclusions For short sleepers, improvement in sleep duration correlated with better cognition. For long sleepers, there was no need to reduce sleep duration. Excessive changes or deviation from the moderate duration was associated with lower cognition.