Sleep quality and cognitive impairment in older Chinese: Guangzhou Biobank Cohort Study

Background evidence concerning the relationship between sleep quality and cognitive impairment is limited and inconsistent. Objective to examine the association of sleep quality with memory impairment and poor cognitive function in a large sample of older Chinese. Methods 15,246 participants aged 50+ years of the Guangzhou Biobank Cohort Study who attended the second physical examination from 2008 to 2012 were included. Sleep quality was assessed using Pittsburgh Sleep Quality Index (PSQI), and cognitive performance was assessed using both Delayed Word Recall Test (DWRT) and Mini-Mental State Examination (MMSE). Memory impairment was defined by DWRT score < 4 and poor cognitive function by MMSE score < 25. Results after adjusting for potential confounders, lower habitual sleep efficiency was associated with a higher risk of memory impairment and poor cognitive function with a dose-response pattern (both P for trend <0.001). The adjusted odds ratio (OR, 95% confidence interval (CI)) for poor cognitive function in those with the sleep efficiency of 75–85%, 65–75% and <65%, versus ≥85%, was 1.31 (1.12–1.53), 1.41 (1.16–1.73) and 1.33 (1.09–1.63), respectively. No association of the global PSQI score with memory impairment or poor cognitive function was found. Conclusions in older Chinese people, lower habitual sleep efficiency was associated with a higher risk of memory impairment and poorer cognitive function.