Night Sleep Duration and Risk of Cognitive Impairment in a Chinese Population: A Cross-sectional Study.

Objective: Although sleep is one of the most important health-related behavioral factors, the association between night sleep duration and cognitive impairment has not been fully understood. A cross-sectional study was conducted with a random sample of 2,514 participants (⋝ 40 years of age; 46.6% women) in China to examine the association between night sleep duration and cognitive impairment.

Methods: Night sleep duration was categorized as ⋜ 5, 6, 7, 8, or ⋝ 9 h per night. Cognitive function was measured using the Mini-Mental State Examination. A multivariate regression analysis was used to analyze the association of night sleep duration with cognitive impairment. A total of 122 participants were diagnosed with cognitive impairment.

Results: A U-shaped association between night sleep duration and cognitive impairment was found. The odds ratios (95% confidence intervals) of cognitive impairment (with 7 h of daily sleep being considered as the reference) for individuals reporting ⋜ 5, 6, 8, and ⋝ 9 h were 2.14 (1.20-3.83), 1.13 (0.67-1.89), 1.51 (0.82-2.79), and 5.37 (1.62-17.80), respectively (P ⋜ 0.01).

Conclusion: Short or long night sleep duration was an important sleep-related factor independently associated with cognitive impairment and may be a useful marker for increased risk of cognitive impairment..