Sleep, inflammation and cognitive function in middle-aged and older adults: A population-based study

Background: Sleep plays a key role in preserving cognitive function. However, the optimal strategies of sleep for cognition and the underlying mechanism are not well-established. Methods: A cross-sectional study was performed using the China Health and Retirement Longitudinal Study (CHARLS), 2011-2012 survey. Self-reported nighttime sleep and afternoon napping data were collected. Fasting blood collected was analyzed for the high-sensitivity C-reactive protein (CRP) and white blood cell. Results: Both nighttime sleep and afternoon napping were significantly associated with cognition after adjusting for confounders (p < 0.05). Precisely, participants with nighttime sleep of 6.1-7h had the highest cognition scores (p < 0.05). Participants with less than 30 min afternoon napping had the highest cognition scores (p < 0.05). The synergistic effect of nighttime sleep and afternoon napping was not significant (p > 0.05). Nighttime sleep and afternoon napping were significantly related to the white blood cell, but not the high-sensitivity CRP. The white blood cell mediated the association between sleep and cognition (p < 0.05). Conclusion: Nighttime sleep of six to seven hours and afternoon napping of less than 30 minutes are associated with optimal cognitive function in middle-aged and older people, respectively. Sleep influences cognition partly via the inflammatory profile.