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.