Background: Short and long sleep duration are associated with increased mortality and worse global cognitive function, but is unclear if these relations persist after accounting for the risk of sleep disordered breathing (SDB). The aim of our study is determine the association between short and long sleep duration with worse global cognitive function in a racially/ethnically diverse elderly cohort.
Methods: We examined sleep hours and global cognitive function cross-sectionally within the population-based Northern Manhattan Study cohort. We conducted nonparametric and logistic regression to examine associations between continuous, short (< 6 h) and long (≥ 9 h) sleep hours with performance on the Mini Mental State Examination (MMSE).
Results: There were 927 stroke-free participants with data on self-reported sleep hours and MMSE scores (mean age 75 ± 9 years, 61% women, 68% Hispanics). The median (interquartile range) MMSE was 28 (10-30). Sleep hours (centered at 7 h) was associated with worse MMSE (β = -0.01; SE [0.004], p = 0.0113) adjusting for demographics, vascular risk factors, medications, and risk for SDB. Reporting long sleep (≥ 9 h) compared to 6 to 8 h of sleep (reference) was significantly and inversely associated with MMSE (adjusted β = -0.06; SE [0.03], p = 0.012), while reporting short sleep was not significantly associated with MMSE performance. Long sleep duration was also associated with low MMSE score when dichotomized (adjusted OR: 2.4, 95% CI: 1.1-5.0).
Conclusion: In this cross-sectional analysis among an elderly community cohort, long sleep duration was associated with worse MMSE performance.
Keywords: Sleep duration; cognition; cognitive impairment; long sleep; mini mental score; short sleep.