STUDY OBJECTIVES: To evaluate the association between sleep duration and neurocognitive function in a representative sample of middle-aged to older Hispanic/Latino adults in the US. We tested the hypothesis that sleep duration has a nonlinear, inverted U-shaped association with neurocognitive function.
METHODS: We performed a cross-sectional analysis from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) participants ages 45-74 years (n = 8,676). HCHS/SOL is a community-based cohort from four US urban areas sampled using a probability design from 2008-2011. Self-reported sleep duration was calculated as a weighted average of the difference between habitual wake and bedtimes assessed by separate questions for weekdays and weekends. Neurocognitive function was measured with standardized scores for Word (Phonemic) Fluency (WF), Brief-Spanish English Verbal learning test (B-SEVLT), and Digit Symbol Substitution (DSS) tests.
RESULTS: The mean age was 56.5 years; 55% were women; and 40.4% had less than high school education. Average sleep duration was 7.8 ± 1.7 hours. There was an inverted U-shaped association with sleep duration and WF, B-SEVLT sum, and the DSS, with no association with B-SEVLT delayed-recall. Participants with intermediate sleep duration had the best neurocognitive function, while long sleepers had worse neurocognitive function adjusting for demographic, behavioral, and medical factors, daytime sleepiness, and use of sleep medications.
CONCLUSIONS: Sleep duration had curvilinear inverted U-shaped associations with neurocognitive function, with worse scores among participants with longer sleep duration. These findings may provide a framework to further examine sleep duration in the prevention and treatment of neurocognitive disorders.