Public Health.

Background: A growing body of literature suggests that poor sleep has a negative effect on cognition. However, most prior research has predominantly used subjective sleep data and focused on non-Hispanic White (NHW) populations. Our goal was to explore the associations between objective sleep characteristics and cognition in a racially/ethnically diverse cohort.

Method: We studied 855 participants from the Health and Aging Brain Study-Health Disparities (HABS-HD)-Dormir study. Objective sleep characteristics, including nighttime sleep duration, wake after sleep onset (WASO), sleep efficiency, and sleep fragmentation index, were assessed by 7-day wrist actigraphy. Using a battery of cognitive tests, we created four cognitive composite z-scores for executive function, attention, language, and memory. We used multivariable linear regressions to examine the associations between sleep characteristics and cognitive function, adjusting for age, race/ethnicity, sex, education, marital and cognitive status. Stratified analyses based on race/ethnicity were performed in the presence of interaction.

Result: We studied 370 (43.3%) NHW, 292 (34.2%) Mexican American (MA), and 193 (22.6%) Black participants, with an average age of 66.7 (±8.4) years, and 65.1% female. Compared to NHW participants, both MA and Black participants had shorter sleep duration (7.5, 7.2, and 7.1 hours, respectively, p<0.0001), higher WASO (44.5, 57.0, 61.0 min, p<0.0001), lower sleep efficiency (91.0, 88.0, and 87.0%, p<0.0001), and higher sleep fragmentation index (24.0, 27.2, and 31.9, p<0.0001). Across the sample, longer sleep duration (per 1 hour; β = -0.048; p = 0.01) and higher WASO (per 30 min; β = -0.041; p = 0.06) were associated with worse executive function. Better sleep efficiency (per 5%; β = 0.080; p = 0.02) was associated with better executive function whereas higher sleep fragmentation index (per 10%; β = -0.074; p = 0.06) was associated with worse executive function in Black participants (p interaction = 0.07 and 0.008, respectively). Moreover, higher WASO (per 30 min; β = 0.075; p = 0.04) and higher sleep fragmentation index (per 10%; β = 0.072; p = 0.05) were associated with better attention function in Black participants (p interaction = 0.07 and 0.06, respectively).

Conclusion: These findings indicate associations between poor sleep and both executive function and attention; and highlight evidence for racial/ethnic disparities across these relationships.