Differences in sleep timing and related effects between African Americans and non-Hispanic Whites.

STUDY OBJECTIVES: Prior studies have shown a morning chronotype for African Americans compared with non-Hispanic Whites, yet self-reported sleep timing is delayed in African Americans compared with Whites. METHODS: We analyzed data from the Multi-Ethnicity Study of Atherosclerosis, a multisite community-based cohort. Self-reported and actigraphic sleep timing, chronotype measured by the modified Horne-Östberg Morningness-Eveningness Questionnaire, and risk of depression measured by the Center for Epidemiologic Studies Depression scale were examined using nonparametric approaches and linear or logistic regression while comparing between African Americans and Whites and evaluating the effects of delayed sleep phase. RESULTS: In 1,401 participants, there was no difference in chronotype between African Americans and Whites. African Americans were 80% more likely to report a delayed sleep phase (defined as bedtime after midnight) on weekdays and 50% more likely on weekends than were Whites. Actigraphic data showed similar results. Actigraphic midsleep time was delayed 38 minutes on weekdays and 24 minutes on weekends in African Americans compared with Whites. Stratified analysis by chronotype showed that African Americans with a morning or intermediate chronotype had a significantly delayed sleep phase compared with Whites, but there was no difference between African Americans and Whites with an evening chronotype. Delayed sleep phase was associated with depression, but this relationship was only significant in White participants. CONCLUSIONS: African Americans had a delayed sleep phase compared with Whites that was more pronounced in individuals with a morning or intermediate chronotype. Consequences of delayed sleep phase may vary by race and ethnicity.

Delayed Sleep Time in African Americans and Depression in a Community-Based Population.

STUDY OBJECTIVES: Studies have shown racial differences in circadian rhythm in African Americans when compared to non-Hispanic whites, and an association between circadian dyssynchrony and depression. We hypothesized that the prevalence of delayed sleep time is greater in African Americans when compared to whites and that delayed sleep time is associated with depression. METHODS: We analyzed data from the Sleep Heart Health Study (SHHS), a large community-based sample. Delayed sleep time was defined as self-reported weeknight bedtime after midnight. Depression was defined based on participant's response to the question, "In the past 4 weeks have you felt downhearted and blue?" or reported antidepressant use. We performed multivariate linear and logistic regression, adjusting for age, sex, race, body mass index, smoking, apnea-hypopnea index, alcohol use, and caffeine consumption. RESULTS: Adjusted weekday bedtime was 15 ± 7 minutes later in African Americans compared to whites (P < .001). Similarly, weekend bedtime was 18 ± 7 minutes later in African Americans compared to whites (P = .025). The prevalence of delayed sleep time was greater in African Americans (33.3%) compared to whites (18.7%; P < .001). After adjusting for confounders, when compared to whites, a greater proportion of African Americans had delayed sleep time (adjusted odds ratio [aOR] 2.03; 95% confidence interval [95% CI] 1.5, 2.4; P < .0001). Depression was independently associated with delayed sleep time after adjustment (aOR 1.4; 95% CI 1.1, 1.7; P = .007). CONCLUSIONS: African Americans are more likely to have a delayed sleep time compared to whites, and delayed sleep time was independently associated with depression.