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-Ostberg 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.