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

Abstract

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.

Keywords: African American; delayed sleep phase; depression; health disparities.

Figure 1. Weekday bedtime.

Percentage of individuals who report a weekday bedtime later than a given hour between 9:00 PM and 4:00 AM. African Americans (blue) were more likely to report a later bedtime at all time points after 10:00 PM (P < .01 for all) compared to non-Hispanic whites (red). No individuals reported a bedtime later than 4:00 AM.

Figure 2. Delayed sleep onset.

Proportion of individuals with delayed sleep time (sleep time after midnight) are shown for African Americans (red) and non-Hispanic whites (green) in the left panel. In the right panel, the adjusted odds ratio for delayed sleep time in African Americans is shown in comparison to non-Hispanic whites. Note the greater prevalence of delayed sleep time in African Americans.

Figure 3. Relationship between delayed sleep time and depression.

Odds ratios (unadjusted and adjusted) for the relationship between delayed sleep time (sleep time after midnight) and depression are shown for all participants combined (African Americans and non-Hispanic whites; left panel) and after excluding individuals receiving antidepressants (right panel). Individuals without delayed sleep time served as the reference population (dashed horizontal line). Note that the finding of association between delayed sleep time and depression remained after such sensitivity analysis.

Figure 4. Delayed sleep time by age.

Percentage of individuals with delayed sleep time (sleep time after midnight) are shown for African Americans (blue) and non-Hispanic whites (red) by age. Note that while the likelihood of delayed sleep is time is relative stability over age in African Americans, there is an age-associated increased likelihood of delayed sleep time in whites. Data are presented for mean age and one standard deviation above and below the mean.