African Genetic Ancestry is Associated with Sleep Depth in Older African Americans

Abstract

Study objectives: The mechanisms that underlie differences in sleep characteristics between European Americans (EA) and African Americans (AA) are not fully known. Although social and psychological processes that differ by race are possible mediators, the substantial heritability of sleep characteristics also suggests genetic underpinnings of race differences. We hypothesized that racial differences in sleep phenotypes would show an association with objectively measured individual genetic ancestry in AAs.

Design: Cross sectional.

Setting: Community-based study.

Participants: Seventy AA adults (mean age 59.5 ± 6.7 y; 62% female) and 101 EAs (mean age 60.5 ± 7 y, 39% female).

Measurements and results: Multivariate tests were used to compare the Pittsburgh Sleep Quality Index (PSQI) and in-home polysomnographic measures of sleep duration, sleep efficiency, apnea-hypopnea index (AHI), and indices of sleep depth including percent visually scored slow wave sleep (SWS) and delta EEG power of EAs and AAs. Sleep duration, efficiency, and sleep depth differed significantly by race. Individual % African ancestry (%AF) was measured in AA subjects using a panel of 1698 ancestry informative genetic markers and ranged from 10% to 88% (mean 67%). Hierarchical linear regression showed that higher %AF was associated with lower percent SWS in AAs (β (standard error) = -4.6 (1.5); P = 0.002), and explained 11% of the variation in SWS after covariate adjustment. A similar association was observed for delta power. No association was observed for sleep duration and efficiency.

Conclusion: African genetic ancestry is associated with indices of sleep depth in African Americans. Such an association suggests that part of the racial differences in slow-wave sleep may have genetic underpinnings.

Keywords: African Americans; genetic admixture; race; slow wave sleep.

Figure 1

Distribution of individual African ancestry (%AF) within self-identified African Americans in SleepSCORE. %AF distribution in African Americans ranged between 10% and 88% with a mean of 67% (standard deviation 16%).

Figure 2

In African Americans, visually scored percent slow wave sleep (SWS) varies inversely with individual African ancestry. The Y axis shows percent SWS values adjusted for covariates and the X axis shows % African ancestry. (A) Percent SWS values were adjusted for age, sex, and body mass index (BMI) excluding individuals with %AF < 0.33 (outliers removed; n = 66). (B) Percent SWS values were adjusted for age, sex, BMI, AHI, sleep medication use, antidepressant use, and socioeconomic status (n = 63; three individuals with missing SES data not included in analyses).

Figure 3

In African Americans, nonrapid eye movement electroencephalography (NREM EEG) delta power (QEEG-δ) varies inversely with individual African ancestry. The Y axis shows QEEG-δ values adjusted for covariates and the X axis shows % African ancestry. (A) QEEG-δ adjusted for age, sex, and BMI in individuals with %AF > 33% (outliers removed; n = 66). (B) QEEG-δ adjusted for age, sex, BMI, AHI, sleep medication use, antidepressant use, and socioeconomic status (n = 63 excluding three individuals with missing SES data).