Habitual Sleep Duration and Efficiency Do Not Explain Race Differences in Blood Pressure Dipping Between Young Black and White Women

Department of Kinesiology and Applied Physiology

University of Delaware

Impaired nocturnal blood pressure (BP) dipping is an independent predictor of cardiovascular disease. Habitually short and disturbed sleep are linked to less BP dipping in young adults. Black women (BLW) demonstrate less BP dipping and worse sleep compared to White women (WHW) as early as young adulthood. However, previous studies have failed to consider the impact of habitual, objectively estimated sleep on race differences in BP dipping. Thus, this study sought to evaluate the influence of objectively estimated habitual sleep duration and sleep efficiency on race differences in BP dipping between apparently healthy, young adult BLW and WHW. We hypothesized that Black race would significantly predict less BP dipping, but the association would be weakened after adjusting for habitual sleep duration and sleep efficiency. Participants were normotensive, nonobese, free of sleep disorders, and self-identified their race as Black or White. Sleep duration and sleep efficiency were objectively estimated via wrist actigraphy for 14 consecutive nights, and mean values were generated. Systolic and diastolic BP dipping were derived from 24-hour ambulatory BP monitoring as the difference between their respective awake and asleep BP, divided by awake BP, *100. Associations between race and BP dipping were evaluated using linear regression models of BP dipping. Models were also adjusted for habitual sleep duration and sleep efficiency. Participants included 17 BLW (22±3 yrs) and 17 WHW (25±3 yrs). Black race significantly predicted less systolic (β=-4.85, SE=1.96, p=0.02) and diastolic BP dipping (β=-5.66, SE=2.29, p=0.02). Adjustment for habitual sleep metrics attenuated the association between race and systolic BP dipping (β=-4.37, SE=2.29, p=0.06), but race remained a significant predictor of diastolic BP dipping (β=-6.30, SE=2.66, p=0.03). Habitual sleep does not explain the observed race differences in BP dipping in our sample of young BLW and WHW, thus other social or environmental factors should be considered.