Habitual Sleep Duration and Sleep Effciency Do Not Mediate the Relationship Between Race and Nocturnal Blood Pressure Dipping in Young Black and White Women

Abstract

Blunted nocturnal blood pressure (BP) dipping, defined as less than 10% reduction in BP during sleep as compared to wake, independently predicts cardiovascular disease. Short and disturbed sleep associate with less nocturnal BP dipping in young adults, and Black women (BLW) demonstrate less nocturnal BP dipping and poorer sleep health compared to White women (WHW) as early as young adulthood. However, not known is if habitual, objectively estimated sleep metrics mediate the relationship between race and BP dipping in young women. Thus, this study sought to evaluate the mediating effect of objectively estimated habitual sleep duration and sleep effciency on the relationship between race and nocturnal BP dipping in apparently healthy, young BLW and WHW. We hypothesized that BLW would have lower nocturnal systolic and diastolic BP dipping than WHW, but that the relationship between race and nocturnal BP dipping would be at least partly mediated by sleep duration and sleep effciency. Participants were 18-29 years, female, normotensive, nonobese, without evidence of clinical sleep disorders, and self-identified their race as Black or White. Systolic and diastolic BP dipping were each derived from 24-hour ambulatory BP monitoring by subtracting mean asleep BP from mean awake BP, divided by mean awake BP, *100. Sleep duration (total sleep time between sleep onset and offset) and sleep effciency (total sleep time divided by total time in bed dedicated to sleep, *100) were measured via wrist actigraphy for 14 consecutive nights, and means were generated. Race differences in BP dipping and habitual sleep metrics were assessed via independent-samples t-tests. The standard mediation model as proposed by Baron and Kenney (1986) was used to assess the mediating effect of habitual sleep duration and sleep effciency on the relationship between race and systolic and diastolic BP dipping. Participants included 20 BLW (22±3 years) and 17 WHW (25±3 years). Systolic BP dipping (BLW: 9.5±5.9%, WHW: 13.9±5.1%, p=0.02) and diastolic BP dipping (BLW: 16.3±7.3%, WHW: 21.9±5.5%, p=0.01) were lower among BLW. Sleep duration was not different between races (BLW: 6.7±0.5 hrs, WHW: 7.0±0.7 hrs, p=0.14), though sleep effciency was lower among BLW (BLW: 81.6±4.4%, WHW: 86.0±3.1%, p<0.01). In contrast to our hypothesis, neither habitual sleep duration nor sleep effciency significantly mediated the relationship between race and BP dipping (all indirect effects p>0.38). Habitual sleep metrics did not explain race differences in nocturnal BP dipping between young BLW and WHW; thus, future work should consider other physiological, social, or environmental determinants of BP dipping in young BLW. University of Delaware Research Foundation — Strategic Initiative Grant (MAW/FP) and AHA Award #831488 (EH). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.