Spontaneous Cardiac Baroreflex Sensitivity in Young, Healthy Black and White Adults: Influence of Race and Sex

Abstract

Background: Black (BL) individuals living in the United States are more likely to develop hypertension and cardiovascular disease compared to their White (WH) counterparts. However, studies investigating racial differences in blood pressure regulation and baroreflex sensitivity (BRS) are limited and have reported equivocal results. Furthermore, despite BL females also having a high prevalence of hypertension and cardiovascular disease, sex differences are often not considered. Additionally, baroreflex effectiveness index (BEI) is a newer measure used to estimate baroreflex function, yet studies have not examined the influence of sex or race on BEI. Therefore, the purpose of this project was to investigate the effects of both race and sex on cardiac BRS and BEI. We hypothesized that BL individuals would have lower cardiac BRS and BEI than WH individuals. Methods: We studied 88 young healthy adults, 28 BL males (21 ± 3 years; mean ± SD), 17 WH males (24 ± 4 years), 15 BL females (21 ± 3 years), and 28 WH females (23 ± 4 years). Heart rate (ECG) and beat-to-beat arterial blood pressure (finger photoplethysmography) were continuously recorded during a five-minute resting baseline. Cardiac BRS was measured using the Sequence Method, by identifying the gain of the relationship between systolic blood pressure and RRI from sequence(s) of three or more consecutive heartbeats in which systolic blood pressure and RRI change in the same direction. BEI was quantified by baroreflex-driven ramps relative to all systolic blood pressure ramps. Results: Cardiac BRS was significantly higher in BL individuals (31 ± 15 ms/mmHg) compared to WH individuals (25 ± 11 ms/mmHg; main effect of race, p = 0.02). Interestingly, post hoc comparisons revealed that this was only true within the males (p = 0.03), but not females (p = 0.63). However, there was no difference in cardiac BRS between males and females (main effect of sex, p = 0.35) and no interaction between sex and race (p = 0.27). There were also no effects of race (p = 0.65) or sex (p = 0.15) on BEI. Conclusion: These preliminary data suggest that, in contrast to our hypothesis, young BL individuals have higher cardiac BRS compared to WH individuals; an effect that is only present in males. In contrast, BEI was not influenced by race or sex. Collectively, our findings do not suggest that lower cardiac BRS plays a major role in the higher prevalence of cardiovascular disease in BL individuals. This is the full abstract presented at the American Physiology Summit 2023 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.