UC Irvine

Background: Cardiovascular health disparities between African Americans (AA) and European Americans (EA) persist despite established evidence that AA populations exhibit higher heart rate variability (HRV), a cardioprotective marker of parasympathetic function. Previous research has demonstrated that higher HRV predicts lower blood pressure in EA but not AA individuals, and these relationships may be further modulated by sex differences. However, the intersectional effects of race and sex on HRV's relationship with cardiovascular measures remain incompletely understood.

Methods: Secondary analyses were conducted using data from the Augusta Heart Study cohort (N=385; 207 AA, 178 EA; 54% female). Participants underwent baseline cardiovascular assessment and 6-year follow-up (mean interval = 6.32 years). High-frequency HRV and comprehensive cardiovascular measures were collected at baseline (T1). Blood pressure (BP), total peripheral resistance (TPR), cardiac output, and related hemodynamic indices were measured at both time points. Hierarchical regression and moderation analyses examined relationships between T1 HRV and follow-up (T2) cardiovascular measures.

Results: AA participants showed significantly higher BP, TPR, and mean arterial pressure than EA at both time points (all p < .001). Higher T1 HRV predicted lower T2 BP measures in EA men (β = -2.498, p = .014) but not in AA participants. Among AA participants, women exhibited higher baseline BMI, systolic BP, diastolic BP, and TPR (all p < .05), while men showed higher BP at follow-up (p < .001). Three-way interactions between race, sex, and HRV were non-significant, though conditional effects indicated race and sex moderated the HRV-TPR index association specifically in AA men.

Conclusions: These findings demonstrate distinct patterns of cardiovascular regulation between AA and EA populations and reveal important sex differences within racial groups. Results suggest the relationship between autonomic regulation and cardiovascular function varies by both race and sex, potentially reflecting biological factors and psychosocial influences. Future research should employ experimental designs with larger, balanced samples to further elucidate these relationships.