Young, non-Hispanic Black men and women exhibit divergent peripheral and cerebral vascular reactivity

Abstract

New findings: What is the central question of the study? Do peripheral and cerebral vascular function differ between young non-Hispanic Black men and women? What is the main finding and its importance? The non-Hispanic Black women in this study presented greater peripheral conduit artery and cerebrovascular reactivity, yet similar peripheral microvascular function relative to the non-Hispanic Black men. These preliminary findings suggest that young Black women and men possess divergent vascular function, possibly contributing to the unique non-Hispanic Black sex differences in cardiovascular and cerebrovascular diseases.

Abstract: In the USA, cardiovascular and cerebrovascular diseases remain more prominent in the non-Hispanic Black (BL) population relative to other racial/ethnic groups. Typically, sex differences emerge in the manifestation of these diseases, though these differences may not fully materialize in the BL population. While numerous mechanisms are implicated, differences in vascular function likely contribute. Research has demonstrated blunted vasodilatation in several vascular regions in BL versus non-Hispanic White individuals, though much of this work did not assess sex differences. Therefore, this study aimed to ascertain if indices of vascular function are different between young BL women (BW) and men (BM). Eleven BW and 15 BM (22 (4) vs. 23 (3) years) participated in this study. Each participant underwent testing for brachial artery flow-mediated dilatation (FMD), post-occlusive reactive hyperaemia and cerebral vasomotor reactivity during rebreathing-induced hypercapnia. BW exhibited greater adjusted FMD than BM (P < 0.05 for all), but similar or lower reactive hyperaemia when assessed as blood velocity (P > 0.39 for all) or blood flow reactivity (P < 0.05 for all), respectively. Across a range of hypercapnia, BW had greater middle cerebral artery blood velocity and cerebrovascular conductance index than BM (P < 0.001 for both). These preliminary data suggest that young BW have greater vascular function relative to young BM, though this was inconsistent across different indices. These findings provide insight into the divergent epidemiological findings between BM and BW. Further research is needed to elucidate possible mechanisms and relate these physiological responses to epidemiological observations.

Keywords: cardiovascular disease; cerebrovascular disease; non-Hispanic Black; vascular function.

Figure 1:

Allometrically scaled brachial artery flow-mediated dilation (FMD; A), shear area-under-the-curve (AUC; B), incremental flow AUC (C), and total flow AUC (D) responses to a brief period of forearm ischemia. Shear AUC and flow AUC are summed from end-occlusion to peak brachial artery dilation. Data are from 11 BW and 15 BM. Panel A was analyzed using an analysis of covariance, while Panels B-D were analyzed using two-tailed, unpaired, Welch’s t-tests. (*): P < 0.05

Figure 2:

Absolute cerebral vascular conductance index (CVCi; A) and the slope of the partial end-tidal CO₂ tension (P_ETCO₂) and CVCi relation (i.e., cerebrovascular reactivity; CVR; B) at baseline and during rebreathing-induced hypercapnia. BW are represented by squares and BM are represented by circles. Data are from 11 BW and 15 BM, except for a P_ETCO₂ of Δ12 mmHg, whereby only 8 BW reached this stage of hypercapnia. CVR is measured as the change in blood velocity per unit change in blood pressure, per unit change in P_ETCO₂. Data were analyzed using a mixed-effects model (panel A) and a two-tailed, unpaired, Welch’s t-test (panel B). (*): P < 0.05 between BW and BM at each P_ETCO₂ stage for panel A and between the slopes in panel B.

Figure 3:

Relative cerebral vascular conductance index (ΔCVCi; A) and the slope of the partial end-tidal CO₂ tension (P_ETCO₂) and ΔCVCi relation (i.e., cerebrovascular reactivity; CVR; B) at baseline and during rebreathing-induced hypercapnia. BW are represented by squares and BM are represented by circles. Data are from 11 BW and 15 BM, except for a P_ETCO₂ of Δ12 mmHg, whereby only 8 BW reached this stage of hypercapnia. Data were analyzed using a mixed-effects model (panel A) and a two-tailed, unpaired, Welch’s t-test (panel B). (*): P < 0.05 between BW and BM at each P_ETCO₂ stage for panel A and between the slopes in panel B.