Impaired peripheral and cerebral microvascular function / reactivity in healthy young African Americans

African Americans (AA) are at an increased risk for cardio and cerebral vascular disease relative to Caucasians (CA) and the underlying impairments manifest as early as the second generation prior to overt signs of risk. The mechanisms of this increased risk are multifactorial; however, evidence suggests that microvascular dysfunction is a primary contributor. This study tested the hypothesis that microvascular function, indexed by the skin vascular conductance (SkVC) response to local heating, is impaired in young otherwise healthy AAs. Furthermore, we hypothesized that AAs have an attenuated cerebral vasodilator response to hypercapnia. Nineteen healthy young individuals were participated in this study (9 AAs, 10 CAs). SkVC was assessed while the skin was clamped at 34 °C and 40 °C and values were normalized to a maximal value obtained during heating at 43 °C for 30 min. Cerebral vasomotor reactivity (CVMR) was assessed by increases in cerebral vascular conductance (CVC) during a rebreathing protocol. SkVC was lower in the AA group at 34 °C (AA: 10±3 % max vs. CA: 16±7 % max; P < 0.01) In addition, SkVC was reduced in AAs at 40 °C (AA: 56±15 % max vs. CA: 68±12 % max; P=0.03). CVMR was significantly attenuated during hypercapnic rebreathing in AAs relative to CAs (AA: 2.8 ± 1.2 %CVC/Torr vs. CA: 5.7 ±0.9 %CVC/Torr; P < 0.001). Our findings suggest that microvascular function is impaired in young otherwise healthy AAs.