Background: Cold exposure increases arterial wave reflection to the aorta mainly through adrenergic vasoconstriction. Normotensive blacks exhibit heightened sympathetic response to cold as compared to Whites controls. We therefore decided to test the hypothesis that cold exposure would elicit a greater increase in arterial wave reflection in normotensive Africans when compared to normotensive Caucasian subjects. In addition we sought to investigate whether this would be accompanied by a higher increase in aortic pulse wave velocity (PWV) and by a more pronounced vasoconstriction of the skin microcirculation.

Methods: 17 young normotensive Africans and 17 age and weight matched Caucasians were recruited for the study. All underwent assessment of PWV and Augmentation Index corrected for heart rate (AIx) at rest, during and after hand immersion in ice water (cold pressor test, [CPT]). Concomitantly, skin microvascular blood flow response to cold was continuously monitored by laser Doppler flowmetry method.

Results: At rest, Africans exhibited higher values of PWV than Caucasians (7.3±0.3 vs 6.4±0.2 m/sec respectively, p=0.04). During CPT the magnitudes of increases in SBP and PWV were greater in Africans than Caucasians (26±3 mmHg vs 15±3 mmHg and 0.8±0.2 m/sec vs 0.4±0.2 m/sec respectively, p<0.05 for all). Additionally, CPT induced a more pronounced skin microvascular vasoconstriction in Africans as compared to Caucasians (−45±7 % vs −25±7 %, p=0.01). Finally, Africans exhibited higher AIx values during CPT (12.6±2.4 vs 5.5±2.4 %, p=0.04) when compared to Caucasian subjects.

Conclusions: Normotensive Africans exhibit intensified wave reflection to the aorta as response to CPT when compared to Caucasians. This is accompanied by a greater increase in PWV and a more pronounced vasoconstriction of the microcirculation.