von Willebrand Factor as Marker of Vascular Function in South African Women: The POWIRS Study

Background The increasing prevalence of hypertension and vascular-related morbidity and mortality among Africans emphasizes the need to identify markers for the early detection of vascular disease. Caucasian-based studies demonstrate that the von Willebrand factor (vWf) is a useful marker of vascular dysfunction. We investigated whether associations between this marker and markers of cardiovascular function in Caucasian women are comparable with African women. Methods The study consisted of apparently healthy African (n = 99) and Caucasian (n = 114) women (mean age, 31.0 years), individually matched for age and body mass index. We measured blood pressure and arterial compliance noninvasively, and vWf in serum. We assessed univariate and multivariate-adjusted associations of blood pressure and arterial compliance with vWf. Results Although no ethnic difference existed for mean vWf levels, Caucasian and African women showed opposite associations of blood pressure and arterial compliance with vWf after single, partial, and multiple regression analyses. In Caucasians, after full adjustment, systolic (β = +0.179; P < 0.05) and diastolic (β = +0.190; P < 0.05) blood pressure correlated positively and arterial compliance negatively (β = −0.197; P < 0.01) with vWf. Conversely, in Africans, systolic blood pressure correlated weakly, but negatively (β = −0.168; P = 0.059) with vWf. However, this opposite tendency seemed due to the confounding influence of the depot medroxyprogesterone acetate (DMPA) contraceptive injection and, although >99% power existed, significance disappeared after excluding these subjects (β = −0.071; P = 0.46). Conclusions Associations of vWf with blood pressure and arterial compliance were not comparable between Caucasian and African women, suggesting that the vWf may not be a useful marker of vascular alterations in African women.