Contribution of systemic blood flow to hypertension in Africa

Of all deaths caused by cardiovascular disease, 80% occur in low-to-middle income countries.In Africa, the dominant risk factor is unquestionably, hypertension.Hypertension is more prevalent and often associated with worse target organ damage in groups of African descent.Hypertension in those of African ancestry is frequently a low-renin form, possibly mediated by a genetic predisposition to salt sensitivity.This genetic predisposition is thought to reflect a greater ability of ancestors of those of African descent, to survive the harsh conditions of slave ships, or an evolutionary change which enabled survival in hot, arid, equatorial environments.Although salt-sensitivity has previously been attributed to renal mechanisms, contemporary thought has challenged this notion.Alternative hypotheses include abnormalities in the handling of salt in subcutaneous tissue.These arguments originated from the evidence that salt-sensitivity is a vascular response to salt loading, with little evidence for even a modest increase in systemic flow.Some evidence for increases in systemic flow would support a vascular autoregulatory response to renal-related increases in systemic flow.However, our group have now provided the evidence that a persistent increase in systemic flow does occur in Africa and that this is a fundamental determinant of hypertension across the adult age.