Are behavioural risk factors to be blamed for the conversion from optimal blood pressure to hypertensive status in black South Africans? A 5-year prospective study

Abstract

Background Longitudinal cohort studies in sub-Saharan Africa are urgently needed to understand cardiovascular disease development. We, therefore, explored health behaviours and conventional risk factors of African individuals with optimal blood pressure (BP) (4120/80mm Hg), and their 5-year prediction for the development of hypertension. Methods The Prospective Urban Rural Epidemiology study in the North West Province, South Africa, started in 2005 and included African volunteers (n¼1994; aged430 years) from a sample of 6000 randomly selected households in rural and urban areas. Results At baseline, 48% of the participants were hypertensive (5140/ 90 mmHg). Those with optimal BP (n¼478) were followed at a success rate of 70% for 5 years (213 normotensive, 68 hypertensive, 57 deceased). Africans that became hypertensive smoked more than the normotensive individuals (68.2% vs 49.8%), and they also had a greater waist circumference [ratio of geometric means of 0.94cm (95% CI: 0.86–0.99)] and greater amount of g-glutamyltransferase [0.74 U/l (95% CI: 0.62–0.88)] at baseline. The 5-year change in BP was independently explained by baseline g-glutamyltransferase [R2¼0.23, b¼0.13 U/l (95% CI: 0.01–0.19)]. Alcohol intake also predicted central systolic BP and carotid cross-sectional wall area (CSWA) at follow-up. Waist circumference was another predictor of BP changes [b¼0.18 cm (95% CI: 0.05–0.24)] and CSWA. HIV infection was inversely associated with increased BP. Conclusions During the 5 years, 24% of Africans with optimal BP developed hypertension. The surge in hypertension in Africa is largely explained by modifiable risk factors. Public health strategies should focus aggressively on lifestyle to prevent a catastrophic burden on the national health system.