Quantifying the temporal changes in geographical-level contributions of risk factors to hypertension (2008-2017): Results from national surveys.

South Africa has one of the world's highest proportions of hypertensive individuals, which has become a major public health problem. Understanding the temporal and spatial patterns in hypertension rates is crucial for evaluating the existing prevention and care models, which have not been fully understood in South Africa. The geoadditive models were used to quantify the geographical clustering of hypertension in the Black South African population enrolled in the most recent cross-sectional national surveys (2008-2017). Population-attributable risks were calculated for modifiable risk factors. 80,270 men (41%) and women (59%) aged 15+ were included. Using the 2017 guidelines, 52% of the men and 51% of the women were classified as hypertensive. As expected, these proportions were slightly lower when we used the previous guidelines (48% and 47% for men and women, respectively). There was significant geospatial heterogeneity in hypertension prevalence with substantial province-specific disparities. Western, Northern, and Eastern Capes were the most significant provinces, with >50% of the hypertensive men and women. The population-level impact of obesity remained high in all provinces, where 33%-to-57% and 47%-to-65% of hypertensives were exclusively associated with obese/overweight men and women respectively. Despite some improvements in certain areas, most of the country is behind the targeted levels set in 2011/2013. Identifying the most relevant risk factors and their sub-geographical-level contributions to hypertension may have significant public health implications for developing and implementing cost-effective prevention programs to raise awareness of healthy diet and lifestyle behaviours.