Hypertension prevalence and risk factors in a retained high-risk cohort of rural Black adults: a five-year follow-up study in Limpopo Province, South Africa

Hypertension remains a significant public health concern in South Africa, particularly in rural areas where healthcare access is limited. This study aimed to longitudinally assess hypertension prevalence and associated risk factors among a retained cohort of rural Black adults in Limpopo Province. Prospective longitudinal cohort study of 518 participants followed from baseline (2014–2016) to follow-up (2019–2022). Data were analyzed using SPSS version 27.0, with binary logistic regression to determine factors associated with hypertension. Among the retained cohort ( n = 518), baseline hypertension prevalence was 43.8%, increasing to 46.9% at follow-up. Hypertensive participants were significantly older and more likely to be female. Adjusted analyses showed age ≥ 64 years (baseline aOR = 3.05; 95% CI:1.23–7.56; follow-up aOR = 2.72; 95% CI:1.43–5.18), central obesity (baseline aOR = 2.92; 95% CI:1.72–4.96; follow-up aOR = 2.60; 95% CI:1.69–3.99), and diabetes (baseline aOR = 2.92; 95% CI:1.38–6.17; follow-up aOR = 2.75; 95% CI:1.70–4.44) were consistently associated with hypertension. Notably, significant attrition bias was observed: baseline hypertension prevalence among retained participants was more than double that of those lost to follow-up (43.8% vs. 19.7%; p < 0.001), and retained participants had higher rates of obesity and diabetes but lower rates of kidney disease. In this selectively retained high-risk cohort, hypertension prevalence increased over five years, with age, central obesity, and diabetes as consistent risk factors. Due to substantial attrition bias, these findings should be interpreted as reflecting trends within a high-risk survivor sub-cohort rather than population-level prevalence estimates. The strong associations observed support targeted screening and intervention strategies for older adults, women, and individuals with obesity or diabetes in rural South African communities.