The effect of internal migration on blood pressure among a cohort of young adults in South Africa.

Given global concern over rising hypertension prevalence, especially in low-and-middle- income countries, we investigate whether migration and urban exposure is associated with higher blood pressure (BP). We use data collected over four waves between 2018 and 2022 from the Migrant Health Follow-Up Study, a longitudinal cohort study of young adults aged 18-40 at baseline who were members of households within the Agincourt Health and socio-Demographic Surveillance System located in rural northeast South Africa. Our analytic sample consists of the 1037 women and 994 men for whom we have BP measurements at both Waves 1 and 4, and who have complete socio-economic, demographic, and migration information collected in Waves 2 and 3, which we use to predict Wave 4 BP. Descriptively, our analysis shows that migration is still more common among men in contemporary South Africa compared with women, as it has been historically. However, a significant share of young adult women increasingly migrate away from their rural homes. We find evidence that migration is associated with higher longitudinal BP, net of various health and health behavior measures. This finding is especially robust for women. Further, residence in the highly urbanized Gauteng province is associated with increased BP for both men and women, but these negative effects are buffered by higher levels of education for women, and by employment for men. Our findings suggest that migration processes and urban exposure may result in experiences that result in increases in BP over 3-4 years, especially among women.