Incidence and correlates of high blood pressure from childhood to adulthood: the Birth to Twenty study

Background: There is growing evidence from high-income countries suggesting that hypertension developed in childhood and adolescence persists into adulthood. The objective of this study was to investigate the incidence and risk factors of high blood pressure (BP) in urban black children. Methods: We used data from the Birth to Twenty (BT20R) cohort in Johannesburg, South Africa constituting of children born in 1990 and who had their growth, development and blood pressure measured at six follow-up periods over the course of 13 years. High BP was classified as at least 95th percentile for age, sex and height. Incidence rate of high BP was calculated using survival analysis and risk factors were determined by use of Cox proportional hazard regression. Results: Over a follow-up period of 13 years, the overall incidence rate of high BP was 57 cases per 1000 person-years (95% CI 53.2 – 61.1). Risk for incident high BP increased with rapid relative weight gain in early childhood (hazard ratio =1.11, 95% CI 1.00 – 1.22), mid-childhood (hazard ratio = 1.13, 95% CI 1.03 – 1.24) and adolescence (hazard ratio = 1.21, 95% CI 0.99 – 1.47). Maternal parity significantly increased the risk for incident high BP (hazard ratio = 1.08, 95% CI 1.01 – 1.15). Conclusion: Maternal parity and relative weight gain were determinants for incident high blood pressure in urban black South African children and adolescents. To reduce the high incidence and the disease burden of high BP, national programs should focus on promoting healthy lifestyle in early stages of life to prevent rapid weight gain and later cardiovascular disease risk. Further research is required to investigate whether incident high BP in childhood predict clinical outcomes in adulthood.