Investigating the impact of early-life, life-course and genetic factors on blood pressure among young Africans

Background: The relationship between blood pressure (BP) and early-life factors such as birth weight, life-course factors such as obesity, and genetic variants among Africans are unknown. This PhD aimed to systematically review literature on the relationship between birth weight and BP among young Africans and to use data from the Entebbe Mother and Baby Study (EMaBS), a Ugandan birth cohort, to investigate the impact of early-life, life-course and genetic factors on adolescents’ BP. Methods: Four databases were systematically searched for relevant publications. In the EMaBS, data were collected prenatally from pregnant women and prospectively from the resulting offspring, with BP measured in adolescence. Linear regression was used to relate birth weight, early-growth and other characteristics to BP. Genetic analyses were conducted to investigate genetic variants associated with adolescents’ BP. Results: The systematic review showed that among the few published studies from Africa, the relationship between birth weight and BP varied by participants’ age. Findings from the EMaBS indicated strong evidence of association between postnatal weight gain and later BP, with fast-growing low birth weight individuals particularly affected. Maternal factors positively associated with higher adolescent BP were gestational body mass index (BMI) and higher education status. Adolescent factors positively associated with higher BP were age, waist circumference, BMI, family history of hypertension and current Trichuris infection. Previous malaria infection in childhood and higher vegetable or fruit consumption were associated with lower BP in adolescence. No genetic variant reached genome-wide significance for association with BP. Thirty-three of 330 variants previously identified as associated with BP were replicated in this study, but none were significant after accounting for multiple testing. Conclusions: Postnatal weight gain rather than birth weight is associated with later BP, with fast-growing low birth weight individuals at particular risk. Larger studies are required to characterise BP genetics in African adolescents.