Impact of early growth on blood pressure from childhood to adulthood: birth-twenty cohort
Date
2016
Authors
Kagura, Juliana
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Abstract
Background
Childhood hypertension is of great concern parallel to the obesity epidemic and early manifestation of antecedents of primary hypertension like arteriosclerosis. Patterns of early growth are associated with spiraling rates of raised blood pressure (BP) in paediatric populations. However, not much is known about early growth and its effect on BP from childhood to early adulthood. This study hypothesizes early life growth is associated with BP from childhood to adulthood.
Methods
Data for this study came from a sample of black children from the Birth to Twenty cohort study of children born in Soweto, Johannesburg in 1990. Firstly, persistence of elevated BP between ages 5 and 18 was estimated from sex, anthropometry and BP measurements. Secondly, the association between socio-economic status (SES) change between infancy and adolescence computed from physical household assets and BP at 18 years of age was evaluated using multivariable analyses. Finally, longitudinal BP trajectories were identified using group-based trajectory modeling and multinomial models were used to assess the association of BW, RWG and RHG, and BP trajectories adjusted for several covariates.
Results
The prevalence of hypertension ranged between 8.4 to 24.4% and risk of maintaining the elevated BP status was almost 2-fold between ages 5 and 18 years: RRR: 1.60(95%CI: 1.29-
2.00). An upward social mobility was associated with a 5mmHg reduction in SBP (β: -4.85, 95%CI: - 8.22 - -1.48). Three distinct early patterns of BP development called trajectory groups were identified for SBP and diastolic BP (DBP) for each sex; namely: “lower”, “middle” and “upper.” A kilogram increase in birth weight (BW) reduced the odds of being in the middle compared to lower SBP trajectory (OR: 0.75, 95%CI: 0.58-0.96), while RWG in infancy was associated with a 4-fold increased odds of being in the upper vs lower SBP trajectory for boys (OR: 4.11, 95%CI: 1.25-13.51). In girls, relative weight gain (RWG) (OR: 1.63, 95%CI: 1.08-2.46; 1.77(1.22-2.56)) and relative height gain (RHG) (OR: 1.90, 95%CI: 1.27-2.86; 2.12(1.39-3.23)) in infancy and mid-childhood was associated with almost 2-fold increase in odds of being in the upper vs lower trajectory. The middle SBP trajectory in girls was predicted by RWG (OR: 1.33, 95%CI: 1.00-1.76) and RHG (OR: 1.58, 95%CI: 1.15-2.17) in infancy. DBP trajectories were significantly but inconsistently associated with RWG and RHG for boys and RWG in mid-childhood and infancy in girls for the middle and upper trajectories.
Conclusions
Distinct BP trajectories are established in childhood and persist into early adulthood. Improving SES throughout childhood may have a protective effect on BP. Policy recommendations around early identification of children with elevated BP accompanied by interventions targeted at optimal growth and interrupting the atypical BP trajectories may reduce the burden of disease attributed to hypertension, especially in girls.
Description
A thesis
Submitted to the Faculty of Health Sciences, University of Witwatersrand, in fulfilment of the requirements for the degree of
Doctor of Philosophy
Johannesburg, South Africa
2016