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To investigate whether variations in growth patterns in early-life are associated with blood pressure at age 6.5 years by modelling detailed, individual growth trajectories between birth and 5 years of age.
Prospective cohort study nested in a large randomised trial.
10 494 children from Belarus who were born in one of 31 hospitals that participated in a cluster randomised trial of breastfeeding promotion intervention and had multiple measures of height and weight from birth to age 6.5 years. We analysed all 13 childhood growth measurements to develop a best-fitting linear spline random-effects model with 2 knots (thus dividing follow-up into 3 time periods, each with its own trajectory). The spline models were used to generate 4 random effects coefficients: birthweight; “early infant weight velocity” (birth–3 mo); “late infant weight velocity” (3 mo–1 yr) and “childhood weight velocity” (1–5 yrs). Each coefficient denotes an individual’s deviance from average birthweight or velocity at each time period; together, the coefficients are a within-subject summary of each child’s growth curve from birth to 5 years. The coefficients were converted into age-standardised z-scores to render them directly comparable.
Main Outcome Measures
Systolic and diastolic blood pressure (mm Hg) measured at age 6.5 years. Sex-specific OLS was used to investigate associations of each coefficient with blood pressure, controlled for hospital and baseline confounders.
Birth-weight and weight velocity at all 3 time-periods were positively associated with blood pressure in boys. The change in systolic blood pressure per z-score increase in growth was 0.27 (95% CI 0.07 to 0.47) for birthweight; 0.47 (0.26 to 0.68) for “early infant weight velocity”; 0.70 (0.50 to 0.90) for “late infant weight velocity” and 0.96 (0.76 to 1.16) for “childhood weight velocity”. Associations were similar for girls (all p-values for interactions >0.1.).
Children’s growth trajectory between birth and 5 years was positively associated with blood pressure at age 6.5 years. Associations increased in magnitude with age. Further analysis will investigate whether early or late infant growth have any additional influence on blood pressure levels in childhood, over and above weight at 6.5 years.