[Association between the trajectory of body mass index and elevated blood pressure in children: a cohort study from...

To characterize the longitudinal trajectories of body-mass-index-for-age Z-score(BAZ) from birth to 7-9 years and to explore their association with elevated blood pressure(EBP) in childhood.

Based on the TAWS prospective cohort study in China, children living in Taicang were followed from 2013 to 2024. Length/height and weight of children were measured at 1, 3, 6, 8 months, and 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7-9 years of age. Blood pressure was measured in 2024 when children were 7-9 years old, and EBP was defined according to Chinese reference of screening for EBP among children. BAZ was calculated based on the World Health Organization child growth standards. Group-based trajectory modeling(GBTM) was applied to identify BAZ trajectories. Multivariate logistic regression was used to assess the association between BAZ trajectories groups and EBP, adjusting for potential confounders.

Among the 1, 274 children included in this study, the prevalence of EBP was 20.6%. GBTM identified three distinct BAZ trajectories: low-decreasing(34.5%), moderate-stable(48.3%), and high-increasing(17.2%). After adjustment for child's gender, initial BAZ, and age at the last follow-up, children in the high-increasing BAZ group had an increased risk of EBP(OR=1.55, 95%CI 1.07-2.23, P=0.02) compared to those in the moderate-stable BAZ group, while the low-decreasing BAZ group showed no statistically significant association with EBP(OR=0.77, 95%CI 0.55-1.06, P=0.11). From 2.5 years old onwards, BAZ values in children with EBP were consistently higher than those with normal blood pressure(P<0.05).

The high-increasing BAZ trajectory from birth to nine years is associated with an increased risk of EBP in children aged 7-9 years. The age of 2.5 years may represent a critical starting point for interventions aimed at controlling BAZ rise to mitigate future EBP.