Early BMI-associated increases in central and peripheral blood pressure in primary school children: evidence of a continuous, nonlinear relationship below the overweight threshold.

Childhood overweight is associated with elevated blood pressure (BP) and future cardiovascular risk. We aimed to determine the body mass index percentile (BMIp) at which blood pressure (BP) begins to increase in children, particularly below the overweight threshold. Central BP may provide additional insight into early hemodynamic changes. In a cohort of primary school children, peripheral and central BP were measured using standardized protocols. Associations of BMIp with BP were evaluated using spline and linear regression models adjusted for age, sex, and height. BMIp categories were used to identify thresholds at which BP was significantly higher than in children with BMIp < 50. Among 1,183 children (mean age 7.9 years), BP increased progressively with rising BMIp, with the greatest elevations in children with overweight or obesity. Significant increases in peripheral and central systolic BP were observed at BMIp levels below the WHO-defined cutoff for overweight, central BP increased at lower BMIp than peripheral BP. Although peripheral diastolic BP was not associated with BMIp, central diastolic BP increased significantly across higher BMIp ranges. Conclusions: In primary school children, BMI-associated increases in BP are detectable at substantially lower BMIp than commonly considered, reflecting a continuous nonlinear relationship. Both peripheral and central BP increased within the high-normal BMI-range. Central BP identified early, distinct BP alterations, including significant diastolic changes not detected with peripheral BP. These findings suggest that cardiovascular risk related to body weight arises along a continuum and support the potential value of early BP monitoring in children with increasing BMI.Trial registration: Trial Registration Number: NCT04942431. Date of Registration: 08.04.2021. What is Known • Childhood overweight is associated with elevated blood pressure, both are key risk factors for future cardiovascular disease. • However, the body mass index level at which blood pressure begins to rise in children remains unclear. What is New • We identify specific body mass index ranges at which blood pressure increased significantly, highlighting children with high-normal body weight as a group at early cardiovascular risk.