Racial Differences in Rates of Change of Childhood Body Mass Index and Blood Pressure Percentiles

Objective: To assess whether racial differences in rates of change in body mass index (BMI) and blood pressure (BP) percentiles emerge during distinct periods of childhood. Study design: In this retrospective cohort study, we included children aged 5-20 years who received regular outpatient care at a large academic medical center between January 1996 and April 2016. BMI was expressed as age- and sex-specific percentiles and BP as age-, sex-, and height-specific percentiles. Linear mixed models incorporating linear spline functions with 2 breakpoints at 9 and 12 years of age were used to estimate the changes in BMI and BP percentiles over time during age periods: <9, 9-<12, and >12 years of age. Results: Among 5703 children (24.8% black, 10.1% Hispanic), Hispanic females had an increased rate of change in BMI percentile per year relative to white females during ages 5-9 years (+2.94%; 95% CI, 0.24-5.64; P =.033). Black and Hispanic males also had an increased rate of change in BMI percentile per year relative to white males that occurred from ages 5-9 (+2.35% [95% CI, 0.76-3.94; P =.004]; +2.63% [95% CI, 0.31-4.95; P =.026], respectively). There were no significant racial differences in the rate of change of BP percentiles, although black females had higher hypertension rates compared with white females (10.0% vs 5.7%; P <.001). Conclusions: Childhood patterns in BMI percentiles differ by race. Racial differences in rates of change in BMI percentile emerge early in childhood. Further study of early patterns could help to identify critical periods during childhood where disparities begin to emerge.