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