The effect of body mass index on blood pressure varies by race among obese children

OBJECTIVE: Previous studies have shown that the effect of adiposity on blood pressure (BP) intensifies as children become increasingly obese. Black children tend to have greater body mass index (BMI) and higher BP than age-matched white children. It is unclear whether the BP effects of BMI are race-specific among black and white children, and data on obese Hispanic children are sparse. We compared the BP effect of BMI in obese white, black, and Hispanic children. METHODS: We examined the medical records of children enrolled in a pediatric obesity clinic. Height, weight, BP, and fasting insulin were assessed as part of routine clinical care. The concurrent effects of age and BMI on BP percentile values were examined using semiparametric regression, which allows the accommodation of nonlinear effects. RESULTS: The study included 873 children (338 male; 354 black, 447 white, 72 Hispanic; 11.7±3.5 years, BMI 36.2±8.5 kg/m2). While BMI Z-scores were similar among the groups, systolic BP (SBP) was higher in black children and Hispanic children (white: 107 mm Hg; black: 112 mm Hg; Hispanic: 112 mm Hg; p=0.0001). Age, sex, and height-adjusted SBP percentiles were significantly different among the three groups (white: 50; black: 59; Hispanic: 59; p=0.0006). In children of the same age, BP was higher at any given BMI in black children and Hispanic children. CONCLUSIONS: Among children referred for treatment of obesity, black children and Hispanic children are at a greater risk for having elevated BP when compared to white children of similar age and BMI.