Association of High Normal Body Weight in Youths With Risk of Hypertension

IMPORTANCE: Ample evidence links obesity to hypertension in youths. However, the association of high normal body mass index (BMI) with obesity and the interaction with different weight trajectories are not well understood. OBJECTIVE: To examine the hypertension risk associated with high normal BMI for age and different weight trajectories in youths. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study assessed 801 019 youths aged 3 to 17 years in an integrated health care system in Southern California from January 1, 2008, to February 28, 2015, with a maximum follow-up of 5 years from January 1, 2008, to February 28, 2020. Data analysis was performed from 2018 to 2022. EXPOSURES: Youths were compared by first available (baseline) sex-specific BMI for age and change in the distance to the median BMI for age during the 5-year follow-up. MAIN OUTCOMES AND MEASURES: Cox proportional hazards regression models with age as a time scale to assess hypertension risk (based on 2017 Blood Pressure Guidelines by the American Academy of Pediatrics from 3 consecutive independent visits), adjusted for sex, race and ethnicity, socioeconomic status, baseline year, and birth year. RESULTS: A total of 801 019 youths (mean [SD] age, 9.4 [4.6] years; 409 167 [51.1%] female]; 59 399 [7.4%] Asian and Pacific Islanders, 65 712 [8.2%] Black, and 427 492 [53.4%] Hispanic) were studied. Compared with youths with a baseline BMI for age in the 40th to 59th percentiles, the adjusted hazard ratio (aHR) for hypertension within a maximum of 5 years was 1.26 (95% CI, 1.20-1.33) for youths between the 60th and 84th percentiles if they maintained their BMI for age. With every 1-unit annual increase in the distance to the median BMI for age, the aHR increased by 1.04 (95% CI, 1.04-1.05). The aHR was 4.94 (95% CI, 4.72-5.18) in youths with a baseline BMI for age in the 97th percentile or higher who maintained their body weight. Weight gain increased the risk associated with baseline BMI for age in the 97th percentile or higher with an aHR of 1.04 (95% CI, 1.04-1.05) per 1-unit annual increase in the distance to the median BMI for age. The risk associated with weight change was higher in youths living with low to high normal weight and overweight than in youths living with severe obesity. CONCLUSIONS AND RELEVANCE: In this cohort study of youths, high normal body weight above the 60th percentile of BMI for age was associated with increased risk of hypertension. Weight gain was associated with further increases in hypertension risk. Further research is needed to evaluate the wide range of body weight considered normal in youths and the health risks associated with high normal weight.