It is well established that obesity is associated with an increased risk of elevated and high blood pressure (BP) in children and adolescents. However, it is uncertain whether there is an increase in the risk of elevated and high BP associated with an increase of body mass index (BMI) among children and adolescents whose BMI is in the accepted normal range. Data were available for 58 899 children and adolescents aged 6–17 years from seven national cross-sectional surveys in China, India, Iran, Korea, Poland, Tunisia, and the United States. The subjects were divided into eight percentile subgroups according to their BMI levels based on the World Health Organization recommendations. Elevated BP and high BP were defined using the 2016 international child BP criteria. Compared with the reference subgroup of the 5th–24th percentiles, the odds ratios (ORs) for high BP were 1.27 (95% confidence interval [CI], 1.14–1.41; P < 0.001) in the 25th–49th percentile subgroup, 1.55 (95% CI, 1.39–1.73; P < 0.001) in the 50th–74th percentile subgroup, and 2.17 (95% CI, 1.92–2.46; P < 0.001) in the 75th–84th percentile subgroup, respectively, after adjustment for sex, age, race/ethnicity, height and country. Additionally, the corresponding ORs for elevated BP were 1.21 (95% CI, 1.10–1.32; P < 0.001), 1.55 (95% CI, 1.42–1.69; P < 0.001), and 1.80 (95% CI, 1.62–2.01; P < 0.001), respectively. In conclusion, a BMI in the 25th–84th percentiles, within the accepted normal weight range, was associated with an increased risk of elevated and high BP among children and adolescents. It is important for children and adolescents to keep a BMI at a low level in order to prevent and control hypertension.
