Central obesity and blood pressure burden among Chinese children and adolescents with normal body mass index: a repeated-measures analysis of the China health and nutrition survey

Objective Body mass index (BMI) is widely used to screen for pediatric adiposity, but it cannot differentiate fat distribution and fails to identify central fat accumulation among normal-weight youth. We aimed to evaluate whether central obesity was independently associated with high blood pressure among Chinese children and adolescents with normal BMI. Methods We analyzed repeated examination data from 4,841 Chinese children and adolescents aged 7–17 years (7,192 complete-case observations) with normal BMI from the China Health and Nutrition Survey (1993–2011). Central obesity was defined as a waist-to-height ratio (WHtR) ≥ 0.50. The primary outcomes were above-normal blood pressure and high blood pressure at survey examination, classified using age-, sex-, and height-specific Chinese references. Population-average associations were estimated using generalized estimating equations (GEE) with robust standard errors. Standardized absolute risks, robustness checks, subgroup analyses, and exploratory longitudinal analyses were also performed. Results Central obesity was present in 4.3% (323/7,469) of normal-BMI person-wave observations. In fully adjusted models, central obesity was associated with significantly higher odds of above-normal blood pressure (OR 1.43, 95% CI: 1.07–1.90; p = 0.016) and high blood pressure (OR 1.54, 95% CI: 1.07–2.21; p = 0.022). Standardized absolute risk differences were 5.1 and 3.5 percentage points, respectively. Sensitivity and subgroup associations were generally consistent across sex, urbanicity, and survey period. Exploratory longitudinal analyses (lagged, transition, and trajectory models) were directionally compatible with the primary findings but limited by sparse exposed observations. Conclusion Among Chinese children and adolescents with normal BMI, central obesity was associated with a higher burden of blood pressure. Waist-based anthropometric assessment may complement BMI in identifying normal-weight youth with an unfavorable blood pressure profile, warranting confirmation in contemporary pediatric cohorts.