Nonlinear association between body roundness index and asthma in U.S. children and adolescents: a cross-sectional study (NHANES 1999-2023).

Objectives

Body Roundness Index (BRI) is a new measure of central fat distribution linked to asthma risks, but its connection to asthma in children is unclear. This study investigates the relationship between BRI and asthma in U.S. children and adolescents.

Methods

We conducted a cross-sectional study of 32 738 participants aged 3-17 years using National Health and Nutrition Examination Survey (NHANES) data (1999-2023). BRI was calculated from height and waist, and logistic regression estimated the BRI-asthma association, adjusting for age, sex, race/ethnicity, education level, poverty income ratio, physical activity, and passive smoking (serum cotinine).

Results

In the study population, 5609 (17.13%) had asthma. A nonlinear association was observed between BRI and asthma. We identified a critical BRI threshold value of approximately 3.59. For BRI values below 3.59, each unit increase in BRI was associated with higher odds of asthma (OR = 1.25, 95% CI: 1.18-1.32, P < 0.001). In contrast, for BRI values above 3.59, the increase in odds was more modest, yet remained significant (OR = 1.06, 95% CI: 1.02-1.09, P = 0.001). A log-likelihood ratio test confirmed the nonlinear association (P < 0.001).

Conclusions

In this study of U.S. children and adolescents, a higher BRI was associated with a greater risk of having asthma. The relationship was nonlinear, with a pronounced increase in asthma risk at lower BRI levels, while the increase leveled off at higher levels. Given the cross-sectional design, causality cannot be inferred.