Association between cardiometabolic index and lung function in US adolescents: A cross-sectional study from the 2007 to 2012 NHANES.

Obesity is a key determinant of pulmonary function. The cardiometabolic index (CMI), which integrates body fat distribution and lipid metabolism status, directly reflects cardiovascular metabolic risk and health status. However, previous studies have not explored its relationship with pulmonary function measurements in adolescents. This cross-sectional study analyzed data from the publicly available 2007 to 2012 cycle of the National Health and Nutrition Examination Survey. Among the pediatric participants, the CMI was the exposure of interest, calculated as (triglycerides [mmol/L]/high-density lipoprotein cholesterol [mmol/L]) × waist-to-height ratio. Pulmonary function outcomes, assessed by spirometry, included forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), the FEV1/FVC ratio, and peak expiratory flow. To verify the robustness of the results, subgroup analyses and interaction tests were additionally performed. Furthermore, smooth curve fitting was applied to characterize any potential nonlinear relationships. The study population comprised 1251 adolescents aged 12 to 19 years. When the model was adjusted for all covariates, multivariable linear regression analysis revealed that each unit increase in Ln-CMI was associated with an increase in FEV1 (β = 129.01; 95% CI: 21.26-236.76), increased FVC (β = 397.76; 95% CI: 275.06-520.45), and a decreased FEV1/FVC ratio (β = -0.03; 95% CI: -0.04 to -0.02). Ln-CMI is positively correlated with FEV1 and FVC, and negatively correlated with FEV1/FVC. Our analysis of large-scale population data confirms a significant association between elevated CMI levels in American adolescents aged 12 to 19 and markedly reduced lung function indicators.