Weight-Adjusted Waist Index and Its Association with Pulmonary Function in Children: 6-17 Years: Cross-Sectional Findings

BackgroundExcess adiposity has been linked to compromised lung function and elevated susceptibility to respiratory diseases which may lead to long-term lung deterioration. Conventional indicators of obesity, such as BMI and waist circumference, have limitations due to the so-called "obesity paradox." The Weight-Adjusted Waist Index (WWI) is another way to assess central fat distribution. However, its relationship with lung function in children has not been explored to date. ObjectiveTo explore the correlation between WWI and lung function parameters among children aged 6 to 17. MethodsData from NHANES 2007-2012 were used for cross-sectional analysis. An adjusted multivariate regression framework weighted by the inclusion sample was used to assess the relationship between WWI and pulmonary function indices (FVC, FEV1, FEF25% -75%, PEF, and FEV1/FVC). Possible nonlinear relationship was assessed using curve fitting and split linear regression. Subgroup analyses were performed to assess differences between groups. ResultsThis study involved 3,717 US children. Higher WWI was associated with lower FVC, FEV1, FEV1 25%-75% and PEF ({beta} = -0.28, -0.26, -0.30, -0.30, -0.30, and -0.58). The association between FEV1/FEVC and WWI was nearly significant ({beta} = -0.06, P = 0.054). The breakpoints for nonlinear associations were 10.83, 10.70, 10.70, 11, and 10.79 (P < 0.001). Subgroup analyses showed stronger correlations for boys and L-shaped correlations for boys. ConclusionA nonlinear negative correlation between WWI and respiratory capacity metrics was found in US children, emphasizing the potential relevance of maintaining optimal WWI to respiratory health. Prospective cohort studies are warranted to validate these preliminary observations.