Association of weight-adjusted waist index and lung function in children and adolescents: A cross-sectional study from National Health and Nutrition Examination Survey (NHANES) 2007–2012

The negative impact of obesity on respiratory health has garnered widespread attention. As a novel obesity indicator, the weight-adjusted waist index (WWI) is the focus of our study, which aims to investigate the association between WWI and pulmonary function in U.S. children and adolescents. This cross-sectional study utilized data from the National Health and Nutrition Examination Survey spanning 2007 to 2012, focusing on participants with complete records of both WWI which is computed by dividing waist circumference by the square root of body weight. and pulmonary function measurements like forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC ratio, peak expiratory flow, and forced expiratory flow at 25% to 75% of FVC (FEF25%-75%). Multivariable regression and logistic regression analyses were conducted to assess the independent association between WWI and pulmonary function. Subgroup analyses and interaction tests were additionally performed. The study enrolled a total of 4237 participants. Those in higher WWI quartiles consistently demonstrated poorer pulmonary function metrics. In fully adjusted models, significant inverse associations were observed between WWI and multiple pulmonary function parameters, including FVC (β = -204.29, 95% CI: -231.79 to -176.80), FEV1 (β = -207.14, 95% CI: -230.78 to -183.51), FEV1/FVC ratio (β = -0.01, 95% CI: -0.01 to -0.01), peak expiratory flow (β = -430.92, 95% CI: -488.86 to -372.97), and forced expiratory flow at 25% to 75% of FVC (β = -252.78, 95% CI: -292.93 to -212.64). Participants in the highest WWI quartile exhibited significantly worse pulmonary function compared to those in the lowest quartile (P for trend < .05). Subgroup analyses and interaction tests revealed stronger associations between WWI and pulmonary function impairment in male participants, non-Hispanic Whites, and individuals younger than 15 years. Our research indicates that higher WWI is associated with lower pulmonary function in children and adolescents, highlighting the importance of incorporating central obesity indicators into pediatric health assessments.