The association of asthma duration with body mass index and Weight-Adjusted-Waist index in a nationwide study of the U.S. adults

The association between obesity and asthma has been of interest, but whether the duration of asthma has an effect on obesity is still limitedly studied. The purpose of this study was to investigate the association between asthma duration and obesity-related indexes, where obesity-related indexes include Body mass index (BMI) and Weight-adjusted-waist index (WWI). Data from National Health and Nutrition Examination Survey (NHANES) 2009-2018 were obtained to conduct this cross-sectional study. Duration of asthma was used as the independent variable and obesity-related indexes as the response variables. Multiple linear regression was used to assess the association between the independent variable and the response variables, and subsequently smoothed curve fitting and threshold effect analysis were performed to clarify whether there was a nonlinear correlation between the independent variable and the response variables. Finally, subgroup analysis was conducted to find sensitive populations. A total of 9170 participants were included in the analysis. Asthma duration was statistically different between the two groups when all participants were grouped by median WWI (Q1