Does obesity worsen asthma-related outcomes in US children?

Despite the upward trends in both asthma and obesity in the US, and numerous studies on their possible correlation, an association has not yet been researched in a nationally representative sample of the US pediatric population using standard BMI categories. The novelty of the present study also lies in investigating the interaction effects of sex, age and race on the association between obesity and asthma. This study used data on 6770 children ages 12-17 from the 2008 and 2009 National Health Interview Survey. The independent variables included BMI z-scores and categories, region, sex, age and race, and the outcomes included whether the children ever had asthma, still have asthma, have had an asthma attack in the past 12 months, and have had visit to ER due to asthma in the past 12 months. Logistic regressions were performed to analyze correlations. Obese children, on average, showed greater odds of ever having asthma, still having asthma, and having had an asthma attack in the past 12 months (marginal effects were 7 percentage points, 5 percentage points, and 3 percentage points, respectively) compared to normal-weight children (p<0.001). A robustness check using continuous z-scores showed similar results. Moreover, the effect of obesity on still having asthma was elevated among females as compared to males (average logit interaction effect=.030, s.e.=.015, z=2.17). Our findings suggest that increasing BMI and obesity significantly worsen asthma-related outcomes in US children. In addition, the effect of obesity on the probability of still having asthma is significantly modified by gender.