Purpose: Although prospective data are limited, recent cross-sectional studies support obesity as a cause of asthma. They also suggest that the association is present only among women. Our analysis examines possible sex-race differences in the relationship between obesity and asthma.
Methods: We examined data from the 2000 Behavioral Risk Factor Surveillance System. To minimize diagnostic bias, the sample was limited to adults aged 18 to 34 years. All cases had doctor-diagnosis of asthma and ongoing symptoms. Multiple logistic regression was used to examine risk factors for current asthma vs. never having asthma.
Results: Obesity and asthma were more strongly related among women than men (test for interaction, p<0.01). Across increasing categories of body mass index (BMI), we observed a dose-response relationship among women (odds ratios: 0.9, 1.0 [reference], 1.0, 1.3, 1.5, 1.8, and 3.2) but only a non-significant increased risk in severely obese men (odd ratio: 2.0). In subgroup analyses, however, the obesity-asthma association was present in four of six sex-race/ethnicity subgroups, including black and Hispanic men.
Conclusions: Although the obesity-asthma association is stronger among women than men, our analysis demonstrates a strong positive association among men from minority groups. These race-specific results may help explain some of the "inconsistencies" in prior studies.