For many years, it has been known that asthma rates in children do not differ much between boys and girls, but in adults, asthma occurs more frequently in women than in men. The reasons for this gender difference are not completely understood, although some hypothesize that it is related to lung function or hormonal differences that vary by sex. In a recent paper, we used data corresponding to more than one million adults from two large CDC-led epidemiological studies (i.e., BRFSS and NHANES) to find out whether demographic factors are associated differently with asthma among men and women. We found that obese women had a much higher prevalence of asthma than men, as this plot of BRFSS results shows:
Similarly, smoking was history was associated with higher asthma prevalence in women than in men:
In quantitative terms, asthma prevalence among grade 2 obese and grade 3 obese vs. not overweight or obese women was 2.5 and 3.5 times higher, respectively, while that in men was 1.7 and 2.4 times higher. For smoking, asthma prevalence among current vs. never smoker women was 1.4 times higher, while that in men was 1.1 times higher. We obtained similar results with NHANES data: asthma prevalence among grade 2 obese and grade 3 obese vs. not overweight or obese respondents was 2.0 and 3.3 times higher for women, though there was no significant difference for men; asthma prevalence among current vs. never smokers was 1.8 times higher for women and not significantly different in men.
Consistent with previous studies, we found that asthma prevalence was higher among those with lower income. This prevalence-by-income effect did not differ considerably between men and women. Disparities of asthma prevalence by race/ethnicity are also a known problem in the U.S. While we observed that black and American Indians/Alaskan Native individuals had increased odds of asthma relative to white individuals in unadjusted analyses, after adjusting for other factors, the association with black race/ethnicity was not significant in males and led to decreased odds of asthma in females, while the association with American Indians/Alaskan Natives was considerably decreased in magnitude in both men and women. We observed decreased asthma prevalence among Asian/Pacific Islander and Hispanic individuals relative to white that differed in magnitude by gender.
As we worked on this paper, we created an app to visualize county-level characteristics of respondents based on BRFSS data used in the analysis. You can use the app to check some asthma statistics for your own county at http://asthmamaps.org.
To reduce asthma prevalence in adults overall, studies should continue to focus on identifying functional mechanisms by which women disproportionately develop asthma and on designing interventions that effectively reduce obesity and smoking.