Sex Steroid Hormones and Asthma in a Nationwide Study of U.S. Adults

Rationale Women have a higher burden of asthma than men. Although sex hormones may explain sex differences in asthma, their role is unclear. Objectives To examine sex hormone levels and asthma in adults. Methods Cross-sectional study of serum levels of free testosterone and estradiol and current asthma in 7,615 adults (3,953 men and 3,662 women) aged 18–79 years who participated in the 2013–2014 and 2015–2016 U.S. National Health and Nutrition Examination Survey. Logistic regression was used for the multivariable analysis of sex hormones and current asthma, which was conducted separately in women and men. Measurements and Main Results Free testosterone levels in the fourth quartile were associated with lower odds of current asthma in women (odds ratio [OR] for the fourth quartile [Q4] vs. Q1, 0.56; 95% confidence interval [CI], 0.39–0.80). Given an interaction between obesity and sex hormones on current asthma, we stratified the analysis by obesity. In this analysis, elevated free testosterone (OR for Q4 vs. Q1, 0.59; 95% CI, 0.37–0.91) and estradiol (OR for Q4 vs. Q1, 0.43; 95% CI, 0.23–0.78) levels were associated with reduced odds of current asthma in obese women, and an elevated serum estradiol was associated with lower odds of current asthma in nonobese men (OR for Q4 vs. Q1, 0.44; 95% CI, 0.21–0.90). Conclusions Our findings suggest that sex hormones play a role in known sex differences in asthma in adults. Moreover, our results suggest that obesity modifies the effects of sex hormones on asthma in adults.