In adults in the United States, sex hormones play a role in gender differences in asthma, and obesity modifies the effects of these hormones, according to a study published in the American Journal of Respiratory and Critical Care Medicine. Elevated levels of free testosterone in serum are associated with reduced odds of asthma in women, elevated levels of serum estradiol are associated with reduced odds of asthma in nonobese men, and elevated levels of both estradiol and free testosterone are associated with reduced odds of asthma in obese women.

Asthma prevalence is higher among women than men, and the current study was designed to assess whether sex hormone levels play a role in sex differences in asthma. Data were taken from the 2013 to 2014 and 2015 to 2016 study cycles of the US National Health and Nutrition Examination Survey, which is a cross-sectional nationwide survey designed to assess health and nutrition, in which ethnic minorities (Hispanics, non-Hispanic Asians, and non-Hispanic blacks), low-income whites, and persons aged over 80 years are oversampled to increase statistical power for data analysis in these groups. Participants analyzed for this cross-sectional study (N=7615 adults; aged 18-79 years; 3953 men, 3662 women) had both serum levels of estradiol and free testosterone available as well as current asthma status. Multivariate analysis of sex hormones (divided into 4 quartiles) was performed separately in women and men using logistic regression to test for an interaction between obesity and sex hormones on current asthma.

Free testosterone levels in women without asthma were significantly higher than in those with current asthma. In a model unadjusted for serum estradiol level, women whose levels of free testosterone were in the 4th quartile compared with the 1st quartile had 30% to 45% lower odds of current asthma (odds ratio [OR], 0.56; 95% CI, 0.39-0.80). In a model unadjusted for serum free testosterone levels, women with serum estradiol levels in the 3rd quartile compared with the 1st quartile had 34% lower odds of current asthma. After analysis was stratified by obesity, in quartile 4 compared with quartile 1, elevated levels of free testosterone and estradiol in obese women were associated with lowered odds of current asthma (OR, 0.59; 95% CI, 0.37-0.91; and OR, 0.43; 95% CI, 0.23-0.78, respectively), and elevated serum estradiol levels in nonobese men were associated with reduced odds of current asthma (OR, 0.44; 95% CI, 0.21-0.90).

Study limitations included an inability to examine temporal relationships, the lack of data on menopause status and potential confounders, potential misclassification or recall bias, and potential selection bias.


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However, study investigators concluded, “In summary, we found that elevated serum levels of both free testosterone and estradiol were significantly associated with reduced odds of asthma in obese women, and that elevated levels of serum estradiol were significantly associated with reduced odds of asthma in non-obese men. Our findings further suggest that sex steroid hormones play a role in known gender differences in asthma among adults.”

Disclosure: One study author declared an affiliation with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Han YY, Forno E, Celedón JC. Sex steroid hormones and asthma in a nationwide study of U.S. adults [published online September 16, 2019]. Am J Respir Crit Care Med. doi: 10.1164/rccm.201905-0996OC