possibly explaining in part the different prevalence of asthma in men and women, according to the findings of a large cross-sectional population based study.
Yueh-Ying Han, PhD, of the Children’s Hospital of Pittsburgh and colleagues investigated the role of free testosterone and estradiol levels and current asthma among adults. The impact of obesity on that association was also examined. The investigators analyzed data from 7,615 adults (3,953 men and 3,662 women) who participated in the 2013-2014 and 2015-2016 U.S. National Health and Nutrition Examination Survey. The data included health interviews, examination components, and laboratory tests on each patient. Serum samples were analyzed by the division of laboratory sciences of the Centers for Disease Control and Prevention. Logistic regression was used for the multivariable analysis of sex hormone levels (as quartiles) and current asthma, and the analysis was done separately on men and women. Pregnant women were excluded, in addition to individuals with incomplete data. The exclusions tended to be Hispanic, former smokers, lower income, and lacking private insurance. The overall prevalence of current asthma in the sample was 9% (6% in men and 13% in women).
Three models were generated based on serum levels in women and in men.
For model 1 (unadjusted for estradiol), women whose serum testosterone levels were in the second and fourth quartiles had 30%-45% significantly lower odds of having current asthma than those whose serum testosterone level was in the lowest quartile. Among men, those whose serum testosterone levels were in the second and fourth quartiles had 12%-13% lower odds for current asthma.
For model 2 (unadjusted for free testosterone), women whose serum estradiol levels were in the third quartile had 34% significantly lower odds of having current asthma than those whose estradiol levels were in the lowest quartile. The findings were similar for men, that is, those whose serum estradiol levels were in the third quartile had 30% lower odds for having asthma, compared with those with in the lowest quartile.
For model 3 (a multivariable model including serum levels of both estradiol and free testosterone), women whose serum testosterone levels were in the second and fourth quartiles had 30% and 44% lower odds of current asthma than those whose serum testosterone levels were in the lowest quartile. But in this multivariable model, the association between serum estradiol and current asthma was not significant. Among men (models 1-3), the magnitude of the estimated effect of serum testosterone and serum estradiol on current asthma was similar to that observed in female participants, but neither serum testosterone nor serum estradiol was significantly associated with current asthma.
The investigators then analyzed the impact of obesity on the relationship between serum hormone levels and obesity. Obesity was defined as body mass index equal to or greater than 30 kg/m2. A total of 1,370 men and 1,653 women were included in this analysis. In multivariable analyses of the obese participants, adjustment without (model 1) and with (model 3) serum estradiol, serum free-testosterone levels in the highest (fourth) quartile were significantly associated with reduced odds of asthma in obese women. In multivariable analyses without (model 2) and with (model 3), serum estradiol levels above the first quartile were significantly associated with reduced odds of current asthma in obese women.
In contrast to the results in obese women, neither serum free testosterone nor serum estradiol was significantly associated with current asthma in obese men or nonobese women.
Dr. Han and coauthors suggested a possible mechanism of the role of sex hormones in asthma. “Androgens such as testosterone may reduce innate and adaptive immune responses, while estrogen and progesterone may enhance T-helper cell type 2 allergic airway inflammation.”
They concluded: “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 nonobese men. Our findings further suggest that sex steroid hormones play a role in known sex differences in asthma among adults.”
One coauthor has received research materials from Merck and GlaxoSmithKline (inhaled steroids), as well as Pharmavite (vitamin D and placebo capsules), to provide medications free of cost to participants in National Institutes for Health–funded studies, unrelated to the current work. The other authors reported no conflicts of interest.
SOURCE: Han Y-Y et al. J Respir Crit Care Med. 2019 Sep 16. doi: 10.1164/rccm.201905-0996OC.