The evidence linking sex hormones and asthma continues to grow, thanks to research funded by a grant from the National Heart, Lung, and Blood Institute for Joe Zein, MD, staff in the Respiratory Institute. His latest research, presented at the 2018 American Thoracic Society International Conference, shows that oral contraceptive use and endometriosis are associated with a higher risk of lifetime asthma in women of reproductive age.
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Dr. Zein was awarded the grant to study sex differences in severe asthma across the lifespan. His earlier research found that lower testosterone and progesterone levels and higher estradiol levels are associated with reduced lung function in both men and women with severe asthma.
In general, asthma is more prevalent in males 4 to 14 years compared to females (11.5 vs. 9.9 percent), but after puberty, it becomes more prevalent and severe in women. Interestingly, another sex-based reversal seems to occur with menopause, when asthma becomes once again more severe in older male adults. Dr. Zein’s research also demonstrated for the first time that menopause may have a protective factor in the severity of asthma for women.
While the mechanisms are not fully understood, sex hormones have a wide variety of effects on the lungs. Progesterone receptors are expressed in airway epithelium and inhibit ciliary beat frequency, which may impact mucociliary clearance.
Dr. Zein and his team found in a study of 3,272,020 women (20-40 years of age) in a national database that asthma was more prevalent in women with endometriosis (23.8 vs. 13.2 percent, P < 0.001) across weight groups and categories. They replicated those results using the National Health and Nutrition Examination Survey.
“Our epidemiological studies continue to support a link between sex, sex hormones and asthma,” says Dr. Zein. “This finding is further confirmation of our efforts to pinpoint the linking mechanisms so that we can one day develop appropriate treatments.”
In a study of 6,524,990 women (20-50 years of age) in a national database, asthma was more prevalent in women taking OCs (14.3 vs. 8.8 percent, P < 0.001) after adjusting for race, BMI, smoking status and age.
“This database analysis further supports our exploration of the role of sex hormones in asthma pathophysiology,” says Dr. Zein. “Until we discern the exact linking mechanisms, this research can allow sex and factors impacting sex hormones to inform our treatment decisions for women with asthma.”