Published online: June 8, 2020
Intriguing sex-related differences have been long observed in asthma. Asthma, more common in boys than in girls during childhood, becomes more common and more severe in women than in men starting from puberty and throughout adulthood. For several decades, scientists have suggested that the predominance of asthma in women than in men may partly be due to increase in activities of female sex hormones. Consequently, it has been suggested that the use of hormonal contraceptives to suppress the activities of the sex hormones may lead to lower risk of asthma in women. However, studies investigating this topic have so far provided conflicting findings.
In an article recently published in The Journal of Allergy & Clinical Immunology (JACI), Nwaru and colleagues used a large primary care database comprising more than 500,000 women across the United Kingdom to study whether the use of hormonal contraceptives influences the development of asthma in reproductive age women. The women (aged 16-45 years) included in the study were followed for 17 years starting from January 1, 2000 to December 31, 2016. This resulted in 3,597,146-person-years of follow-up during which 25,288 women developed asthma. The use of hormonal contraceptives was defined as: (1) use of any contraceptives versus non-use; (2) use of types of hormonal contraceptives (i.e. combined contraceptives and progestogen-only contraceptives) versus non-use; and (3) duration of use of hormonal contraceptives. In the analyses, the authors adjusted for several factors that might confound the association between hormonal contraceptives and asthma risk, including several indications for the use of hormonal contraceptives.
The authors found that women who used hormonal contraceptives, whether in the past or currently, had significantly lower risk of developing asthma than women who did not use. The results were similar for use of any hormonal contraceptives and each type of hormonal contraceptives. They also found that the beneficial role of hormonal contraceptives was greater for longer duration of use than for shorter duration of use: contraceptive use for five years and more conferred more protection than use for 3-4 years, while use for 3-4 years conferred more protection than use for 1-2 years. The authors suggested that studies investigating the biology underlying these findings are required. They also suggested that it might be helpful to confirm these results through a clinical trial that will investigate whether use of hormonal contraceptives is safe and effective for preventing asthma.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.