Hormonal Contraceptives Are Associated With an Increase in Incidence of Asthma in Women

The purpose of the study was to determine if there is an association between the use of hormonal contraceptives (HC) and incidence of asthma in young woman.This study was conducted in Denmark using data from Danish National Patient Register. All women ages 10 to 40 without asthma who were first time users of hormonal contraceptives from January 1, 2008 to December 31, 2017 were included as cases and nonusers as controls.The study was an exposure-density matched cohort study with each HC user being matched with 5 women with no history of asthma or HC use born the same year. Analysis considered the form of HC (eg, combined HC versus progestin only; IUD versus oral pills). Income, region of living, and urbanization were accounted for, and the Aalen Johansen estimator was used to estimate cumulative risk in the 3 years after HC initiation. Diagnosis of asthma was defined as having filled 2 prescriptions of inhaled corticosteroids in 2 years.There was a total of 184 046 women, 30 669 of whom were started on HC. The average age of HC initiation was 15.6 years. Women who were treated with HC of any form were more likely to initiate treatment of asthma with a cumulative risk of 2.7% versus 1.5% in non HC users. Younger women who initiated HC between 10 and 13 years of age had even greater association with a risk of 3.6% versus 1.6% in nonusers. Additionally, the risk for users between age 14 and 18 was 2.7% versus 1.5% in nonusers. The risk for women over 18 years of age was not statistically significant with risk being 1.1% in users versus 0.9% in nonusers. The risk was statistically significant for second and third generation combined pills but not for fourth generation combined pills or hormonal IUDs.The initiation of hormonal contraceptives is associated with the development of asthma in young women less than 18 years of age. Some forms of HC were more strongly associated with asthma than others, including second and third generation combined oral pills and progestin only oral pills.HCs are used widely by adolescents. There are several factors that help determine which HC is chosen for each patient, including personal and family history, adherence, and cost. This study indicates that risk of developing asthma should also be considered when initiating HC in this patient population, especially in younger patients. However, the risk, even with the options with the strongest associations, remains low overall. Of note, this study was conducted in Denmark and may not be as generalizable to the American patient population.