Asthma and Asthma Symptoms Associated with Endometriosis and Dysmenorrhea in a Nordic-Baltic Population

Background: Endometriosis, dysmenorrhea, and respiratory symptoms affect large numbers of women. A possible association between asthma and endometriosis has been suggested; however, this relationship is unclear. Dysmenorrhea is very common, and potential associations with asthma symptoms are not known. Aim: To study asthma symptoms associated with endometriosis and dysmenorrhea in women. Methods: We used data from the main and women's questionnaires of the Respiratory Health in Northern Europe study, which included data from women (aged 39-65 years) from Aarhus, Gothenburg, Umeå, Uppsala, Reykjavik, Tartu, and Bergen. Current asthma status was defined by asthma medication usage or asthma attacks in the past 12 months. Asthma symptoms were defined as having ≥3 asthma symptoms in the last 12 months. The data were analyzed using logistic regressions adjusted for age, body mass index, and smoking status. Results: Among 4778 study participants, 201 had endometriosis, and 2154 had dysmenorrhea. Current asthma and asthma symptoms were reported by 14.9% and 12.9%, respectively, of women with endometriosis compared with 9.1% and 9.2%, respectively, of women without endometriosis. The associations of current asthma and asthma symptoms with endometriosis were statistically significant (odds ratio [OR]: 1.87, 95% confidence interval [CI]: 1.25-2.81; and OR: 1.56, 95% CI: 1.01-2.39, respectively). Similar associations were found for dysmenorrhea (current asthma: OR: 1.48, 95% CI: 1.21-1.81; ≥3 asthma symptoms: OR: 1.61, 95% CI: 1.31-1.97). Conclusion: Our study revealed that asthma symptoms were associated with both endometriosis and dysmenorrhea. The associations with dysmenorrhea, which affects a large proportion of women, were almost as strong as the associations with diagnosed endometriosis.