Risk of chronic spontaneous urticaria in reproductive‐aged women with abnormal uterine bleeding: A population‐based cohort study

Women with abnormal uterine bleeding (AUB) have been reported to develop chronic spontaneous urticaria (CSU). Nevertheless, whether or not AUB women have an increased risk of CSU has not been examined in large-scale epidemiologic studies. This study aimed to investigate the risk of CSU among reproductive-aged women with AUB. A total of 79 595 patients and 79 107 propensity-score matched controls were recruited from Taiwan's National Health Insurance Research Database to conduct a nationwide cohort study. The Cox proportional-hazard regression model was applied to examine the adjusted hazard ratios (aHR) and 95% confidence intervals (CI) for CSU in relation to AUB. We found that women with AUB had a higher risk for CSU (aHR = 1.83; 95% CI, 1.76-1.90) than women without AUB. Subgroup analyses revealed that AUB with an abnormal bleeding frequency (aHR = 1.70; 95% CI, 1.60-1.79), irregular bleeding (aHR = 1.80; 95% CI, 1.71-1.89), and intermenstrual bleeding (aHR = 1.65; 95% CI, 1.49-1.83) were associated with an increased risk of CSU compared with those without abnormalities. The Kaplan-Meier analysis revealed that the cumulative incidence of developing CSU was consistently higher in the AUB cohort than in the non-AUB cohort during the entire follow-up period (log-rank test, p