Abstract
We investigated the relationship between morphine treatment and the risk of atrial fibrillation (AF) in female patients with breast cancer. We identified a malignancy cohort of 73,917 female breast cancer patients without an AF history before the date of breast cancer diagnosis between 2000 and 2010 by using the Longitudinal Health Insurance Database for Catastrophic Illness Patients in Taiwan. This malignancy cohort was divided into morphine and comparison cohorts comprising 18,671 and 55,246 patients, respectively, and the incidences of newly diagnosed AF were calculated. We used the Cox proportional hazard model with time-dependent exposure covariates to estimate the risk of AF. The effect of morphine was assessed through multivariable Cox proportional hazard regression controlling for age, the Charlson comorbidity index (CCI) score, and the use of bisphosphonates and paclitaxel. Compared with nonmorphine users, patients who received morphine exhibited a 4.37-fold (95% CI = 3.56-5.36) increase in the risk of developing AF. The risk of AF increased as the CCI score increased, but decreased in patients with tamoxifen treatment. This risk is especially significant in current morphine users of all ages and with low CCI score. AF risk increased as the duration of morphine use lengthened (P for trend <0.0001). The incidence of AF in female breast cancer patients in Taiwan is associated with morphine, but prevented by tamoxifen treatment.