Risk of type 2 diabetes mellitus in female breast cancer patients treated with morphine: A retrospective population-based time-dependent cohort study

Aims: We aimed to examine whether morphine treatment is associated with type 2 diabetes mellitus (T2DM) in female breast cancer patients. Methods: We conducted a retrospective cohort analysis of the Longitudinal Health Insurance Database for Catastrophic Illness Patients in Taiwan. A total of 31,112 women with breast cancer without T2DM history during the period 2000-2005 were identified, divided into morphine and non-morphine users (8071 and 23,041 patients, respectively), and the hazard ratios of newly diagnosed T2DM during the period 2005-2010 were calculated. We used a Cox proportional hazard model with time-dependent exposure covariates to estimate the risk of T2DM. The dosage of morphine was counted as defined daily dose and its effect was assessed by multivariable Cox proportional hazard regression controlling age, Charlson comorbidity index, outpatient department visits, antipsychotics, and breast cancer drugs. Results: Morphine users were 1.24 times more likely to suffer from T2DM than non-morphine users (95% CI = 1.04-1.49). Risk increased slightly with the morphine dosage, in patients aged 35-49 years, and with tamoxifen, aromatase inhibitors, and antipsychotics treatment. Conclusions: The incidence of T2DM is associated with morphine treatment in female breast cancer patients. A higher risk was observed in patients aged 35-49 years using higher dose of morphine, and may be increased by tamoxifen and aromatase inhibitors.