Increased Risk of Venous Thromboembolism in Patients with Dermatomyositis/Polymyositis: A Nationwide Cohort Study

Objectives: The number of previous studies on the risk of venous thromboembolism (VTE) in patients with dermatomyositis/polymyositis (DM/PM) is limited. Therefore, we conducted a nationwide retrospective cohort study to investigate the effects of DM/PM on the risk of VTE. Methods: We identified patients with newly diagnosed DM/PM in Taiwan between 2000 and 2010 using the National Health Insurance Research Database (NHIRD) and the Catastrophic Illness Patient Database. Each DM/PM patient was frequency-matched to 4 control patients according to age, sex, and index year. All of the patients were observed from the index date until the occurrence of a VTE event, censor, or until December 31, 2010. We calculated the hazard ratios (HRs) and 95% confidence intervals (CIs) of VTE in the DM/PM and comparison cohorts using the Cox proportional hazards regression model. Results: We followed up with the 2031 DM/PM patients (67.8% women, mean age of 46.1 y) and 8124 control patients for 9987 and 48 081 person-years, respectively. The DM/PM patients exhibited an 11.1-fold increased risk of VTE compared with that of the non-DM/PM comparison cohort after adjusting for age, sex, and comorbidities (95% CI = 5.21-23.6). The older patients with DM/PM exhibited a multiplicative increased risk of VTE development compared with that of the control patients (adjusted HR = 26.8, 95% CI = 8.55-84.2), and the DM/PM patients with any comorbidity showed an additive risk of developing VTE (adjusted HR = 33.3, 95% CI = 11.2-99.4). Conclusion: The risk of VTE is significantly higher in DM/PM patients than in non-DM/PM patients. (C) 2014 Elsevier Ltd. All rights reserved.