Mortality in Patients with Polymyositis and Dermatomyositis in an Israeli Population

The reported mortality rates of patients with polymyositis and dermatomyositis are highly variable worldwide. The excess mortality of patients with polymyositis/dermatomyositis has not been evaluated in an Israeli population.

To investigate the overall mortality in a large and well-established cohort of patients with polymyositis/dermatomyositis as compared to the mortality expected in the matched general population in a tertiary medical center.

In this retrospective cohort study, the mortality of 166 patients with polymyositis/dermatomyositis was compared to age- and sex-matched control subjects in the general population. All-cause standardized mortality ratios (SMRs) were estimated.

Overall, 47 (28.3%) deaths were observed among patients with polymyositis/dermatomyositis during a mean follow-up period of 5.8 ± 4.8 years, which was 7 times higher than in the control group (SMR 7.4, 95% confidence interval [95%CI] 5.5-9.8). The SMRs were comparable in patents with polymyositis (7.7, 95%CI 4.8-12.3) and dermatomyositis (7.2, 95%CI 5.0-10.3). The 1-, 5-, 10-, and 15-year overall survival rates were 90.0%, 82.8%, 51.5%, and 26.1%, respectively, in patients with polymyositis, and 80.3%, 59.6%, 40.0%, and 17.1%, respectively, in patients with dermatomyositis.

The overall mortality among Israeli patients with polymyositis/dermatomyositis is 7.4 times greater than for the general population. Although long-term mortality was comparable between patients with dermatomyositis and polymyositis, patients in the former group died at a notably earlier stage.