Sex differential association of dermatomyositis with Sjögren syndrome

BACKGROUND: Although dermatomyositis and Sjogren syndrome share serologic autoantibodies and genetic polymorphisms, population data about the incidence of Sjogren syndrome in patients with dermatomyositis is unavailable. We performed a nationwide cohort study to explore the potential relation between dermatomyositis and Sjogren syndrome and, if an association exists, to elucidate whether it varies by sex. METHODS: We identified all patients with newly diagnosed dermatomyositis from the Registry of Catastrophic Illness Database in Taiwan between Jan. 1, 1998, and Dec. 31, 2011. Each patient was matched to, at most, 5 control patients from the National Health Insurance Research Database by age, sex and entry date. Cox regression was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) of Sjogren syndrome after adjusting for age, sex, rheumatoid arthritis, systemic lupus erythematosus and systemic sclerosis. RESULTS: A total of 1602 patients with dermatomyositis and 7981 control patients were enrolled in the study. There was a positive association of having Sjogren syndrome among patients with dermatomyositis after adjusting for age, sex, rheumatoid arthritis, systemic lupus erythematosus and systemic sclerosis (HR 2.67, 95% CI 2.01–3.54). The association was more pronounced in the male cohort (HR 2.69, 95% CI 1.19–6.09). INTERPRETATION: We found a sex differential association of Sjogren syndrome among patients with dermatomyositis independent of age and concomitant autoimmune disease. Further studies are required to determine the clinical importance of this association for both outcomes and therapeutic options.