Epidemiological study of adult-onset Still's disease using a Japanese administrative database.

Adult-onset Still's disease (AOSD) is a rare disease, and large epidemiological studies of this disease are limited. Furthermore, it has been difficult to show the incidence and characteristics of severe AOSD complications due to the rarity of this disease. The aim of our study was to describe the demographics of AOSD and the incidence and characteristics of severe complications. Using a large Japanese administrative database, we identified hospitalized patients with AOSD and described the demographics. We also calculated the incidence of severe complications (i.e., macrophage activation syndrome [MAS] and disseminated intravascular coagulation [DIC]) and in-hospital mortality in AOSD patients, and then analyzed the age-controlled difference between men and women. We identified 513 patients with AOSD (mean age: 53.1 years; women 64.1 %). According to the age distribution, there was no distinct peak age. The thirties and the sixties were relatively large age groups. There were 76 patients of AOSD with MAS or DIC observed in this study. The incidence of severe complications was 14.8 %, 95 % CI [11.9, 18.2]. Women were more likely to have severe complications than men after controlling for age (odds ratio: 2.07; [1.14, 3.73]; p = 0.014). AOSD does not predominantly affect young adults in our study population. Elderly AOSD patients can be observed more than before due to global population aging. Severe complications are more likely to occur in women than in men.