Sarcoidosis incidence and prevalence: a nationwide register-based assessment in Sweden

Our objective was to estimate the contemporary incidence and prevalence of sarcoidosis using Swedish population-based register data. Adults with any sarcoidosis-coded visit were identified from the National Patient Register (hospitalisations 1964-2013 and outpatient care 2001-2013). Demographic and medication dispensing data were retrieved from national registers. We estimated the prevalence of sarcoidosis in 2013 overall and by county of residence. The incidence of sarcoidosis during 2003-2012 was estimated by sex, age, education level and year of diagnosis. Case definitions were varied to test their robustness. More than 16000 individuals had a history of sarcoidosis in 2013. When defined as two or more sarcoidosis-coded visits, the prevalence was 160 per 100 000. Using different definitions, the prevalence ranged from 152 (requiring a specialist visit) to 215 per 100 000 (only one visit required). The highest prevalence was observed in northern less densely populated counties. The incidence was 11.5 per 100 000 per year and varied by -10% to +30% depending on case definition. The incidence peaked in males aged 30-50 years and in females aged 50-60 years, but did not differ by education level and was stable over time. This study represents the largest epidemiological investigation of sarcoidosis using population-based individual-level data. Age at diagnosis in men was 10 years younger than in women and geographical variation was observed.