Epidemiology and trends in survival of systemic sclerosis in Olmsted County (1980–2018): A population-based study

Background/Purpose: To update the epidemiology of systemic sclerosis and evaluate the performance of the American College of Rheumatology/European League Against Rheumatism 2013 versus 1980 American Rheumatism Association classification criteria in a US population-based cohort. Methods: An inception cohort of patients with incident systemic sclerosis from 1 January 1980 through 31 December 2018, in Olmsted County, Minnesota, was identified based on comprehensive individual medical record review. Incidence and prevalence rates were age- and sex-adjusted to the 2010 US white population. Survival rates were compared with expected rates in the general population. Fulfillment of 1980 and 2013 classification criteria was ascertained. Results: A total of 85 incident cases of systemic sclerosis (91% female, mean age = 55.4 ± 16 years) and 49 prevalent cases on 1 January 2015 were identified. The overall age- and sex-adjusted annual incidence was 25 (95% confidence interval = 20–31) per million population, with no change in incidence over time. The age- and sex-adjusted prevalence was 436 (95% confidence interval = 313–558) per 1,000,000 population. 77 (91%) patients fulfilled the 2013 classification criteria, and 38 (45%) fulfilled the 1980 criteria. Mortality among patients with systemic sclerosis was significantly higher in comparison to the general population, with a standardized mortality ratio of 2.48 (95% confidence interval = 1.76–3.39) and no evidence of improvement over time. Conclusion: Systemic sclerosis developed in 25 persons/million/year with no change over the 39-year study period. The 2013 classification criteria perform significantly better than the 1980 criteria but failed to classify 9% of patients. Systemic sclerosis portends a 2.5-fold higher risk of mortality than the general population, with no evidence of improved survival over time.