Background/purpose: To update the epidemiology of systemic sclerosis (SSc) and evaluate the performance of the ACR/EULAR 2013 vs. 1980 ARA classification criteria in a U.S. population-based cohort.
Methods: An inception cohort of patients with incident SSc from January 1, 1980, through December 31, 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 SSc (91% female, mean age 55.4 ± 16 y) and 49 prevalent cases on Jan 1, 2015 were identified. The overall age- and sex-adjusted annual incidence was 25 (95% CI 20-31) per million population, with no change in incidence over time. The age- and sex-adjusted prevalence was 436 (95% CI: 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 SSc was significantly higher in comparison to the general population, with a standardized mortality ratio of 2.48 (95% CI:1.76-3.39) and no evidence of improvement over time.
Conclusions: SSc 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. SSc portends a 2.5-fold higher risk of mortality than the general population, with no evidence of improved survival over time.
Keywords: Systemic sclerosis; epidemiology; mortality; scleroderma; survival trends.