Incidence and prevalence of systemic sclerosis in Valcamonica, Italy, during an 18-year period

Objectives: To investigate the epidemiology of systemic sclerosis in Valcamonica, an Italian Alpine valley, during an 18-year-long period. Methods: Patients with systemic sclerosis living in Valcamonica between 1999 and 2016 were identified by capture/recapture method using: (1) clinical databases of the only secondary Rheumatology Unit present in the valley and of the tertiary referral center for this area; (2) administrative data, extracting records with the International Classification of Diseases, 10th Revision, code for systemic sclerosis. Patients were included in the analysis when either the 1980 American Rheumatism Association classification criteria for systemic sclerosis or the 2013 American College of Rheumatology/European League Against Rheumatism criteria were satisfied. To study temporal changes, mean yearly incidence during three different 6-year interval was calculated. Prevalence rates were estimated at four different time points. Results: General population with age over 14 years living in Valcamonica varied during the evaluated period between 85,168 and 91,245 inhabitants. A total of 65 patients with systemic sclerosis were identified (female 84.6%, limited cutaneous systemic sclerosis: 84.6%; anticentromere: 64.6%). Systemic sclerosis incidence and prevalence increased during the study period (p = 0.029 and p < 0.0001, respectively). The increase of incidence was accounted for by cases satisfying only the 2013 criteria, with limited cutaneous systemic sclerosis, and with anticentromere, whereas the incidence of systemic sclerosis cases classified according to the 1980 criteria did not significantly increase. The prevalence at 31 December 2016 was 58.6 (95% confidence interval, 44.8-76.6) per 100,000 persons aged >14 years. Survival at 10 years after systemic sclerosis diagnosis was 83.0% (standard error, 5.6). Conclusion: Systemic sclerosis incidence and prevalence increased over time in this area, due to the increased recruitment of patients with milder forms of the disease.