Prevalence, incidence, survival, and disease characteristics of systemic sclerosis in a large US population

To estimate the prevalence, incidence, survival, and disease characteristics of systemic sclerosis (SSc) in the Detroit tricounty area.

A census of SSc cases for the period 1989-1991 was conducted in the Detroit area, using multiple sources for case identification. Diagnoses were verified by medical record review. Capture-recapture analysis was used to estimate the total SSc population. Cases of localized scleroderma (morphea and linear disease) were excluded.

Based on 706 verified cases of SSc, prevalence was initially estimated to be 242.0 cases per million adults (95% confidence interval [95% CI] 213-274), with an annual incidence of 19.3 new cases per million adults per year (95% CI 12.4-30.2). Capture-recapture analysis, based on the degree of overlap of verified cases among multiple sources, resulted in a revised prevalence estimate of 276 cases per million adults (95% CI 245-310). Sex- and race-specific prevalence estimates were significantly higher for women than for men, and for blacks than for whites. The average age at diagnosis was significantly younger for blacks than for whites. Compared with white patients, black patients were almost twice as likely to have diffuse disease (prevalence proportion ratio 1.86, 95% CI 1.48-2.35). Median survival was approximately 11 years. Factors negatively affecting survival included male sex (hazard ratio 1.81, 95% CI 1.29-2.55) and older age at diagnosis (hazard ratio 1.04, 95% CI 1.03-1.05).

This study establishes baseline estimates of SSc occurrence and characteristics in a large US cohort consisting primarily of black adults and white adults. These data should facilitate research regarding the role of geographic, ethnic, racial, and environmental factors for this disease in comparison populations.