Long-Term Epidemiology of Systemic Sclerosis in Western Australia: A Population-Level Linked Data Study.

Abstract

To report the prevalence, incidence and mortality of systemic sclerosis (SSc) in Western Australia (WA). This was a retrospective observational study, using whole-population linked administrative health data from the WA Rheumatic Disease Epidemiological Registry. All patients with an incident (first-ever) hospitalization with SSc between 1985 and 2013 were identified from discharge diagnosis fields and followed until end of 2014. Outcome measures were incidence rate (IR), point prevalence, standardized mortality ratio (SMR), and survival estimates using Cox regression, stratified by sex. In total 877 patients (mean age 58.6 years, 77.8% female, 3.2% Aboriginal and/or Torres Straits Islander people) had an incident hospitalization for SSc. The age-standardized IR of SSc ranged from 0.44 to 3.26 per 100,000 person-years and point prevalence averaged 37.93 per 100,000 population; both were higher for female individuals. During the study period, 452 (51.5%) patients died with crude mortality higher in male than female patients (66.2% vs 47.4%; <i>P</i> < 0.001). The SMR was 4.17 (95% CI 3.81-4.58), whereas 5- and 10-year survival rates were 67% and 52.4%, respectively. Age (hazard ratio [HR] 1.05, 95% CI 1.04-1.05), male sex (HR 1.56, 95% CI 1.27-1.92), heart failure (HR 1.88, 95% CI 1.36-2.60), kidney disease (HR 1.71, 95% CI 1.13-2.58), and cancer (HR 1.88, 95% CI 1.30-2.74) were independently associated with death. The main causes of death were SSc (n = 128, 28.3%), solid organ malignancy (n = 65, 14.4%), and ischemic heart disease (n = 47; 10.4%). The burden of SSc in WA exceeds global estimates and its high prevalence, high SMR, and number of deaths due to SSc as a primary cause suggest a large unmet therapeutic need.