Long-term epidemiology of Systemic Sclerosis in Western Australia: a population-level linked data study.

Abstract

OBJECTIVE To report prevalence, incidence and mortality of Systemic Sclerosis (SSc) in Western Australia (WA). METHODS Retrospective observational study, using whole-population linked administrative health data from the Western Australia Rheumatic Disease Epidemiological Registry (WARDER). All patients with an incident (first-ever) hospitalisation with SSc between 1985-2013 identified from discharge diagnosis fields and followed until end of 2014. Outcome measures were incidence rates (IR), point prevalence, standardised mortality ratio (SMR) and survival estimates using Cox regression, stratified by gender. RESULTS In total 877 patients (mean age 58.6 years, 77.5% female, 3.2% Indigenous) had an incident hospitalisation for SSc. The aged-standardised 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 females. During the study period 452 (51.5%) patients died with crude mortality higher in males than females (66.2% vs 47.4%; p<0.001). The SMR was 4.17 (3.81-4.58) while five and ten-year survival rates were 67.0 % and 52.4% respectively. Age (HR=1.05; 95% CI:1.04-1.05), male sex (HR=1.56; 95% CI 1.26-1.92), heart failure (HR=1.88; 95% CI: 1.35-2.60), 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 ischaemic heart disease (n=47; 10.4%). CONCLUSION The burden of SSc in WA exceeds global estimates where its high prevalence, high SMR and number of deaths due to SSc as a primary cause suggest a large unmet therapeutic need.