Increased Mortality in Asians With Systemic Sclerosis in Northern California

ObjectiveThe objective of this study is to evaluate racial/ethnic differences in disease manifestations and survival in a US cohort of patients with systemic sclerosis (SSc), with a focus on Asian patients. MethodsA retrospective cohort study was conducted among Kaiser Permanente Northern California adults with an incident SSc diagnosis by a rheumatologist from 2007 to 2016, confirmed by a chart review to fulfill 2013 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria. Self-reported race/ethnicity was categorized as non-Hispanic white, Asian, Hispanic, and black. Disease manifestations and survival were compared, using white patients as the reference. ResultsA total of 609 patients with incident SSc were identified: 89% were women, and 81% had limited cutaneous SSc, with a mean age at diagnosis of 55.4 14.8 years. The racial/ethnic distribution was 51% non-Hispanic white (n = 310), 25% Hispanic (n = 154), 16% Asian (n = 96), and 8% black (n = 49). Compared with white patients, black patients had a greater prevalence of diffuse disease (14.5% vs. 44.9%; P < 0.001), and Asians had higher rates of anti-U1-RNP antibodies (32.1% vs. 11.9%; P = 0.005). Nine-year overall survival rates following SSc diagnosis were lower in Asian (52.3%), black (52.2%), and Hispanic patients (68.2%) compared with white patients (75.8%). Pulmonary hypertension and infections were the leading causes of death in Asian patients. Asian race was associated with higher mortality on univariable (hazard ratio [HR] 1.83 [95% confidence interval (CI) 1.08-2.99]; P = 0.020) and multivariable analyses (HR 1.80 [95% CI 0.99-3.16]; P = 0.047) when adjusting for age, sex, body mass index, cutaneous subtype, smoking status, interstitial lung disease, pulmonary hypertension, renal crisis, and malabsorption syndrome. ConclusionAsian patients with SSc in this US cohort had increased mortality compared with white patients. These patients warrant close monitoring for disease progression.