Objectives: Socioeconomic status (SES) has been found to be associated with worse outcomes of systemic lupus erythematosus (SLE). The impact of national health insurance on SLE outcomes has not been explored.
Methods: A retrospective inception cohort of patients older than 18 years with SLE diagnosed and followed in lupus clinics of two large tertiary medical centers were included. Patients were stratified into three groups by SES: lower 25th quantile, middle 25th-75th quantile, and upper 75th quantile. Primary outcomes were all-cause mortality, development of end-stage kidney disease (ESKD), and score ≤ 4 on the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI 2K) at the last visit.
Results: We identified 617 patients (548 females, 88.8%) with a median follow-up of 15 years (range, 8.0-23.0). Compared to the middle and upper SES groups, the lower SES group was characterized by younger age at disease onset (31.5 years vs. 34.3 and 37.4 years, respectively, p = 0.011) and higher rate of lupus nephritis (42.7% vs. 35.7% and 23.8%, respectively, p = 0.002). In multivariate models, patients in the middle and upper SES groups had a significantly lower risk of mortality (HR = 0.45; 95% CI, 0.24-0.82, p = 0.010) and ESKD (HR = 0.24; 95% CI, 0.08-0.73, p = 0.012), with no effect on the rate of SLEDAI 2K ≤ 4 (OR = 1.49; 95% CI, 0.92-2.40, p = 0.09).
Conclusion: Even within a health system that provides high and equal accessibility to medical care, low SES is associated with worse outcomes of SLE. Policymakers should focus on managing possible barriers that prevent patients of lower SES from obtaining optimal care.
Keywords: Systemic lupus erythematosus; damage; disease activity; lupus nephritis; mortality; socioeconomic status.