Background Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder with various ranges of organ damages, so that patients with SLE might face to considerable medical costs in their early disease courses. We aimed to estimate the progression of direct healthcare costs before and after diagnosis of SLE and to compare healthcare costs by disease severity in Korean patients with SLE.

Methods Incident patients with SLE were identified between 2008 and 2018 using the Korean National Health Insurance databases. Annual direct healthcare costs for five years before and after the diagnosis of SLE were estimated and we compared them with those of age-, sex-, and calendar months-matched controls (1:4). Direct healthcare costs of patients with SLE were compared by disease severity using inverse probability-weighted regression analysis.

Results A total of 11,173 incident SLE patients and 45,500 subjects without SLE were identified. Annual direct healthcare costs per person in SLE group was increasing one year before SLE diagnosis, and reached the highest at the first year of SLE diagnosis, resulting 7.7-fold greater than comparators ($5,694 vs. $736 a year, respectively). Among patients with SLE, having severe SLE resulted in 4.39 times (95% Confidence Interval [CI] 4.123–4.673) higher cost over a period of 1 year. Older age (aged 70–79, 1.455 times, 95% CI 1.304–1.623), having comorbidities such as lupus nephritis (1.89 times, 95% CI 1.801–1.983), avascular necrosis (5.482 times, 95% CI 3.977–7.668), chronic kidney diseases (1.783 times, 95% CI 1.601–1.985), and interstitial lung diseases (1.542 times, 95% CI 1.346–1.765) were associated with higher annual direct healthcare costs of the first year.

Conclusions Patients with SLE incurred significantly high direct healthcare costs compared to subjects without SLE, especially during the first year after diagnosis. Disease severity as well as comorbidities were associated with increased costs of illness in patients with SLE.