Abstract

Objectives

Rheumatoid arthritis (RA) is a chronic inflammatory disease commonly treated with high-cost biologic disease-modifying antirheumatic drugs (bDMARDs). As of May 2025, 12 bDMARDs (9 originators and 3 biosimilars) are approved in Japan, with 10 available for self-injection (SI). Although SI may reduce hospital visits, its overall impact on prescribing patterns and healthcare costs remains unclear.

Methods

We conducted a retrospective cohort study using Japanese health insurance claims data (DeSC Healthcare, April 2014-August 2023). Patients with RA were identified based on diagnostic codes and bDMARDs prescriptions. Patients initiating SI within 3 months of their first bDMARD prescription were classified as the SI group; others were assigned to the non-SI group. Propensity score matching (1:1) was performed using 25 covariates. From the public payer’s perspective, we compared monthly direct healthcare costs, bDMARDs prescription volume, and annual hospital visit frequency.

Results

A total of 6784 patients were matched (mean age: 73.5 years; 73.2% female). The SI group incurred higher monthly healthcare costs ($774.0; 95% confidence interval [CI]: 763.3-784.6) compared with the non-SI group ($608.3; 95% CI 598.3-618.4; P .05).

Conclusions

SI increased direct costs because of higher bDMARDs utilization but reduced hospital visits, suggesting a potential for indirect cost savings. These findings may support future reimbursement and care models for RA.