Glucocorticoid sparing in rheumatoid arthritis patients treated with Janus kinase inhibitors: insights from the Japanese patient registry

Abstract Glucocorticoid (GC) use in rheumatoid arthritis (RA) remains concerning due to adverse effects. Janus kinase inhibitors (JAKi) may enable GC reduction or discontinuation. This study examined factors associated with GC use and the role of JAKi in achieving GC-free status using the 2022 National Database of Rheumatic Diseases in Japan (NinJa). Data from 8,555 RA patients were analyzed. Patient characteristics, disease activity, functional status, and treatments were compared between GC users and non-users. Multivariate logistic regression and propensity score–matched analyses assessed associations between GC use and disease-modifying anti-rheumatic drugs (DMARDs). Predictors of GC use in JAKi-treated patients were also evaluated, including causal mediation analysis. GC was used in 25% of patients (mean 3.77 mg/day). Users were more often male, with higher disease activity and disability. Methotrexate, TNF inhibitors, IL-6 inhibitors, and JAKi were linked to lower GC use. JAKi-treated patients had significantly less GC use and lower doses than biological (b)DMARD-free or bDMARD-treated groups. In JAKi users, higher Clinical Disease Activity Index (CDAI) predicted GC use and correlated with GC dose. Disease activity strongly influences GC use in RA. JAKi treatment is associated with lower GC use and may facilitate tapering in real-world practice.