OBJECTIVES: Janus Kinase Inhibitors (JAKIs) are a recent advancement in Rheumatoid Arthritis (RA) treatment, offering an effective oral therapy option. However, adherence to JAKIs in RA patients is suboptimal compared to injectable options. Additionally, there is limited research on adherence to JAKIs among older adults in the United States. This descriptive study examined adherence to JAKIs among older RA patients enrolled in Medicare and identified predictors of poor adherence in this population.

METHODS: An observational cohort study was conducted using the 5% national Medicare administrative claims data from 2012 to 2020. A new-user design was employed to identify initiators of JAKIs between November 2012 and July 2020. Beneficiaries included in this study were required to have at least two prescriptions for JAKIs during the 6-month period post-initiation (follow-up period), at least one medical claim with the diagnosis of RA in the 6-month baseline period, and continuous part A, B, and D, but not part C enrollment during the 6-month baseline period and 6-month follow-up period. 6-month adherence in the follow-up period was estimated using the Proportion of Days Covered (PDC) measure. Finally, univariable logistic regression was performed to identify predictors of poor adherence.

RESULTS: Among 519 eligible beneficiaries, the majority of them were female (84.01%), White (75.53%), and mean (SD) age of 72.71 (5.95) years. The mean (SD) PDC was 0.75 (0.25), with 216 (41.62%) beneficiaries having poor adherence (PDC < 0.8) to JAKIs. Unadjusted analysis showed that while beneficiaries with higher Charlson Comorbidity Index (CCI) scores had greater odds of poor adherence to JAKIs (OR=1.46; 95%CI=1.01-2.12), beneficiaries with prior biologic disease-modifying antirheumatic drug use had lower odds of poor adherence to JAKIs (OR=0.69; 95%CI=0.48-0.99).

CONCLUSIONS: This study highlights the suboptimal adherence to JAKIs among older adults initiating therapy. Future research needs to examine long-term adherence to JAKIs and its determinants in this population.