Introduction: Biologics effectively manage symptoms and disease activity in rheumatoid arthritis (RA), but their long-term effects remain unclear.

Method: Longitudinal data were examined from the Brigham and Women's Rheumatoid Arthritis Sequential Study (BRASS) registry. Linear regression modeled the effect of biologic exposure on changes in disease activity (Disease Activity Score-28 with C-reactive protein [DAS28-CRP]), functional status (modified Health Assessment Questionnaire [mHAQ]), and RA severity (Routine Assessment of Patient Index Data [RAPID3]). Biologic exposure was the ratio of time on a biologic relative to time participating in the BRASS cohort.

Results: The analysis included 1395 RA patients, 82.3% female, with 6783 unique study visits from 2003 to 2015. At the patient's first visit, mean (SD) age was 56.3 (14.2) years and mean (SD) duration of RA was 12.7 (11.9) years. Average follow-up duration was 5.59 years (range, 1-13). Over time, DAS28-CRP, mHAQ, and RAPID3 scores decreased as the biologic exposure ratio increased. In repeated measures regression models, increased biologic exposure was significantly associated with decreased DAS28-CRP score (β = - 0.647; P < 0.001), decreased mHAQ score (β = - 0.096; P < 0.001), and decreased RAPID3 score (β = - 0.724; P < 0.001) during follow-up. Methotrexate use at baseline predicted decreased DAS28-CRP, mHAQ, and RAPID3 scores during follow-up. Biologic use at baseline predicted increased DAS28-CRP or mHAQ during follow-up.

Conclusions: Increased biologic exposure is associated with decreased disease activity, function impairment, and RA severity. Future studies should examine whether earlier initiation of biologics improves patient outcomes in RA.

Trial registration: ClinicalTrials.gov , NCT01793103 Key Points • Biologics effectively manage symptoms and disease activity in rheumatoid arthritis (RA), but their long-term effects remain unclear. • In this analysis of longitudinal annual population samples of 1395 RA patients in the Brigham and Women's Rheumatoid Arthritis Sequential Study (BRASS) registry, disease activity, function, and severity scores improved as time on biologic therapy increased. • In repeated measures regression models, time on biologic therapy was a significant predictor of improved outcomes for disease activity, function, and RA severity. • Further studies should examine whether earlier initiation of biologics limits the long-term effect of inflammation on RA outcomes.