The objective of the study was to compare the efficacy and safety of biological disease-modifying antirheumatic drugs (bDMARDs) between elderly-onset rheumatoid arthritis (EORA) and young-onset rheumatoid arthritis (YORA) patients. Patients with rheumatoid arthritis (RA) aged ≧18 years enrolled in a Japanese multicenter observational registry between 2009 and 2018 who had moderate or high disease activity when initiating bDMARDs were included. EORA was defined as RA with onset at 60 or over. After propensity score weighting for differences in confounding factors, generalized estimating equations were used to assess the relationship between the age of RA onset and bDMARD clinical effectiveness at 48 weeks after starting a bDMARD. Among a total of 7183 patients in the registry, 2815 (39.2%) were identified as EORA. The proportion of patients on bDMARDs was lower in the EORA as compared to the YORA (18.3% vs 28.0%, p
