Causal association of rheumatoid arthritis with frailty and the mediation role of inflammatory cytokines: a Mendelian randomization study

•Genetically predicted rheumatoid arthritis was associated with increased frailty index and Fried frailty score.•Neither genetically predicted frailty index nor Fried frailty score showed any association with the risk of rheumatoid arthritis.•Inflammatory cytokines were involved in the mechanism of rheumatoid arthritis-induced frailty.