Objectives To illuminate the association between interferon-based therapy (IBT) and the risk of rheumatoid arthritis (RA) in patients infected with hepatitis C virus (HCV). Design, setting, participants and interventions This retrospective cohort study used Taiwan's Longitudinal Health Insurance Database 2005 that included 18 971 patients with HCV infection between 1 January 1997 and 31 December 2012. We identified 1966 patients with HCV infection who received IBT (treated cohort) and used 1:4 propensity score-matching to select 7864 counterpart controls who did not receive IBT (untreated cohort). Outcome measures All study participants were followed until the end of 2012 to calculate the incidence rate and risk of incident RA. Results During the study period, 305 RA events (3.1%) occurred. The incidence rate of RA was significantly lower in the treated cohort than the untreated cohort (4.0 compared with 5.5 per 1000 person-years, p<0.018), and the adjusted HR remained significant at 0.63 (95% CI 0.43 to 0.94, p=0.023) in a Cox proportional hazards regression model. Multivariate stratified analyses revealed that the attenuation in RA risk was greater in men (0.35; 0.15 to 0.81, p=0.014) and men<60 years (0.29; 0.09 to 0.93, p=0.036). Conclusions This study demonstrates that IBT may reduce the risk of RA and contributes to growing evidence that HCV infection may lead to development of RA.
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