Association of Antiviral Therapy With Risk of Parkinson Disease in Patients With Chronic Hepatitis C Virus Infection

Key PointsQuestionIs interferon-based antiviral therapy associated with Parkinson disease incidence in patients with chronic hepatitis C virus infection? FindingsIn this cohort study of 188152 patients with hepatitis C virus infection, the group treated with antiviral therapy had lower incidence density and risk of developing PD compared with the untreated group. MeaningResults of treatment with interferon-based antiviral therapy appeared to support the hypothesis that hepatitis C virus may be a probable risk factor for Parkinson disease. ImportanceEpidemiologic evidence suggests that hepatitis C virus (HCV) could be a risk factor for Parkinson disease (PD), but treatment for HCV infection has never been considered in these studies; hence, the association between antiviral therapy and PD incidence has remained unclear. Understanding this association may help in developing strategies to reduce PD occurrence. ObjectiveTo identify the risk of PD development in patients with HCV infection receiving antiviral treatment and in patients not receiving this treatment. Design, Setting, and ParticipantsThis cohort study obtained claims data from the Taiwan National Health Insurance Research Database. Adult patients with a new HCV diagnosis with or without hepatitis per International Classification of Diseases, Ninth Revision, Clinical Modification codes and anti-PD medications from January 1, 2003, to December 31, 2013, were selected for inclusion. After excluding participants not eligible for analysis, the remaining patients (n=188152) were categorized into treated and untreated groups according to whether they received antiviral therapy. Propensity score matching was performed to balance the covariates across groups for comparison of main outcomes. This study was conducted from July 1, 2017, to December 31, 2017. Main Outcomes and MeasuresDevelopment of PD was the main outcome. A Cox proportional hazards regression model was used to compare the risk of PD, and the hazard ratio (HR) was calculated at 1 year, 3 years, and 5 years after the index date and at the end of the cohort. ResultsA total of 188152 patients were included in the analysis. An equal number (n=39936) and comparable characteristics of participants were retained in the treated group (with 17970 female [45.0%] and a mean [SD] age of 52.8 [11.4] years) and untreated group (with 17725 female [44.4%] and a mean [SD] age of 52.5 [12.9] years) after matching. The incidence density of PD was 1.00 (95% CI, 0.85-1.15) in the treated group and 1.39 (95% CI, 1.21-1.57) per 1000 person-years in the untreated group. The advantage of antiviral therapy reached statistical significance at the 5-year follow-up (HR, 0.75; 95% CI, 0.59-0.96), and this advantage continued to increase until the end of follow-up (HR, 0.71; 95% CI, 0.58-0.87). Conclusions and RelevanceEvidence suggested that the PD incidence was lower in patients with chronic HCV infection who received interferon-based antiviral therapy; this finding may support the hypothesis that HCV could be a risk factor for PD. This cohort study uses claims data and diagnostic coding in a large national database of Taiwanese patients to identify the association between the hepatitis C virus, treatment regimens for this infection, and Parkinson disease prescriptions.