Antiviral Therapy in Patients With Chronic Hepatitis C Is Associated With a Reduced Risk of Parkinsonism

BACKGROUND: The risk of parkinsonism after antiviral treatment against chronic hepatitis C (CHC) is unclear. OBJECTIVES: To investigate the association between CHC and parkinsonism and the efficacy of antiviral therapy. METHODS: Using the National Health Insurance Research Database of Taiwan from 2004 to 2012, patients with and without CHC, patients receiving pegylated interferon-based antiviral therapy, and those without such therapy were matched by age, gender, and comorbidities by propensity scores and followed for new diagnoses of parkinsonism and Parkinson's disease (PD). Multivariable Cox proportional hazards regression analyses were performed. RESULTS: Overall, 49,342 patients with CHC were matched with 49,342 non-CHC patients. After adjustment for confounding factors, there was a significantly increased risk (31%) of parkinsonism (hazard ratio [HR] 1.306; 95% confidence interval [CI], 1.208-1.412) in those with CHC and the risk of parkinsonism requiring anti-Parkinson medication (HR 1.323; 95% CI, 1.214-1.441). Furthermore, 23,647 untreated CHC patients were matched with 23,647 patients receiving antiviral therapy. Patients receiving antiviral therapy had a significantly lower risk of developing parkinsonism (38%; HR 0.618; 95% CI, 0.498-0.765) and a reduced risk of parkinsonism requiring anti-Parkinson medication (HR 0.651; 95% CI, 0.515-0.823). In sensitivity analyses, antiviral therapy significantly reduced the risk of parkinsonism and PD after adjustment for detection, selection, disease latency biases, and competing mortality. Our results suggest successful antiviral therapy associates with a reduced risk of hepatitis C virus-related parkinsonism compared with those with treatment failure. CONCLUSIONS: CHC infection is associated with an increased risk of parkinsonism or PD. Antiviral therapy against CHC is associated with a reduced risk of parkinsonism or PD.