Patients with hepatitis C virus (HCV) who are treated with interferon (IFN)-based antiviral medications have a significantly reduced risk of developing Parkinson disease compared with patients who do not receive this treatment, according to study results published in JAMA Neurology.

The investigators of this population-based cohort study sought to explore the association between IFN-based antiviral therapy and the development of Parkinson disease in patients with chronic HCV infection. The study included 188,152 adults with a new HCV diagnosis, with or without hepatitis, from the Taiwan National Health Insurance Research Database between January 2003 and December 2013.

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Researchers categorized participants according to whether they were treated with antiviral therapy or not. They used propensity scores to match participants from the treated (n=39,936) and untreated (n=39,936) groups by age and sex and by confounding covariates. The primary outcome was development of Parkinson disease. Investigators compared risk for Parkinson disease between groups using hazard ratios (HRs) calculated at years 1, 3, and 5 and at the end of the follow-up period.

The incidence density of Parkinson disease in the treated group was 1/1000 PY (95% CI, 0.85-1.15) and in the untreated group was 1.39/1000 PY (95% CI, 1.21-1.57). Although the incidence density increased gradually over time in both groups, the rate of increase in the treated group (3.03-4.06/1000 PY) was significantly slower vs the untreated group (3.93-5.51/1000 PY). The difference in risk between groups was not significant at year 1 and 3; however, it was considered statistically significant at year 5 (HR 0.75; 95% CI, 0.59-0.96) and through the end of follow-up (HR 0.71; 95% CI, 0.58-0.87).

Limitations to the study included the lack of data on hepatic function profiles, which prevent the association of Parkinson disease incidence with severity of HCV infection, and lack of patient lifestyle information, which may affect incidence of Parkinson disease. In addition, there were potential issues with diagnosing Parkinson disease, and the follow-up period was not long enough to observe the full course of infection and treatment, as Parkinson disease is a slow, progressive disorder.

The researchers concluded that patients with chronic HCV who received IFN-based antiviral medications demonstrated a reduced incidence of Parkinson disease compared with patients who did not receive this treatment. They suggested that HCV could be a risk factor for Parkinson disease and that IFN-based antiviral therapy may lower this risk.

Reference

Lin WY, Lin MS, Weng YH, et al. Association of antiviral therapy with risk of Parkinson disease in patients with chronic hepatitis C virus infection [published online June 5, 2019]. JAMA Neurol. doi:10.1001/jamaneurol.2019.1368