Evidence Suggests HCV Could Be a Risk Factor for Parkinson Disease

Epidemiological evidence suggests that hepatitus C infection may be a risk factor for developing Parkinson disease.

Evidence suggests that infection with hepatitis C virus (HCV) may increase the risk of developing Parkinson disease (PD), according to new study in JAMA Neurology.

“Several epidemiologic studies found an association between HCV infection and PD, and HCV infection has been suggested as a risk factor for PD,” researchers said. “However, inconsistent results showing no association between HCV infection and PD have also been reported.”

Researchers investigated patients with chronic HCV infection who were either treated with antiviral therapy or untreated and compared the incidence of PD between the cohorts.

The study was conducted from July 1, 2017, to December 31, 2017. Researchers obtained claims data from the Taiwan National Health Insurance Research Database, which included information about all healthcare services covered by Taiwan National Health Insurance, a single-payer insurer that provided coverage to nearly 99% of Taiwan’s population.

Individuals recently diagnosed with HCV, with or without hepatitis, according to International Classification of Diseases, Ninth Revision, Clinical Modification codes, were selected for potential inclusion from January 1, 2003 to December 31, 2013. Patients who were identified on the index date as being 20 years old or younger, who had major hepatic diseases, or were diagnosed with PD, dementia, or stroke were excluded from the study. The index date was defined as the time HCV infection or carrier status was first confirmed in patients who were untreated. For those who were treated, the index date was defined as the time interferon-based antiviral therapy was initiated.

After exclusions, a total of 188,152 individuals were selected for data analysis. Participants were categorized into 1 of 2 groups depending on whether they received antiviral treatment. Researchers performed propensity score matching to balance covariates across groups for comparison of main outcomes.

The primary outcome in the study was development of PD. Researchers used a Cox proportional hazards regression to compare risks of PD development. They calculated hazard ratios 1 year, 3 years, and 5 years after the index date and at the end of the cohort.

After matching, an equal number of participants with comparable characteristics were retained in both groups. Researchers found the incidence density of PD was 1.00 per 1000 person-years in the group that received antiviral treatment and 1.39 in the untreated group. Between both groups, the risk of PD was no different at year 1 or year 3 but was found to be statistically significantly different at year 5 of follow-up. The event number and incidence density grew gradually over time in both groups. Researchers also found the event rate in the treated group increased statistically significantly slower than in the untreated group.

“This study found that PD incidence appeared to be lower in patients who were receiving interferon-based antiviral therapy for chronic HCV infection. The results seem to support the theory that HCV infection is a risk factor for developing PD. Antiviral therapy has shown potential in lowering this risk,” researchers concluded.


Lin W, Lin M, Weng Y, 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.