Study Finds Link between Hepatitis C and Parkinson's Disease

A Taiwanese study in Neurology suggests that patients who have the hepatitis C virus (HCV) are at a significantly higher risk of developing Parkinson’s disease (PD). The finding is not the first time a link between HCV and brain troubles has surfaced, but it is among the first to demonstrate a strong association between HCV and PD.

The finding is potentially important because of the wide worldwide prevalence of HCV and the fact that PD is a clinically devastating condition for which the etiology is not yet completely understood. Taiwan has high rates of HCV infection.

The current research was a population-based cohort study based on data obtained from a Taiwanese national registry from 2000 to 2010. A total of 49,967 patients with HCV were included for analysis. An additional control population of nearly 200,000 people without HCV were included for comparison. The mean age of the patients was about 46 years, and 43.5% of patients were women. Patients were followed for 12 years.

Patients with viral hepatitis were further grouped into 3 cohorts: hepatitis B virus (HBV) infection, HCV infection, and HBV-HCV coinfection. The researchers calculated the incidence of developing PD in each cohort, using a Cox proportional hazards model to estimate the risk of developing PD.

They found a strong association between HCV infection and developing PD. The crude hazard ration for developing PD was 0.66 (95% CI = 0.55—0.80) for HBV infection, 2.50 (95% CI = 2.07–3.02) for HCV infection, and 1.28 (95% CI = 0.88–1.85) for HBV-HCV coinfection. T

he association between HCV and PD remained statistically significant after adjustments for age, sex, and comorbidities (adjusted HR = 1.29, 95% CI = 1.06—1.56). The results amount to a 2.5-fold increased risk for PD in patients with HCV infection compared with controls (no HCV or HBV) (hazard ratio [HR], 2.5; 95% confidence interval [CI], 2.07 - 3.02).

The adjusted HRs for HBV and coinfection were not statistically significant. But the researchers noted that there were too few patients with PD in the coinfection category to attain statistical significance. Further research will be needed to establish the connection, if any, and shed further light on why HCV can lead to PD.

The theory, according to the study, is that neuro-inflammation triggered because of HCV ultimately leads to PD through a series of cytokines currently under additional study.

Also still to be studied is whether treatment for HCV, which has been revolutionized in recent years, ameliorates the increased risk for PD.