Patients infected with hepatitis C virus (HCV) are at increased risk of developing Parkinson disease, according to research published online ahead of print December 23, 2015, in Neurology.

Senior author Chia-Hung Kao, MD, and fellow investigators analyzed data from the Taiwan National Health Insurance Research Database between 2000 and 2010 on 199,868 people without a viral hepatitis infection and 49,967 patients infected with viral hepatitis (hepatitis B virus [HBV], 71%; HCV, 21%; both HBV and HCV, 8%). In Taiwan during the study period, blood transfusions were the most common cause of the hepatitis infection (in the United States, all donated blood has been screened for hepatitis since 1992).

Over an average follow-up of 12 years, the researchers found that people with HCV infection were almost 30% more likely to develop Parkinson disease, when compared with those who were not infected with hepatitis. People infected with HBV or both HBV and HCV were not more or less likely to develop Parkinson disease than those who did not have hepatitis.