WASHINGTON – In a case of welcome unintended consequences, the VA might be lowering the risk of Parkinson’s disease by treating another common condition: hepatitis C virus.

An unresolved question is whether the treatment, which is no longer in widespread use, or the elimination of HCV possibly provided protection against Parkinson’s.

A large study of patients infected with HCV published in JAMA Neurology found that treating the infection reduced the risk of developing Parkinson’s disease.1 If that’s borne out in subsequent studies, it could indicate an additional benefit to the VA’s successful program to eliminate hepatitis C in veterans.

The retrospective cohort study of 188,152 patients with HCV compared those treated with interferon therapy between January 1, 2003 and December 31, 2013 to a propensity score-matched group who did not receive treatment. The untreated group was 40% more likely to develop Parkinson’s disease.

“The advantage of antiviral therapy reached statistical significance at the five-year follow-up (HR, 0.75; 95% CI, 0.59-0.96), and this advantage continued to increase until the end of follow-up (HR, 0.71; 95% CI, 0.58-0.87),” the researchers reported.

While the results are encouraging, Jane Battles, PhD, scientific program manager in the VA’s Office of Research and Development urged caution in extrapolating the results to the VA because of demographic and treatment differences.

“The treatment used in this cohort was interferon-based, which is a general regimen used to stimulate immune and anti-inflammatory responses and not well-tolerated by most patients,” she told U.S. Medicine. “It is no longer the treatment of choice for hepatitis C infections in the U.S. veteran population.”

The VA has cured hepatitis C in more than 100,000 veterans, nearly all of them since the development of oral direct-acting antivirals in 2014. The newer generation of HCV medications are much better tolerated and far more effective than interferon, raising the cure rate from 36% to more than 90%.


  1. 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. JAMA Neurol. Published online June 05, 2019.