Key clinical point: In patients with hepatitis C virus infection, the incidence of Parkinson’s disease is lower among people who receive antiviral treatment.
Major finding: At 5 years, antiviral therapy was associated with a 25% reduced risk of Parkinson’s disease.
Study details: A population-based cohort study of 188,152 patients with hepatitis C virus infection.
Disclosures: The authors reported no conflicts of interest. The study was funded by grants from Chang Gung Medical Research Fund and from Chang Gung Memorial Hospital.
Lin W-Y et al. JAMA Neurol. 2019 Jun 5. doi: 10.1001/jamaneurol.2019.1368.
The findings of Lin et al. suggest a potentially modifiable hepatologic risk factor for Parkinson’s disease, Adolfo Ramirez-Zamora, MD, associate professor of neurology; Christopher W. Hess, MD, assistant professor of neurology; and David R. Nelson, MD, senior vice president for health affairs, all at the University of Florida in Gainesville, wrote in an accompanying editorial. Hepatitis C virus infection might enter the brain through the microvasculature and might induce microglial and macrophage-related inflammatory changes (JAMA Neurol. 2019 June 5. doi: 10.1001/jamaneurol.2019.1377).
Lin et al. estimated high diagnostic accuracy for Parkinson’s disease in their study. Nevertheless, clinical, neuroimaging, and pathological confirmation was unavailable, which is a limitation of their investigation, said Dr. Ramirez-Zamora and colleagues. “The diagnosis of Parkinson’s disease in early stages can be challenging, as other related conditions can mimic Parkinson’s disease, including cirrhosis-related parkinsonism. Moreover, using record-linkage systems excludes patients who did not seek medical advice or those who were misdiagnosed by symptoms alone, which may also underestimate the prevalence of Parkinson’s disease. Using population-based studies would be a more accurate method.”
Because interferon, which was the antiviral therapy used in this study, greatly affects the immune system and has a modest rate of eradicating viral hepatitis C infection, future research should examine the association between Parkinson’s disease and patients who cleared the virus, as well as patients who did not, said Dr. Ramirez-Zamora and colleagues. Such research could shed light on potential mechanisms of treatment response. Lin et al. did not examine the newer direct-acting antiviral therapies for hepatitis C virus infection, which cure more than 90% of patients. Nor did they analyze other well established lifestyle and demographic risk factors for developing the disease. In addition, “the authors could not generalize the results to those aged 75 years or older because of the substantially smaller number of patients in this age group,” said Dr. Ramirez-Zamora and colleagues.
Still, “identification of potentially treatable Parkinson’s disease risk factors presents a unique opportunity for treatment. Additional studies with detailed viral analysis and exposure are needed, including in other geographic and ethnic distributions,” they concluded.