Herpesvirus Infections and Risk of Parkinson's Disease

Introduction: Herpesviruses might play a role in the pathogenesis of neurodegenerative disorders. We sought to examine a possible association between alpha herpesvirus infections and Parkinson’s disease. Methods: We conducted a population-based case-control study of incident Parkinson’s disease in 2009 Medicare beneficiaries age 66–90 years (89,790 cases, 118,095 randomly selected comparable controls). We classified beneficiaries with any diagnosis code for “herpes simplex” and/or “herpes zoster” in the previous 5 years as having had the respective alpha herpesviruses. In beneficiaries with Part D prescription coverage, we also identified those prescribed anti-herpetic medications. We calculated odds ratios (OR) and 95% CI between alpha herpesvirus diagnosis/treatment and Parkinson’s disease with logistic regression, with adjustment for age, sex, race/ethnicity, smoking, and use of medical care. Results: Parkinson’s disease risk was inversely associated with herpes simplex (OR 0.79, 95% CI 0.74–0.84), herpes zoster (OR 0.88, 95% CI 0.85–0.91), and anti-herpetic medications (OR 0.87, 95% CI 0.80–0.96). Conclusion: Herpesvirus infection or treatment might reduce risk of Parkinson’s disease, but future studies will be required to explore whether this inverse association is causal.