A comprehensive analysis of approximately 500,000 medical records has uncovered compelling evidence linking severe viral infections, such as encephalitis and pneumonia, to an increased risk of neurodegenerative diseases, including Parkinson’s and Alzheimer’s. The study, conducted by researchers, identified 22 connections between viral infections and neurodegenerative conditions among the 450,000 individuals studied.

Notably, individuals treated for viral encephalitis, a type of brain inflammation, were found to be 31 times more likely to develop Alzheimer’s disease. For every 406 cases of viral encephalitis, approximately 6 percent (24 cases) went on to develop Alzheimer’s disease.

Patients hospitalized with pneumonia following flu infections exhibited a higher susceptibility to Alzheimer’s disease, dementia, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS). Additionally, intestinal infections, meningitis (often caused by a virus), and the varicella-zoster virus, responsible for shingles, were implicated in the development of various neurodegenerative diseases.

The study revealed that the impact of viral infections on the brain could persist for up to 15 years in some cases, and no instances were found where exposure to viruses had a protective effect.

Remarkably, approximately 80 percent of the viruses associated with brain diseases were classified as ‘neurotrophic,’ indicating their ability to cross the blood-brain barrier. The researchers emphasized the potential preventive role of vaccines, pointing out that vaccines are available for some of these viruses, such as influenza, shingles, and pneumonia.

The study builds upon earlier research, with a 2022 study linking the Epstein-Barr virus to a 32-fold increased risk of multiple sclerosis in more than 10 million people. The senior author, Michael Nalls, a neurogeneticist at the National Institute on Aging in the US, highlighted the innovative approach of using medical records for a comprehensive analysis, allowing for the systematic identification of potential links between viral exposure and neurodegenerative diseases.

Although this retrospective observational study does not establish a causal link, it contributes to the growing body of research suggesting the involvement of viruses in the development of Parkinson’s and Alzheimer’s disease. Co-author Andrew Singleton, a neurogeneticist and Alzheimer’s researcher, emphasized the significance of these findings, suggesting that viral infections and related inflammation in the nervous system may be common and potentially avoidable risk factors for neurodegenerative disorders.

By Impact Lab