Large Study Finds Link Between Viral Infections and Future Brain Illness

Scientists from the U.S. National Institutes of Health found a link between dozens of different viral exposures and a later increased risk of Alzheimer's disease and other brain disorders. Gizmodo reports: They analyzed data from two existing and nationally representative biobank projects tracking the long-term health of residents in Finland and the UK, respectively, collectively involving around 450,000 people. They looked for links between viral infections that led to hospitalization and six neurodegenerative diseases: Alzheimer's disease (the most common form of dementia), ALS, multiple sclerosis, Parkinson's disease, vascular dementia, and generalized dementia. In the Finland data, they initially identified 45 types of viral exposure potentially linked to a greater risk of neurodegenerative illness. To double-check these results, they then ran the same sort of analysis on the UK data and found a similar relationship for 22 types of viral exposure across both datasets. Some of these exposures involved specific viral infections, such as influenza, varicella zoster virus (the cause of chickenpox and shingles), and herpes simplex viruses. Others concerned where an infection or its harmful effects took place, such as viral encephalitis or meningitis, types of brain inflammation that can be caused by many different viruses. For some exposures, the risk of subsequent brain illness extended up to 15 years later, while the strongest link was seen between viral encephalitis and Alzheimer's. The team's findings were published earlier this month in Neuron. "As vaccines are currently available for some of the associated viruses, vaccination may be a way to reduce some risk of neurodegenerative disease," the authors note.

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