A study of about 500,000 medical records suggested that severe viral infections such as encephalitis and pneumonia increase the risk of neurodegenerative diseases such as Parkinson’s disease and Alzheimer’s disease.
Researchers found 22 associations between viral infections and neurodegenerative conditions in a study of about 450,000 people.
People treated for a type of brain inflammation called viral encephalitis were 31 times more likely to develop Alzheimer’s disease. (For every 406 cases of viral encephalitis, 24 people developed Alzheimer’s disease, which is about 6%.)
People hospitalized with pneumonia after getting the flu seem to be more likely to develop Alzheimer’s disease, dementia, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS).
Intestinal infections and meningitis (both often caused by viruses), as well as the varicella-zoster virus that causes shingles, are also thought to be involved in the development of several neurodegenerative diseases. .
The effects of the viral infection on the brain lasted for up to 15 years in some cases. Additionally, there were no cases in which exposure to the virus provided protection.
About 80% of viruses associated with brain diseases are considered “neurotrophic,” meaning they can cross the blood-brain barrier.
“Surprisingly, vaccines are now available for some viruses such as influenza and shingles (varicella zoster), pneumonia,” the researchers said. I have written.
“While vaccines do not prevent all diseases, they are known to dramatically reduce hospitalization rates. This evidence suggests that vaccination may reduce the risk of developing neurodegenerative diseases to some extent. I am.”
Survey targeting over 10 million people in 2022 Links Epstein-Barr virus with 32-fold increased risk of multiple sclerosis.
“After reading [this] The study found that for years, scientists have been looking at links between individual neurodegenerative diseases and specific viruses one by one. ” Said Senior author Michael Nalls is a neurogeneticist at the National Institute on Aging.
“That’s when we decided to try a different, more data science-based approach,” he says. Said. “Using medical records, we were able to systematically search for all possible connections in one shot.”
First, the researchers analyzed the medical records of about 35,000 Finns with six types of neurodegenerative diseases and compared them with a control group of 310,000 people without brain diseases.
This analysis yielded 45 associations between viral exposure and neurodegenerative diseases, which were narrowed down to 22 in a subsequent analysis of 100,000 UK Biobank medical records.
Although this retrospective observational study cannot prove causality, mountain of research Suggests a role for viruses in Parkinson’s and Alzheimer’s disease.
“Neurodegenerative diseases are a group of diseases for which there are few effective treatments and many risk factors.” Said Co-author Andrew Singleton is a neurogeneticist, Alzheimer’s disease researcher, and director of the Center for Alzheimer’s Disease and Related Dementias.
“Our results support the idea that viral infections and associated inflammation in the nervous system may be a common and possibly avoidable risk factor for this type of disease. ”
This research neuron.
A previous version of this article was published in January 2023.
