January 24, 2023 – A latest evaluation shows that individuals hospitalized for viral infections equivalent to the flu usually tend to develop diseases that damage the nervous system, equivalent to Alzheimer's or Parkinson's, later in life.
Researchers found 22 links between viruses and customary neurological diseases that always occur in older people. The viruses included influenza, encephalitis, herpes, hepatitis, pneumonia, meningitis and shingles. These viruses have been linked to at least one or more of those diseases: Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS), dementia and multiple sclerosis.
The authors of the study, published this month within the journal Neuron, warned that their results weren't sufficient to say that the illnesses were attributable to the viruses.
“Neurodegenerative diseases are a collection of diseases for which there are very few effective treatments and many risk factors,” said study creator and National Institutes of Health researcher Andrew B. Singleton, PhD, in a Press release from the National Institutes of Health. “Our findings support the notion that viral infections and associated inflammation of the nervous system may be common – and potentially preventable – risk factors for these types of diseases.”
For the study, two data sets with a complete of 800,000 medical records from people in Finland and the UK were analyzed. People who were hospitalized with COVID-19 were excluded from the study.
Generalized dementia was the condition mostly related to viruses. People exposed to viral encephalitis, which causes brain inflammation, were 20 times more prone to develop Alzheimer's than people undiagnosed with this virus.
Both influenza and pneumonia were related to all neurodegenerative disease diagnoses studied, except multiple sclerosis. The researchers found that severe cases of influenza were related to probably the most risks.
“Remember, the people we studied did not have the common cold. Their infections made them sick enough to require hospitalization,” said study creator and NIH researcher Dr. Michael Nalls. “Nevertheless, the fact that commonly used vaccines reduce the risk or severity of many of the viral illnesses observed in this study raises the possibility that the risks of neurodegenerative diseases could also be reduced.”
The researchers examined the time period from infection with a virus to the time when an individual was diagnosed with one in all the neurodegenerative diseases. They found that almost all people were at high risk inside a yr of infection. However, in six cases, significant associations weren't seen until 5 to fifteen years later.
The authors write that vaccines can be found against a few of the viruses studied, which could reduce the danger of diseases that damage the nervous system.