A viral illness may increase risk of Alzheimer’s disease

Credit: Sinisa Maric/Pixabay.

In a study from the National Institutes of Health, scientists found a viral illness may increase a person’s chances of later developing Alzheimer’s disease.

They analyzed the medical records of hundreds of thousands of people in Finland and the United Kingdom.

The researchers found there may be at least 22 pairings between a neurodegenerative disease diagnosis and a previous viral infection that led to a hospital visit.

The strongest risk association was between viral encephalitis—an inflammation of the brain caused by a virus—and Alzheimer’s disease.

Meanwhile, hospitalizations due to pneumonia-causing flu viruses were linked to the diagnoses of several disorders, including dementia, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS).

The study results also raised the possibility that existing vaccinations may help some people reduce their chances of experiencing these disorders.

The results support the idea that viral infections and related inflammation in the nervous system may be common—and possibly avoidable—risk factors for these types of disorders.

Neurodegenerative disorders damage different parts of the nervous system. Typically, this happens later in life and produces a variety of problems, including thinking, remembering, and moving.

Several previous studies have suggested that certain viruses may play a role in each of these disorders.

In the study, the team found 45 significant associations between a neurodegenerative disease diagnosis and a previous viral infection.

That number narrowed to 22 associations after the scientists performed a second search of UKBiobank, which contains the records of 500,000 individuals from the United Kingdom.

Of all the neurodegenerative disorders, generalized dementia had the most associations, with links to six different virus exposures.

Individuals who had viral encephalitis were at least 20 times more likely to be diagnosed with Alzheimer’s than those who did not experience that virus.

Severe cases of influenza were linked to the widest range of risks. Influenza and pneumonia exposures were linked to all the neurodegenerative disorder diagnoses except multiple sclerosis.

The team says that about 80% of the viruses observed in this study can invade the nervous system and trigger the immune system’s inflammatory response.

In the future, they plan to use the latest data science tools to not only find more pieces but also help researchers understand how those pieces, including genes and other risk factors, fit together.

If you care about Alzheimer’s, please read studies about daytime napping strongly linked to Alzheimer’s disease, and how to treat mild to moderate Alzheimer’s disease.

For more information about brain health, please see recent studies about alternative drug strategy against Alzheimer’s disease, and these antioxidants could help reduce dementia risk.

The study was conducted by Andrew B. Singleton et al and published in Neuron.

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