Big Study Uncovers 22 Links Between Viral Infections And Brain Disease

New research looking at health records from nearly half a million people has identified 22 different associations between viral infections and neurodegenerative diseases.

Influenza, encephalitis and other viral infections all were linked to increased rates of brain diseases such as Parkinson’s, Alzheimer’s and MS. The idea that viral infections can play a role in the development of neurodegenerative disease isn’t particularly new.

Back in the 1950s microbial infections were suggested to be the source of many neurodegenerative diseases, with herpes in particular hypothesized to be deeply associated with the development of Alzheimer’s.

For each new neurodegenerative disease diagnosis the researchers looked at whether the patient had any record of a preceding viral infection.

After initially detecting 45 potential associations between viral infections and brain disease, the researchers tested those links in another database of 100,000 health records.

“The largest effect association was between viral encephalitis exposure and Alzheimer’s disease,” the researchers write in the study.

The findings certainly add to our growing understanding of the relationship between viral infections and neurodegenerative disease but they also raise some important questions that need to be answered.

The records could only track associations between infection and brain disease up to 15 years, for example, so there is no insight into potential long-term links.

Perhaps most significantly, the study found most links between brain disease and viral infections were strongest in the immediate year following an infection.

The more time that passed after a viral infection, the weaker the links that were detected.

Or, as the researchers speculate, it could be possible the early pre-symptomatic stages of neurodegenerative disease cause a type of immune dysregulation that makes a person more predisposed to suffering from severe viral infections.

If neurodegenerative disease is primarily accelerated by severe viral infections then vaccinations known to reduce the severity of illness could slow things down for many people.

“Their infections made them so sick that they had to go to the hospital. 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 disorders might also be mitigated.”