A new study that looked at the health records of nearly half a million people identified 22 different associations between viral infections and neurodegenerative diseases. Influenza, encephalitis and other viral infections have all been associated with increased incidence of brain diseases such as Parkinson’s disease, Alzheimer’s disease and multiple sclerosis.
The idea that viral infections may play a role in the development of neurodegenerative diseases is not particularly new. In the 1950s, microbial infections were suggested to be the cause of many neurodegenerative diseases, and herpes in particular was hypothesized to be closely related to the development of Alzheimer’s disease.
The idea has been on the fringes of neuroscience for decades, but it’s recently entering the mainstream after several important studies uncovered strong new evidence. A recent study presented strong causal evidence linking the development of multiple sclerosis (MS) with Epstein-Barr virus (EBV) infection.
“After reading the Epstein-Barr virus study, I realized that for years, scientists had been looking for links between individual neurodegenerative diseases and specific viruses, one by one,” Senior said. Author Michael Nulls explains the origins of this new study…”That’s when we decided to try a different, more data science-based approach. I was able to systematically search all possible links in one shot.”
The first part of the study examined 300,000 medical records, focusing on new diagnoses of either Alzheimer’s disease, ALS, systemic dementia, multiple sclerosis, Parkinson’s disease, or vascular dementia. . For each new neurodegenerative disease diagnosis, researchers looked to see if patients had a record of previous viral infections.
After initially detecting 45 potential associations between viral infections and brain disease, researchers tested those links in another database of 100,000 health records. focused on a particular association of
“The greatest effect association was between exposure to viral encephalitis and Alzheimer’s disease,” the researchers wrote in the study. Five of these were significantly associated with Epstein-Barr/multiple sclerosis, and several of these exposures were associated with increased risk of neurodegeneration up to 15 years post-infection. was doing.”
While this finding certainly helps us to better understand the relationship between viral infections and neurodegenerative diseases, it also raises some important questions that need answers. For example, our records only tracked the association between infections and brain disease for up to 15 years, so we have no insight into potential long-term associations.
Perhaps most importantly, the study found that most associations between brain disease and viral infection were strongest in the year immediately following infection. The longer the virus infection has passed, the weaker the detected links will be.
This means that viral infections may only accelerate degenerative processes that are already underway and may not trigger early onset. It is possible that the early, pre-onset stages of HIV cause a form of immune dysregulation that predisposes to severe viral infections.
“Many studies support the idea that the neurodegenerative process begins many years (10 to 20 years) before diagnosis,” the researchers wrote. “For example, a hospitalization for influenza with pneumonia recorded five years before NDD diagnosis may actually occur five years after the degenerative process has already begun. If you have the virus, you can expect to see more cases of the virus after diagnosis if your body is affected by NDD before diagnosis.
Nalls said the findings raise the possibility that broader deployment of generic vaccines could potentially reduce the incidence of neurodegenerative diseases. If neurodegenerative diseases are primarily accelerated by severe viral infections, vaccination, which is known to reduce the severity of the disease, may slow the condition for many people. It has been detected to some extent in studies linking influenza vaccination to a reduced risk of Alzheimer’s disease in older adults.
“Keep in mind that the people we surveyed did not have colds,” said Nulls. Nevertheless, the fact that commonly used vaccines reduce the risk or severity of many of the viral diseases observed in this study suggests that the risk of neurodegenerative diseases may also be reduced. raise it.”
A new study was published in a journal neuron.
Source: NIH
