Neurodegenerative diseases are diseases in which nerve cells in the brain and spinal cord gradually die over a long period of time. These include Alzheimer’s, ALS, Parkinson’s and multiple sclerosis. Using the information in a Finnish biodatabase FinnGen and a British database, researchers identified 22 virus-disease pairs in which infection with the virus was associated with an increased risk of such diseases. Viral encephalitis had the greatest impact on the risk of later developing Alzheimer’s. Influenza infection with pneumonia increased the risk of five of the six neurodegenerative diseases. However, gastrointestinal infections or contact with the varicella-zoster virus, which causes chickenpox and shingles, are also associated with an increased risk of diseases such as Alzheimer’s, MS or Parkinson’s. In some cases, the risk of disease remained elevated for 15 years after infection.
Vaccinations can protect
According to the scientists, since some viral diseases such as influenza, chickenpox and shingles can be prevented by vaccination, they could at least partially reduce the risk of such neurodegenerative diseases. The virologist Professor Dr. Klaus Überla from the University Hospital Erlangen points out: “Before vaccinations are now recommended to protect against neurodegenerative diseases, it would be important to show that vaccinations do indeed reduce the frequency of neurodegenerative diseases.” In addition, it must be checked how many people are vaccinated need to prevent a case of neurodegenerative disease. The study is therefore an important impetus for further research.
Further studies are necessary
In the study, the connections between infection and disease could be proven in two different databases. However, this does not prove that the viral infections are really to blame for the neurodegenerative diseases. “It could also be the case, for example, that people who tend to go through severe viral infections also have an increased risk of neurodegenerative diseases,” says Überla.
Nevertheless, the study is “very relevant”, judges Professor Dr. Martin Korte, head of the Neuroinflammation and Neurodegeneration working group at the Helmholtz Center for Infection Research in Braunschweig. In a mouse model, it was shown that influenza viruses in particular also activate cells of the immune system in the brain that are suspected of damaging nerve cells over a longer period of time.
Source: 10.1016/j.neuron.2022.12.029