Neurogeneticist Michael Nalls of the US National Institute on Aging recently told Science Alert that a 2022 study, published in the Journal of Alzheimer’s Disease, completely changed their discovery approach.
Dr. Nalls said they realized that for years scientists were searching for links between a specific virus and an individual neurodegenerative disorder. Simply one-to-one. To the contrary, Tufts and Oxford University researchers reported that two common viruses may trigger Alzheimer’s disease. Namely herpes simplex (HSV) and dvaricella zoster (VZV) viruses. The premise is that VZV, which causes shingles and chickenpox, activates HSV.
When HSV-1 is activated, it creates an accumulation of amyloid beta proteins and tau accumulation generally found in Alzheimer’s patients. Dr. Nalls referred to a statement by Dana Cairns, a Tufts research associate who explained that VZV causes inflammation that in turn triggers HSV.
About the New Approach
The new approach, according to Dr. Nalls, is primarily data science-based using medical records. The doctor noted that using medical records allowed the team to search every possible link at once. The team began by searching approximately 35,000 people in Finland, who had six types of neurological diseases, against 310,000 controls who did not show evidence of brain disease. As a result, twenty-two connections were discovered between neurodegenerative conditions and viral infections after studying approximately 450,000 individuals.
People with viral encephalitis were 31 times more susceptible to Alzheimer’s. Note that 24 people or 6% of those tested eventually developed Alzheimer’s disease. Dr. Nalls and his team also found that people who were hospitalized after having the flu, which then developed into pneumonia, were especially susceptible to Alzheimer’s disease, Parkinson’s, and ALS. It is noteworthy that approximately eighty percent of viruses causing diseases of the brain are “neurotrophic” meaning that they are able to cross the blood-brain barrier.
The researchers also noted that at the present time vaccines do exist for shingles, influenza, and pneumonia. Although vaccines to not always prevent illness, they play a role of reducing some of the risk that accompanies neurodegenerative disease. The analysis brought about 45 links between neurodegenerative diseases and viral exposure. These numbers were reduced to 22 links in another analysis of approximately 100,000 medical records obtained from the United Kingdom’s Biobank.
The study adds to the new research that is being compiled in favor of viruses associated with Alzheimer’s and Parkinson’s disease. Andrew Singleton is a neurogeneticist, co-author and director at Alzheimer’s Center for related diseases. Dr. Singleton stated that the study, which has been published in Neuron, supports the theory that neurodegenerative disorders are actually a collection of diseases that may only have a few effective treatments but carry many risk factors.
