Viruses have long been associated with neurodegenerative diseases. An example of this is the herpes virus and its potential role in Alzheimer’s dementia. A study published in 2022 also provided the most powerful study yet Evidence that Epstein-Barr virus may cause multiple sclerosis. However, many of these studies only looked at one specific virus and brain disease.
Kristen Levine and her colleagues at the National Institutes of Health in Bethesda analyzed nearly 450,000 electronic health records in the United States and found one A link has been found between various viruses and an increased risk of developing neurodegenerative diseases such as Alzheimer’s or Parkinson’s. However, experts point out that the data only shows an association and that it is still not clear whether or not the infection causes the outbreak. One of the strongest associations has been between encephalitis, an inflammation of the brain caused by several types of viruses, and Alzheimer’s disease. This infection increased the likelihood of developing dementia later in life by 31-fold. Most of the other associations were weaker: People who had the flu (influenza virus) and then pneumonia were four times more likely to develop Alzheimer’s disease in their lifetime than those who did not have such an infection according to medical records.
Kjetil Bjornevik, an epidemiologist at the Harvard TH Chan School of Public Health in Boston, notes that Levine’s approach to using medical records could be problematic. As a result, only infections that were severe enough to warrant a visit to the doctor were taken into account. Inclusion of milder cases may weaken connections. It is also unclear whether the viral infection led to a neurodegenerative disease or whether this made them more susceptible to infection. Another theory is that viruses speed up molecular changes in the body that were already underway, says Cornelia van Duijn of the University of Oxford.
