Not only against the flu
Flu shot reduces risk of Alzheimer's disease
Alzheimer's disease, which is a common cause of senile dementia, affects more than 6 million people in the United States alone, and this number is growing – along with an increase in life expectancy. There is no effective treatment for this disease yet, and many researchers are directing their efforts to develop ways to prevent it.
More and more evidence indicates that the risk of developing and progressing Alzheimer's disease is influenced by systemic reactions of the immune system. For example, the rate of cognitive decline is associated with the disease of elderly people with infections, including influenza. Then preventing microbial-induced inflammatory reactions may be a working strategy to reduce the risk of neurodegenerative pathology.
In accordance with this hypothesis, a number of studies have shown that the risk of senile dementia is lower in those people who received various vaccinations in adulthood. In particular, it was assumed that a link was found between influenza vaccination and the incidence of Alzheimer's disease. But the shortcomings of the planning of these studies did not allow us to draw unambiguous conclusions.
Now scientists from the University of Texas Health Science Center in Houston (USA) have studied the relationship between influenza vaccination and the risk of Alzheimer's disease in a large population of US residents aged 65 years and older. They analyzed data from almost two million people, half of whom were vaccinated against influenza over a 4-year follow–up period, and half did not. Alzheimer's disease developed during this time in 5.1% of vaccinated and 8.5% of unvaccinated patients, that is, vaccination reduced the likelihood of developing Alzheimer's disease by 40%. The strength of the protective effect increased with the number of years during which a person was vaccinated: protection was maximum for those who were vaccinated annually.
The mechanisms of this effect are not yet precisely known. Scientists offer several options. For example, it may be the similarity of epitopes ("pieces" of molecules that are recognized by the immune system) of influenza virus proteins and pathological proteins found in Alzheimer's disease. In addition, the defeat of the central nervous system in influenza can contribute to the development of manifestations of Alzheimer's disease, and, accordingly, the prevention of influenza can prevent associated pathological changes in the brain.
On the other hand, and scientists are inclined to this option, the protective effect may not be specific to the influenza vaccine, but common to different vaccines. Vaccination can permanently "reprogram" the work of immune cells, regulating the work of their genes using epigenetic (supra-genomic) mechanisms. As a result, the immune system becomes more "trained" – and able to better cope with solving its tasks.
The exact elucidation of the mechanisms underlying the effect of influenza vaccination on the risk of Alzheimer's disease is the subject of future research. It will also be necessary to find out whether age at the time of vaccination affects the identified relationship, as well as whether vaccination against influenza affects the rate of progression of already diagnosed Alzheimer's disease. In addition, scientists believe that it is worth studying whether there is a similar relationship between the incidence of Alzheimer's disease and the mass vaccination against the new coronavirus infection COVID-19.
Article by Bukhbinder et al. Risk of Alzheimer's Disease Following Influenza Vaccination: A Claims-Based Cohort Study Using Propensity Score Matching published in the Journal of Alzheimer's Disease.
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