Can the Flu Vaccine Lower Dementia Risk?

Dementia, i.e., impairment in memory, language, thinking, and problem-solving abilities, affects a significant number of elderly people. Alzheimer’s disease is one common cause, but there also are other diseases that can lead to dementia. The dementia risk can be related to a variety of factors that include lifestyle aspects, chronic diseases, traumatic brain injury, or pollution, for example. Reducing the risk of developing dementia is a goal for public health. There has been evidence that vaccinations commonly used in adults, such as influenza or tetanus vaccines, could lower the risk of developing dementia. However, existing studies are limited in scope and further investigations are needed.

Timothy L. Wiemken, Saint Louis University, MO, USA, and colleagues have performed an analysis of data from a large group of U.S. veterans to find associations between influenza vaccinations and dementia risk. The team used medical records collected over a ten-year period from patients over 65 years of age with no known dementia before the study period. The analysis included ca. 67,000 individuals with influenza vaccinations and ca. 57,000 without. Due to the source of the data, the patients were mostly male, with 3.8 % female subjects. The team checked the records for the number of influenza vaccine doses and dementia diagnoses, as well as other factors that could influence dementia risk, such as demographics, geographic data, and comorbidities.

The team found that patients with six or more influenza vaccinations had a 12 % lower risk for dementia compared with those without any influenza vaccinations. According to the researchers, this result is consistent with existing hypotheses stating that vaccinations may reduce the risk of dementia by training the immune system and generating non-specific protection. The team points out that the results may not transfer to other countries and healthcare systems and that the mechanisms that could underlie the observed correlations are still speculative. In addition, factors such as social support or connections between a healthier lifestyle and the number of vaccinations were not considered in the study. However, if vaccines were confirmed to contribute to a lower dementia risk, they could provide a useful low-cost public health measure—in addition to their protective effect against infectious disease.