Older adults with no signs of dementia and at least one flu vaccination were 40% less likely to develop Alzheimer’s disease within the next four years than their unvaccinated peers, according to a new study.
Investigators used a large U.S. claims database to compare dementia outcomes in vaccinated and unvaccinated patients aged 65 years and older who had no initial evidence of brain disease. The more cumulative annual shots the patients had received, the greater their protection against Alzheimer’s, reported Paul. E. Schulz, M.D., of the University of Texas Health Science Center at Houston, and colleagues.
During follow-up appointments over four years, approximately 5.1% of flu-vaccinated cohort developed Alzheimer’s disease, compared with 8.5% of their non-vaccinated peers. There were more than 900,000 patients in each group.
Immune system a factor?
There is reason to think that the results are not due to the vaccination itself but to a protective effect related to the immune system, the authors theorized. Similar results have been found for both flu and pneumonia vaccinations in prior studies, they noted.
“Since there is evidence that several vaccines may protect from Alzheimer’s disease, we are thinking that it isn’t a specific effect of the flu vaccine,” Schulz said in a statement. “Instead, we believe that the immune system is complex, and some alterations, such as pneumonia, may activate it in a way that makes Alzheimer’s disease worse.”
Other factors also activate immune system, he added. “Clearly, we have more to learn about how the immune system worsens or improves outcomes in this disease.”
The researchers were not able to discover whether a patient’s age at vaccination would influence the results, or whether flu vaccination may affect the rate of progression of Alzheimer’s or of mild cognitive impairment.
Full findings were published in the Journal of Alzheimer’s Disease.
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This article originally appeared in the McKnight’s Clinical Daily, a joint newsletter of McKnight’s Senior Living and McKnight’s Long-Term Care News. To subscribe, check the McKnight’s Clinical Daily box at the bottom of this form.
