People who received at least one flu vaccine were 40% less likely to develop Alzheimer’s disease over four years than their unvaccinated counterparts, according to a new study from the University of Texas.

Previous studies have already shown that, in addition to the flu vaccine, there is a reduced risk of dementia associated with receiving a variety of adult vaccines, including tetanus, polio and herpes vaccines.

Alzheimer’s disease affects more than 6 million people in the United States, and the number of people affected is increasing as the country’s population ages.

Researchers compared the risk of Alzheimer’s disease between patients with and without prior flu vaccination in a large national sample of US adults aged 65 and older.

An early online version of their study detailing the results was made available ahead of publication in the August 2 issue of the Journal of Alzheimer’s Disease.

“We found that vaccinating older adults against influenza reduced the risk of developing Alzheimer’s disease. The likelihood of developing Alzheimer’s disease was lowest among those who received the flu vaccine continuously every year. Future research should investigate whether the flu vaccine is associated with symptom progression in patients who already have dementia with Alzheimer’s disease,” the team concluded.

During four years of follow-up, about 5.1% of patients vaccinated against influenza developed Alzheimer’s disease.

Meanwhile, the rate for unvaccinated patients was 8.5%.

According to the researchers, the results support the strong protective effect of the flu vaccine against Alzheimer’s disease. However, the mechanisms of action behind this process need further study.

Source: The University of Texas Health Science Center at Houston