June 30, 2022 – For older adults, getting the annual flu shot may do more than protect against the flu. It may also reduce the risk of getting Alzheimer’s disease.
In a large study of vaccinated and unvaccinated adults ages 65 and older, those who received at least one influenza vaccine were less likely than unvaccinated peers to get Alzheimer’s over the course of 4 years.
But it’s not a one and done. The strength of the protective effect increased with the number of years that a person received an annual flu shot, such that the rate of developing Alzheimer’s was lowest in people who consistently got the flu vaccine every year.
"Influenza infection can cause serious health complications, particularly in adults 65 and older," says Avram Bukhbinder, MD, with UTHealth in Houston.
"Our study's findings – that vaccination against the flu virus may also reduce the risk of Alzheimer's dementia for at least a few years – adds to the already compelling reasons to talk with your doctor about getting the flu vaccine annually," he says.
This study "suggests that flu vaccination may be valuable for maintaining cognition and memory as we age. This is even more relevant today in the COVID-19 environment," says Heather Snyder, PhD, with the Alzheimer's Association.
More than 6 million Americans are living with Alzheimer's. By 2050, this number is projected to rise to nearly 13 million, according to the Alzheimer’s Association.
The Houston researchers compared the risk of Alzheimer’s in roughly 935,000 flu-vaccinated adults and a similar number of non-vaccinated adults ages 65 and older.
Over the course of 4 years, about 5% of flu-vaccinated adults got Alzheimer’s disease, compared to around 9% of adults who weren’t vaccinated.
The risk of getting Alzheimer’s disease was 40% lower in the vaccinated group.
The apparent protective effect on dementia may not be specific to the flu vaccine. Past studies have found ties between other adult vaccinations – including those for tetanus, polio, herpes, and pneumonia – and a lower risk of dementia.
And as more time passes since the introduction of the COVID-19 vaccine, it will be worth investigating whether a similar association exists between COVID-19 vaccination and a lower risk of Alzheimer’s disease, the researchers say.
Snyder cautions that it’s "too early to tell if getting flu vaccine, on its own, can reduce risk of Alzheimer’s. More research is needed to understand the biological mechanisms behind the results in this study."
"For example, it is possible that people who are getting vaccinated also take better care of their health in other ways, and these things add up to lower risk of Alzheimer’s and other dementias," Snyder says. "It is also possible that there are issues related to unequal access and/or vaccine hesitancy and how this may influence the study population and the research results.”