En español | The flu shot may do more than keep you from getting a fever and fatigue this winter. New research shows that the annual vaccine could pack brain health benefits, as well.
A study presented at this year's virtual Alzheimer's Association International Conference (AAIC) analyzed the health records of more than 9,000 adults age 60 and older and found that having at least one flu vaccine was associated with a 17 percent reduced incidence of Alzheimer's disease. What's more, adults who received the vaccination more often — say, annually, compared with just once or twice — had an even greater drop in dementia risk.
"The more frequently you got it, the more of a reduced risk you had,” says Albert Amran, a medical student at McGovern Medical School at the University of Texas Health Science Center in Houston and the presenting author of the study.
Further research is needed to better understand what could be causing this association between the vaccine and a reduced incidence of Alzheimer's disease in older adults. It could be that the vaccine gives a routine boost to the immune system, which weakens with age, Amran suggests. (The role that bacterial and viral infections play in the cause and progression of Alzheimer's disease is one that researchers in the brain health field are studying.)
It may also be that people who keep up with their flu shots “take care of themselves in other ways” and engage in habits that are known to keep the brain healthy, says Rebecca Edelmayer, director of scientific engagement at the Alzheimer's Association. Exercise, diet and sleep have all been shown to reduce risk of cognitive decline in adults. Intensive blood pressure control can also lower risks for mild cognitive impairment (MCI) — a precursor to dementia.
"So we have to do more research to understand if it's more of an indirect effect regarding better management of health, or potentially some other type of factor,” Edelmayer adds.
Pneumonia vaccine may lower Alzheimer's risk
A second paper presented at AAIC 2020 found that the pneumonia vaccine — another common shot recommended for older adults — could also offer protective qualities when it comes to dementia.
A team of researchers led by Svetlana Ukraintseva, associate research professor in the Social Science Research Institute at Duke University, studied the medical records of more than 5,100 older adults and discovered that people who got pneumonia vaccines between the ages of 65 and 75 had a lower prevalence of Alzheimer's disease. The association was especially strong (up to 40 percent risk reduction) in individuals who did not carry a genetic risk factor for Alzheimer's. Adults between 65 and 75 years old who got vaccinated against pneumonia and the flu experienced a lower risk of Alzheimer's disease later in life; however, the effect was not seen for the flu shot alone.
"This suggests that adult vaccination against pneumonia may reduce Alzheimer's disease risk depending on individual genotype, which supports personalized prevention of Alzheimer's disease,” Ukraintseva wrote in an email to AARP.
'Another reason’ to get the shot this year
Public health experts have long preached the importance of the flu vaccine, and this year that cry is louder than ever, with coronavirus cases surging in many areas of the country and flu season fast approaching. Flu vaccines will not provide protection against a coronavirus infection, the Centers for Disease Control and Prevention (CDC) says, but they will reduce the strain on hospitals already strapped for resources during the pandemic. And Amran says the latest research highlighting the potential brain benefits of the vaccine “just may be another reason to go ahead” and get the flu shot this year.
"With the COVID-19 pandemic, vaccines are at the forefront of public health discussions. It is important to explore their benefit in not only protecting against viral or bacterial infection but also improving long-term health outcomes,” Maria C. Carrillo, chief science officer at the Alzheimer's Association, said in a statement.
"It may turn out to be as simple as if you're taking care of your health in this way — getting vaccinated — you're also taking care of yourself in other ways, and these things add up to lower risk of Alzheimer's and other dementias,” she added.
The CDC recommends that most people 6 months and older get a flu vaccine every season; the pneumococcal vaccine is typically recommended for adults 65 and older and for people with certain medical conditions.