DAVID GREENE, HOST:
Vaccines that ward off the flu and pneumonia may also offer some protection against Alzheimer's disease. The Alzheimer's Association International Conference, which is taking place online this year, is hearing of two studies on those vaccines. And we have more from NPR's Jon Hamilton.
JON HAMILTON, BYLINE: The first study came from a team at the University of Texas that combed through millions of medical records in a national database. Albert Amran of the McGovern Medical School in Houston says the goal was to see which factors affected a person's risk of getting certain diseases, including Alzheimer's.
ALBERT AMRAN: And one of the things that came back was flu shots.
HAMILTON: That seemed odd. So Amran, a medical student, led a team that took a closer look at the medical records of about 9,000 people who are at least 60 years old. Some had received a seasonal flu shot, some hadn't.
AMRAN: We would try to make sure that both groups had an equal amount of, say, smoking status, obesity, diabetes, cardiovascular disease.
HAMILTON: Known risk factors for Alzheimer's. Then the team looked to see who was most likely to be diagnosed with the disease. Amran says people who got at least one flu shot seemed to have a lower risk.
AMRAN: We found a 17% risk reduction in our population.
HAMILTON: Also, he says...
AMRAN: More regular vaccination, so people who got the flu shot once a year, was also related to a lower incidence of Alzheimer's.
HAMILTON: Those people dropped their risk an extra 13%. Dr. Paul Schulz directs the neurocognitive disorders center at the medical school and oversaw the study. He says the results surprised him.
PAUL SCHULZ: To have these guys come out and say, well, it looks like, you know, getting the vaccine is associated with less was totally the opposite of what any of us thought.
HAMILTON: Schulz says vaccines tend to cause inflammation when they rev up the immune system. And in Alzheimer's disease, he says, inflammation is part of the problem.
SCHULZ: Here we've got a situation where we're giving them inflammation on purpose. And we're hoping it prevents the flu without causing their Alzheimer's to get worse. And we get the opposite of what we thought was going to happen. We get people who are actually doing better.
HAMILTON: A second study at the meeting didn't find as much protection from a flu shot. But it did find a benefit from another vaccine. Maria Carrillo is the chief science officer of the Alzheimer's Association.
MARIA CARRILLO: It looked at both pneumonia and flu but found more of an effect with the pneumonia vaccine.
HAMILTON: This study by a team at Duke University analyzed medical records on more than 5,000 people who were at least 65 years old. Flu shots didn't help much. But Carrillo says shots aimed at pneumococcal bacteria made a big difference.
CARRILLO: The pneumonia vaccine in people 65 to 75 actually reduced the risk of Alzheimer's by as much as 30%.
HAMILTON: Carrillo says vaccines for the flu and pneumonia may protect people by preventing diseases known to affect the brain.
CARRILLO: Every time you have one of these infections, you may actually experience a challenge to your memory and thinking.
HAMILTON: Another infection that can have a big impact on memory and thinking is COVID-19. So Carrillo says brain health may be one more reason to get a coronavirus vaccine when one arrives. Jon Hamilton, NPR News.
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