Undecided about whether to get a flu shot this fall? If you’re on the fence, studies linking flu shots to diminished rates of dementia may help you make the call.
Research led by the University of Texas Health Science Center at Houston found that people ages 65 and older who received the flu vaccine have a significantly lower risk of developing Alzheimer’s than those who didn’t.
“No one seems to know exactly why this is,” Hal Scofield, M.D., a physician-scientist at the Oklahoma Medical Research Foundation. “We do know that a severe infection like the flu can cause systemic inflammation, which can travel to the brain and damage brain cells over time. So, the prevailing theory is that preventing the severe infection also protects your brain against dementia.”
In the Texas study, published in 2022, researchers examined data for nearly 1 million senior citizens nationwide, with study subjects evenly split between those who were vaccinated and those who weren’t. None showed indicators of cognitive impairment before the study began.
Researchers found that 8.5% of people who were unvaccinated developed Alzheimer’s over the next four years, compared to 5.1% of those who’d received the flu shot.
“That equates to a 40% lower risk,” said Scofield, an immunologist at OMRF who also serves as associate chief of staff for research at the Oklahoma City VA Medical Center.
A subsequent study by the same team found that a high-dose flu shot provided even greater protection against Alzheimer’s.
“For most people, the immune system becomes less effective at fighting infection around age 65,” Scofield said. “That’s why the Centers for Disease Control and Prevention recommends a high-dose flu vaccine at that age. The high-dose version is four times stronger than a regular flu shot.”
Alzheimer’s is the most common form of dementia, affecting more than 7 million Americans ages 65 and older. That number, reflecting 1 in 9 people in that age group, is expected to double by 2050.
Turns out, another vaccine also reduces dementia risk. A landmark study of health records of nearly 300,000 older adults in Wales found that those who received the shingles vaccine had a 20% lower risk of developing dementia over a seven-year follow-up period. Subsequent studies have made similar findings.
Again, scientists can’t say precisely why. However, they suspect that preventing shingles avoids nerve inflammation, blood vessel damage and micro-strokes, all of which raise the risk of cognitive decline. Like flu shots, the shingles vaccine appears to stimulate the immune system more broadly, which might help the body manage neuroinflammation more effectively.
“I suspect future studies will try to better understand this phenomenon,” Scofield said. “But the evidence seems clear: Getting vaccinated is one of the best things an older person can do to avoid dementia.”
