高剂量流感疫苗与阿尔茨海默病风险低近55%有关？先看清这项观察性研究的边界

• New research suggests the high-dose flu shot may lower the risk of developing Alzheimer’s disease.
• Other data finds a similar link between getting vaccinated and a lower risk of dementia.
• Doctors say this may be linked to reduced inflammation, but more research is needed.

While we all know that getting a flu shot is good for you, in actuality, the matter of scheduling one and taking time out of your day can sometimes feel troublesome—especially when it seems flu season sometimes ends as soon as it begins. But now, new research suggests that getting a flu shot might offer long-lasting benefits beyond seasonal protection: It could lower your risk of Alzheimer’s.

The observational study, which was published in the journal Neurology, found a link between high-dose flu shots and a lower relative risk of developing Alzheimer's. It's a stretch to say that getting a high-dose flu shot will actually prevent dementia, but the findings join other research suggesting that staying on top of your vaccines—including the flu shot—could help to protect your brain in the long run. Here's what's behind this surprising link.

Meet the experts: Jacinta Anyaoku, MD, family medicine physician and founder of Hibiscus Aesthetics & Wellness in Katy, Texas, and Clifford Segil, DO, a neurologist at Providence Saint John's Health Center

What did the study find?

For the study, researchers analyzed data from nearly 165,000 older adults who received either a high-dose flu vaccine or a standard-dose flu vaccine. The high-dose flu vaccine contains four times the antigen (the element that creates an immune response) of the standard-dose flu vaccine, per the Centers for Disease Control and Prevention (CDC). The high-dose flu vaccine is available to adults aged 65 and up.

The researchers found that people who were 65 and older who got the high-dose vaccine had nearly a 55 percent lower relative risk of developing Alzheimer's disease over the two years they were tracked for the study.

Why might the flu shot be associated with a lower risk of Alzheimer's?

It's important to stress that the study didn't prove that getting the flu shot caused the lowered risk of developing Alzheimer's disease—it just found a link. The study also focused on older adults, making it unclear if the potential benefits extend to younger people. Still, doctors say the findings are interesting.

Previous studies have linked the flu shot to a lower risk of Alzheimer’s disease, but this was the first to compare two groups that received different flu vaccine types, points out Jacinta Anyaoku, MD, family medicine physician and founder of Hibiscus Aesthetics & Wellness in Katy, Texas. "This is significant because it helps reduce 'healthy vaccine' bias, the idea that vaccinated people are more health-conscious and engaged in their care, which could influence outcomes," she says. "In this case, both groups were vaccinated, and the group that received the high-dose vaccine showed benefit."

As for what drives this link, Dr. Anyaoku says it could be tied to inflammation. "Influenza leads to inflammation, including neuroinflammation, which could predispose the brain to changes that make Alzheimer's more likely," she says. "Getting the vaccine reduces the risk of influenza infection and therefore the associated inflammation."

The flu vaccine may also change the immune system that impacts a person's predisposition to developing Alzheimer's disease, Dr. Anyaoku says.

But there's still a lot of work that needs to be done to explore this, according to Clifford Segil, DO, a neurologist at Providence Saint John's Health Center. "Prior influenza infection is not a currently accepted pre-Alzheimer’s dementia risk factor," he says. "Most neurologists are not going to advise a flu shot to protect the brain, but will advise a flu shot to protect the lungs and general overall health."

When should you get your flu shot?

Healthcare providers typically recommend getting your flu shot before Halloween. But flu season started early this year in many parts of the country, making now a great time to get vaccinated.

There are several types of flu vaccines to consider—Dr. Anyaoku suggests looking at CDC guidelines to choose the one that makes the most sense for your needs. "The potential added benefit of reducing Alzheimer’s risk is a nice bonus, but even without it, we already have good reason to recommend the flu vaccine to older adults," she says.

Carina Hsieh, MPH, is the deputy features editor of Women’s Health. She has more than a decade’s worth of experience working in media and has covered everything from beauty, fashion, travel, lifestyle, pets, to health.

She began her career as an intern in the fashion closet at Cosmopolitan where she worked her way up to Senior Sex & Relationships Editor. While covering women’s health there, she discovered her passion for health service journalism and took a break to get her Masters in Public Health. Post-grad school, she worked as a freelance writer and as The Daily Beast’s first Beauty, Health, and Wellness Reporter.

Carina is an alum of the Fashion Institute of Technology and the Yale School of Public Health. She and her French Bulldog, Bao Bao, split their time between Brooklyn and Connecticut. She enjoys reformer Pilates, (slow) running, and smelling the fancy toiletries in boutique fitness class locker rooms.