Getting this vaccine lowered seniors’ dementia risk by 20%

Most people know that exercising, eating healthy and keeping your mind active can lower your risk of dementia.

But with the expected number of Americans living with dementia projected to increase to 13.8 million by 2060, the hunt is on for anything that could help prevent this devastating disease.

Now, a new study out of Stanford Medicine has presented some of the strongest evidence yet that a vaccine that can help prevent dementia already exists — except it’s for a totally different condition.

Researchers analyzed the health records of over 280,000 older adults in Wales and found that those who received the shingles vaccine were 20% less likely to develop dementia over the next seven years compared to those who did not.

“It was a really striking finding,” Dr. Pascal Geldsetzer, an assistant professor of medicine at Stanford, said. “This huge protective signal was there, any which way you looked at the data.”

Shingles is a painful rash condition that is caused by the reactivation of the varicella-zoster virus — which remains dormant in nerve cells after someone has chickenpox.

While the exact cause of the association between the shingles vaccine and dementia is unknown, some believe preventing this reactivation might reduce neuroinflammation, a factor implicated in the development of dementia.

The study is unique in a major way. Previous research has shown a link between the shingles vaccine and dementia — for example, a 2024 study by the University of Oxford found that the newer recombinant shingles vaccine, Shingrix, was associated with a 17% reduction in dementia risk compared to its predecessor, Zostavax.

However, research not been able to account for the impact that lifestyle factors might have on the results.

“All these associational studies suffer from the basic problem that people who get vaccinated have different health behaviors than those who don’t,” Geldsetzer said.

“In general, they’re seen as not being solid enough evidence to make any recommendations on.”

Notably, this study capitalized on a unique public health policy in Wales, in which people who had turned 80 just after September 1, 2013 were eligible for the shingles vaccine — while those who turned 80 just before were ineligible.

This natural division allowed researchers to compare dementia rates between two very similar groups.

“We know that if you take a thousand people at random born in one week and a thousand people at random born a week later, there shouldn’t be anything different about them on average,” Geldsetzer said. “They are similar to each other apart from this tiny difference in age.”

“What makes the study so powerful is that it’s essentially like a randomized trial with a control group — those a little bit too old to be eligible for the vaccine — and an intervention group — those just young enough to be eligible,” he added.

Even when accounting for other factors — such as education levels and vaccination history — the team found the two groups to be virtually indistinguishable apart from the drop in dementia cases in the shingles vaccine cohort.

“Because of the unique way in which the vaccine was rolled out, bias in the analysis is much less likely than would usually be the case,” Geldsetzer said. “The signal in our data was so strong, so clear and so persistent.”

As with the Oxford study, this new study found that the vaccine’s protective benefits were higher among women than men — possibly because women are more prone to shingles.

The Stanford team has replicated the study in several other countries over the last two years with similar results.

They are now hoping to launch a large, randomized controlled trial to strengthen the evidence.

“It would be a very simple, pragmatic trial because we have a one-off intervention that we know is safe,” Geldsetzer said.

Can other jabs fight dementia?

Interestingly enough, this isn’t the only vaccine that has been shown to lower dementia risk. UTHealth Houston found in 2023 that vaccination against tetanus and diphtheria were also linked to a a reduced risk for Alzheimer’s.

The year before, the same research team published another study that found that getting at least one flu vaccine made people 40% less likely to develop Alzheimer’s disease that those who had never gotten a flu jab.

“We and others hypothesize that the immune system is responsible for causing brain cell dysfunction in Alzheimer’s,” said  Dr. Paul E. Schulz, senior author of the paper.

“The findings suggest to us that vaccination is having a more general effect on the immune system that is reducing the risk for developing Alzheimer’s.”