These 8 drugs could help fight dementia - and they're already on the market

MW These 8 drugs could help fight dementia - and they're already on the market

By Brett Arends

The findings have been tested in the real world

Getting yourself vaccinated against shingles doesn't just protect you against that painful and debilitating disease - it may also slash your risk of developing Alzheimer's by as much as 20%, according to a recent study involving hundreds of thousands of people.

And that finding, based on the closest thing you can get to gold-standard methodology in the real world, is among the reasons that a worldwide group of scientists have placed the shingles vaccine at the head of a list of drugs already on the market that they want studied in more detail for their possible benefits in the war on dementia.

(The tests used the older shingles vaccine Zostavax $(MRK)$, since replaced by the newer Shingrix - more on that below.)

Among the other drugs were Viagra $(PFE)$, the famous blue pills used to treat erectile dysfunction; riluzole, a drug used to treat ALS, or Lou Gehrig's disease; Gilenya (fingolimod) $(NVS)$, a treatment for relapsing-remitting multiple sclerosis; and Trintellix (vortioxetine) $(TAK)$ (JP:4502), an antidepressant.

The new report, published in the peer-reviewed academic journal Alzheimer's Research & Therapy, involved medical experts and researchers in dementia from the National Institutes of Health in Baltimore, the Icahn School of Medicine at Mount Sinai in New York, the University of Nevada in Las Vegas, and the Medical University of South Carolina in Charleston, S.C., plus the National University of Singapore, the University of Exeter and King's College London in the U.K., McGill University and the University of Calgary in Canada, the University of Toulouse-Jean Jaurès in France, and the University of Stavanger in Norway.

It addresses a huge and growing public-health crisis that is often underappreciated. If you are 55 or over there is a 42% chance you will get dementia before you die, researchers now estimate. Nearly 7 million Americans have dementia - the actor Bruce Willis, who has frontotemporal dementia, is merely the most famous - and as many as 57 million people worldwide.

The expert panel in total identified eight drugs already on the market that may help fight or prevent dementia, and which they say merit further investigation. (As all dementia is already irreversible and fatal, you'd think rolling out human trials would be fast and easy - the downside is limited.)

Among them is the erectile-dysfunction pill Viagra (medical name: sildenafil). It was first tested in the 1980s as a treatment for angina, the heart disease, and it is currently used for treatment of pulmonary hypertension as well as ED. Researchers cited various medical mechanisms by which the drug could help prevent Alzheimer's or other dementias. Two large studies based on health-insurance databases found that those who took Viagra had a lower risk of developing Alzheimer's. But another study based on Medicare data called those findings into question.

More importantly, say medical experts, the studies may be confused by so-called confounding factors, meaning that there may be other factors at play.

For example, they note, it could also be that the people taking Viagra are also having more sex as they get older - and it's the sex, not the Viagra, that is cutting their risk of developing dementia.

Or it may not even be the sex, per se, which protects against dementia but the broader benefits of a romantic relationship, experts say. For example, older people who don't take Viagra are more likely to be living alone and isolated. Those factors, rather than the lack of blue pills, may be raising their risks of dementia.

This is what makes the data on the shingles vaccine so compelling, says Nicholas Doher, a neurologist at the Cleveland Clinic and a specialist in memory and cognitive disorders. The evidence on the shingles vaccine and dementia comes from the equivalent of a gold-standard natural experiment where the influence of such confounding variables has been minimized, he says.

The government of Wales made free shingles vaccines available 13 years ago to everyone in the population under the age of 80 and born after a specific date. More than half of those eligible took up the offer. By comparing those born immediately after the cutoff date, who could take the vaccine, with those born immediately before that date, they had a near-perfect experiment involving up to tens of thousands of people.

Those taking the shingles vaccine saw a 20% collapse in their risk of getting dementia within the next seven years. (They also saw a 37% collapse in their risk of getting shingles.)

Other studies found similar conclusions regarding the vaccine and dementia.

The Welsh results involved the older shingles vaccine, Zostavax, which has since been replaced in widespread use by GSK's $(GSK)$ Shingrix. But that may not matter, says Doher at the Cleveland Clinic; there is "good reason" to think the newer vaccine will work as well or better against dementia, he says. "Shingrix is very much superior in terms of effectiveness and duration of benefit," he told MarketWatch.

The bottom line? Looking across the range of drugs that could help prevent or slow Alzheimer's, the panel thinks the shingles vaccine has the highest possibility of providing "a substantial benefit at the population level for prevention," while Viagra and riluzole may have benefits as treatments for those with dementia, especially in its earliest stages.

-Brett Arends

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March 07, 2026 10:00 ET (15:00 GMT)

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