03-04-2025
This Vaccine is Linked to a Lower Risk of Developing Dementia
While there are many theories about what causes Alzheimer's disease, one of the most well-known points to proteins called amyloid plaques. These sticky clumps are thought to build up in the brain, blocking communication between brain cells and eventually causing them to die.
But not all scientists are convinced this theory tells the whole story. In fact, a lesser-known idea is now gaining serious attention—thanks to a new study.
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Published today inNature, the study found the strongest evidence yet linking certain viruses to dementia. The good news? We may already have a vaccine that could help prevent it.
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According to the study, older adults who had the shingles vaccine were 20% less likely to develop dementia over the next seven years compared to people without the vaccine. According to the authors, this surprising finding could be the key to preventing dementia.
'It was a really striking finding,' said , an assistant professor of medicine at Stanford Medicine and senior study author. 'This huge protective signal was there, any which way you looked at the data.'
Shingles is a viral infection that creates a painful, itchy rash. The virus behind shingles, varicella-zoster, is the same virus that causes chickenpox. The virus does not clear away after chickenpox; it stays in the body for the rest of your life. However, the varicella-zoster virus is always at risk of reactivating and causing shingles.
One in three Americans will develop shingles, though the risk is even higher among older adults or those with weakened immune systems. According to the study, people vaccinated against shingles had a 37% lower risk of shingles seven years after vaccination. The finding is similar to what is seen in clinical trials since the effectiveness of the shingles vaccine wanes over time.
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For some time, scientists have suspected shingles is involved in the development of dementia. In 2024, researchers found that having a single case of shingles was associated with a20% higher riskof long-term cognitive decline.
Likewise, past studies have linked the shingles vaccine with a 17% lower risk of dementia and 164 additional days without living with a diagnosis for those who eventually got it. However, bias hampered researchers from confirming the vaccine's dementia-reducing effect. Namely, vaccinated people were usually more health conscious, so it's possible other behaviors like diet and exercise influenced their risk of dementia as well.
'All these associational studies suffer from the basic problem that people who get vaccinated have different health behaviors than those who don't,' said Geldsetzer. 'In general, they're seen as not being solid enough evidence to make any recommendations on.'
It was an accident turned opportunity for dementia researchers. To ration the shingle vaccine supply, Wales offered vaccinations only for people aged 79. The offer was only for one year; afterward, only the 78-year-olds turning 79 would be eligible next year.
Geldsetzer considered the 2013 policy change as close to a randomized clinical trial—the gold standard for experiments—as possible. '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 said.
Scientists were now in a position to study the vaccine effects by comparing dementia rates among 80-year-olds just before the policy shift (and ineligible for vaccination) and those who turned 80 afterward.
'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 explained. 'They are similar to each other apart from this tiny difference in age.'
For over seven years, the researchers looked at the health records of over 280,000 older adults, paying close attention to those one week apart from turning 80.
One in eight older adults, now 86 and 87, were diagnosed with dementia. People vaccinated against shingles had a 20% lower chance of developing dementia compared to the unvaccinated.
No other factors, such as level of education or health conditions, explained the dementia risk difference—just the vaccine. 'The signal in our data was so strong, so clear and so persistent,' Geldsetzer said. The authors suggest the shingles vaccine possibly reduces dementia by providing a broader immune response or by stopping the dormant virus from reactivating.
Related: How Vision Loss Can Predict Dementia 12 Years Earlier
The vaccine appeared to be more effective in protecting women than men against dementia. According to Geldsetzer, the differences in vaccine response could come from women typically having high antibody responses to vaccination, especially as shingles is more common in women than men. Another explanation is that dementia might develop differently in women than men—a theory still under investigation.
The next step for researchers is a larger clinical trial to see the effects of the shingles vaccine on dementia and how it preserves cognition. In the meantime, people don't have to wait 10 or 20 years for ways to prevent dementia. A shingles vaccine is already available.
Up Next:"A natural experiment on the effect of herpes zoster vaccination on dementia." Nature.
Pascal Geldsetzer, MD, Ph.D, assistant professor of medicine at Stanford Medicine
"About Shingles (Herpes Zoster)." Centers for Disease Control and Prevention.
"Herpes zoster and long-term risk of subjective cognitive decline." Alzheimer's Research & Therapy.
"The recombinant shingles vaccine is associated with lower risk of dementia." Nature Medicine.
