A surprising public health policy in Wales has helped scientists find strong evidence that a vaccine may help lower the risk of dementia.
In a new study led by Stanford Medicine, researchers found that older adults who received the shingles vaccine were 20% less likely to develop dementia over the next seven years. The findings will be published in the journal Nature.
Shingles is a painful rash caused by the same virus that causes chicken pox.
After people have chicken pox, the virus stays in their bodies and can reactivate later in life, especially in older adults, causing shingles. This virus can affect the nervous system, and scientists believe it may increase the risk of dementia.
Dementia affects over 55 million people around the world, and there are 10 million new cases each year. Alzheimer’s disease is the most common form, but scientists have not yet found a way to prevent or cure it. This has led some researchers to look at whether infections like shingles could play a role.
In past studies, people who got the shingles vaccine seemed less likely to develop dementia, but it was hard to know if the vaccine was truly the reason. That’s because people who choose to get vaccinated often have healthier lifestyles, like better diets and more exercise.
In this new study, researchers found a unique situation in Wales that helped them overcome that problem. Starting in 2013, Wales gave the shingles vaccine to people who turned 79 that year.
Those who were already 80 or older were not eligible. This rule created a natural experiment—people who were almost the same age either got the vaccine or didn’t, simply due to their birthdate.
Researchers compared the health records of people who turned 80 just before the cutoff with those who turned 80 just after. They looked at more than 280,000 older adults who did not have dementia when the vaccine program began. The two groups were almost identical in every way except for their eligibility for the vaccine.
Seven years later, people who received the shingles vaccine were 20% less likely to be diagnosed with dementia. This strong protective effect held up even when the scientists tested the data in different ways. They found no other differences between the two groups that could explain the result.
The study also found that the vaccine’s protection was stronger in women than in men. This may be because women usually have stronger immune responses to vaccines, and shingles is more common in women.
It’s still unclear how the vaccine protects against dementia. It might boost the immune system, prevent the virus from reactivating, or work in some other way. It’s also unknown if a newer shingles vaccine, which uses only part of the virus, has the same effect.
The research team has seen similar results in other countries like England, Australia, and Canada. They hope these findings will lead to more research and eventually a large clinical trial to confirm the results. Such a trial could randomly assign people to get the vaccine or a placebo and see if the vaccine truly prevents dementia.
This discovery offers hope that a simple and safe vaccine might help reduce dementia risk—something that could benefit millions of people around the world.
If you care about brain health, please read studies about inflammation that may actually slow down cognitive decline in older people, and low vitamin D may speed up cognitive decline.
For more information about brain health, please see recent studies about common exercises that could protect against cognitive decline, and results showing that this MIND diet may protect your cognitive function, prevent dementia.
The study is published in Nature.
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