Scientists have spent decades trying to understand why some people develop dementia while others remain mentally sharp into very old age.
Although age and genetics play important roles, researchers now know that brain health is influenced by many aspects of overall health. Conditions that affect the immune system, blood vessels, and inflammation throughout the body may also affect the brain.
A new study has added another intriguing piece to this puzzle. Researchers found that older adults who received the shingles vaccine were less likely to be diagnosed with dementia over the next four years than people who did not receive the vaccine.
The research was conducted by scientists from Brown University and several collaborating institutions and was published in Annals of Internal Medicine.
The study focused on older adults living in skilled nursing facilities. These facilities care for people who need medical supervision, rehabilitation services, or long-term support. Residents often have complex medical conditions and are considered a vulnerable population because they are generally older and have greater health risks.
The researchers analyzed electronic health records and Medicare information from more than half a million adults aged 66 and older. The participants had entered more than 5,500 skilled nursing facilities throughout the United States between 2017 and 2022.
The vaccine examined in the study was Shingrix, also known as the recombinant shingles vaccine or RZV. Shingrix became available in 2017 and is designed to protect people from shingles and its complications.
Shingles develops when the virus that causes chickenpox becomes active again later in life. The condition can cause severe pain, a blistering rash, and long-lasting nerve problems. Older adults are especially vulnerable because the immune system becomes less effective with age.
The researchers used a sophisticated approach called target trial emulation. Instead of carrying out a traditional clinical trial, they used real-world data to create conditions that closely resemble one. This method allows scientists to study large populations that might otherwise be difficult to enroll in randomized trials.
The study included 509,926 people, but only 8,843 had received at least one dose of the shingles vaccine. To make the comparison fair, the researchers included only people who had no previous dementia diagnosis and who were eligible to receive the vaccine.
The findings were striking. Over four years of follow-up, only 18.8 percent of vaccinated individuals developed dementia. Among those who did not receive the vaccine, the figure was 24.6 percent.
This difference translated into a 24 percent lower risk of dementia among vaccinated adults. According to the researchers, the findings suggest that about one in every 17 dementia cases could potentially be prevented if the vaccine itself is responsible for the lower risk.
The study supports previous research that found similar links between shingles vaccination and better brain health. Scientists are increasingly interested in the possibility that infections and immune responses may influence dementia risk.
There are several possible explanations. Preventing shingles may reduce episodes of inflammation that can affect the brain. It is also possible that the vaccine changes immune system activity in ways that indirectly protect cognitive function. Researchers are actively investigating these possibilities.
At the same time, the scientists caution against drawing conclusions too quickly. Because this was an observational study, it cannot prove cause and effect. People who received the vaccine were generally a little younger and somewhat healthier than those who remained unvaccinated. These characteristics alone may partly explain their lower risk of dementia.
The research team performed statistical adjustments to account for these differences and found that they did not fully explain the results. Nevertheless, unmeasured factors could still have influenced the findings.
The study findings are important because they suggest that a vaccine already widely available to older adults may have unexpected benefits for brain health. However, the results should be viewed as encouraging rather than definitive. More studies and clinical trials are needed to determine whether shingles vaccination can directly reduce dementia risk.
If future research confirms these findings, the shingles vaccine could become an important tool not only for preventing a painful viral disease but also for helping people maintain cognitive health as they age.
If you care about dementia, please read studies about dietary strategies to ward off dementia, and how omega-3 fatty acids fuel your mind.
For more health information, please see recent studies about Choline deficiency linked to Alzheimer’s disease, and what to eat (and avoid) for dementia prevention.
Source: Brown University.
