A vaccine meant to prevent shingles may also be associated with a decreased risk of dementia in older adults, according to a comprehensive U.S. study.
Researchers discovered that individuals who received the Shingrix vaccine after being admitted to a skilled nursing facility had a lower likelihood of receiving a dementia diagnosis over the subsequent four years.
The study was led by Kaley Hayes, an assistant professor at Brown University’s School of Public Health, and published in the Annals of Internal Medicine. The research involved collaboration from Brown, the University of Delaware, the Providence Veterans Affairs Medical Center, and other institutions.
Shingles is a painful condition caused by the varicella-zoster virus, the same virus responsible for chickenpox. After the initial infection, the virus can remain dormant in the body for decades, potentially reactivating later in life.
As individuals age, their immune systems may weaken, making it harder to keep the virus in check. When reactivated, shingles often results in a painful rash and can sometimes lead to persistent nerve pain.
The vaccine, Shingrix, was introduced in 2017 and has become the primary shingles vaccine used in the U.S., replacing older versions.
Scientists have shown growing interest in whether getting vaccinated against shingles might offer benefits beyond just preventing the illness. Previous studies with older vaccines suggested that vaccinated seniors also seemed less prone to developing dementia.
The new research aimed to see if the same pattern holds with Shingrix. It focused specifically on older adults entering skilled nursing facilities, who are at high risk for both shingles and cognitive decline.
The team analyzed Medicare data and electronic health records from over 5,500 facilities between 2017 and 2022. Overall, they examined 509,926 individuals aged 66 and older who hadn’t been diagnosed with dementia prior to the study period.
Only a small portion of participants received the vaccine after entering the facility. Among the total group, 8,843 individuals received at least one dose of Shingrix, while the others did not.
After four years, dementia was diagnosed in 18.8% of the vaccinated group compared to 24.6% of those unvaccinated.
Adjusting for other factors, the researchers found that vaccination was associated with a roughly 24% reduction in dementia risk. Hayes noted that this might mean about one in every 17 dementia cases could potentially be prevented if the link is causal.
The study employed a statistical approach designed to mimic the randomization of a clinical trial, making the comparisons more reliable when a traditional trial isn’t feasible.
However, such observational studies have limitations. Individuals who choose to get vaccinated may differ from those who don’t—sometimes in ways that are hard to measure, like overall health, access to healthcare, willingness to follow medical advice, or support systems at home.
In this study, vaccinated seniors were generally younger and healthier overall. The researchers adjusted for these differences, but it’s impossible to account for every variable, so the results don’t prove a direct cause-and-effect relationship.
Therefore, while the findings show a link between Shingrix and reduced dementia risk, they don’t confirm that the vaccine prevents cognitive decline. Further research is needed to understand if the relationship is truly causal.
The reasons behind this potential connection are still unclear. It’s possible that preventing shingles reduces inflammation and nerve stress that might otherwise harm brain health over time.
Additionally, the vaccine could influence the immune system in ways that are not yet fully understood, which might contribute to the observed association. These are hypotheses requiring further investigation.
This research is significant because dementia impacts millions of older Americans, affecting independence and placing a substantial burden on families and healthcare systems. Even a modest decrease in risk could be meaningful if it’s achievable through an already available vaccine.
Nevertheless, it’s important to emphasize that Shingrix is approved specifically to prevent shingles—not dementia. Patients should not expect cognitive benefits based solely on this study, and more definitive evidence is necessary before healthcare providers begin recommending it for brain health reasons.
The study received funding from GlaxoSmithKline, the manufacturer of Shingrix. The authors clarified that the company did not influence the research methods, analysis, or publication decisions. Still, this financial connection should be considered when interpreting the findings.
Overall, these results are promising but preliminary. They highlight the need for further, well-designed clinical studies to explore the link between shingles vaccination and cognitive health, moving beyond observational data to establish clear causality.
