Older adults who received the shingles vaccine after entering a skilled nursing facility were less likely to be diagnosed with dementia over the next four years, according to a new study. The researchers found that vaccinated adults had a 24% lower risk of dementia compared to those who did not receive the vaccine.
The analysis was based on Medicare data and medical records from more than 500,000 adults age 66 and older who were admitted to skilled nursing facilities for short- or long-term care. Researchers compared patients who received at least one dose of the recombinant shingles vaccine, known as RZV or Shingrix, with patients who were not vaccinated. Shingrix was introduced in 2017 and is currently the only shingles vaccine available on the market.
Studying the newest shingles vaccine
“Many previous studies with similar results focused on an older vaccine,” said study author Kaley Hayes, an assistant professor at Brown University School of Public Health. “This study looks at the newer vaccine only in a population of older, vulnerable adults who were not up to date on the shingles vaccine and are at a very clear clinical point of care: entering a skilled nursing facility.”
The results are consistent with several previous studies involving a previous shingles vaccine that also found an association between shingles vaccination and a reduced risk of dementia.
“It fits into this big puzzle that is just beginning to be solved that vaccines are effective in preventing shingles and also appear to have neuroprotective benefits,” said Hayes, who is also associate director of pharmacoepidemiology at Brown’s Center for Gerontology and Healthcare Research.
Hayes led the study, published in Annals of internal medicinewith researchers from Brown, the University of Delaware, the Providence Veterans Affairs Medical Center and other institutions.
More than 500,000 older adults analyzed
The researchers used a technique called target test emulation to analyze the data. This approach attempts to recreate some of the conditions of a randomized clinical trial in situations where conducting such a trial is not practical.
The study included Medicare claims and electronic medical records from patients admitted to more than 5,500 skilled nursing facilities nationwide between 2017 and 2022. Of the 509,926 people included in the analysis, only 8,843 received the shingles vaccine.
Participants had to be eligible for the shingles vaccine and not have been previously diagnosed with dementia.
After four years of follow-up, adults who had received at least one of the two doses of Shingrix were substantially less likely to receive a dementia diagnosis. Dementia developed in 18.8% of vaccinated participants, compared to 24.6% of those who were not vaccinated.
“This translates to approximately one in 17 cases of dementia being preventable,” Hayes said.
The study cannot prove cause and effect
A major limitation is that researchers cannot determine with certainty whether Shingrix itself was responsible for the lower rate of dementia diagnoses.
People who received the vaccine tended to be slightly younger and healthier than those who were not vaccinated, differences that could also contribute to a lower risk of dementia. The researchers adjusted their analysis to account for these factors and found that they did not fully explain the association.
Additional research, including clinical trials, will be needed to establish whether the shingles vaccine directly reduces the risk of developing dementia.
The researchers say the findings suggest that an already widely accessible preventative measure could potentially benefit both physical and cognitive health.
“Our cognition is very tied to our overall health and what happens to us physically,” Hayes said. “It’s really surprising to see that something that is supposed to prevent a physical ailment can also help keep our brain healthy.”
The authors reported receiving funding from GlaxoSmithKline, the maker of Shingrix. They noted that the company had no control over the study design, analysis or the decision to publish the findings.