Study suggests shingles vaccine may lower dementia risk

PROVIDENCE, R.I. [Brown University]-Older adults who received a shingles vaccine after a stay in a skilled nursing facility had a 24% lower risk of being diagnosed with dementia over a four-year period than those who were not vaccinated, according to a new study.

The findings are based on an analysis of health records and Medicare data 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 those who received at least one dose of the recombinant shingles vaccine, known as RZV or Shingrix, with those who did not. The vaccine was introduced in 2017 and is the only shingles vaccine currently on the market.

"A lot of previous studies with similar results focused on an older vaccine," said study author Kaley Hayes, an assistant professor at Brown University's School of Public Health. "This study looks at the newest vaccine only in an older, vulnerable adult population who were not up to date with shingles vaccination and are at a very clear clinical point in care: entering a skilled nursing facility."

The findings align with several earlier studies that focused on a prior shingles vaccine have linked shingles vaccination to a lower risk of dementia.

"It fits into this large puzzle that's just starting to come together that the vaccines are effective at preventing shingles and also appear to have neuroprotective benefits as well," said Hayes, who is also the associate director of pharmacoepidemiology for Brown's Center for Gerontology and Healthcare Research.

Hayes led the study published in Annals of Internal Medicine alongside colleagues from Brown, the University of Delaware, the Providence Veterans Affairs Medical Center and other institutions.

To analyze the data, the team used a method known as a target trial emulation, which is designed to mimic the conditions of a randomized clinical trial when conducting one is not practical. The study included Medicare claims and electronic health record information from patients admitted to more than 5,500 skilled nursing facilities across the country between 2017 and 2022. Only 8,843 of 509,926 participants received the vaccine.

To be included in the study, patients could not have a prior diagnosis of dementia and had to be eligible to receive the shingles vaccine. After a four-year follow-up, the team found that people who received at least one of the two doses of Shingrix had a substantially lower risk of being diagnosed with dementia than those who did not receive the vaccine. According to the data, only 18.8% of vaccinated adults developed dementia within four years compared with 24.6% of those who were not vaccinated.

"This translates to about one in 17 dementia cases potentially being prevented," Hayes said.

The primary caveat of the study is the researchers cannot say for certain that the vaccine was the reason that vaccinated adults developed dementia at a lower rate. People who got vaccinated, for instance, tended to be slightly younger and healthier than those who did not, which may have also lowered their dementia risk. The research team adjusted for those differences and found that those factors did not fully account for the association. More research, including clinical trials, will ultimately be needed to determine whether the vaccine directly reduces the risk of dementia.

The researchers say the results point toward a generally accessible tool that can help both protect the body and mind.

"Our cognition is so tied to our overall health and what happens to us physically," Hayes said. "It's really amazing to see that something that's supposed to prevent a physical ailment can also help keep our brain healthy, too."

In the study, the authors acknowledged funding from GlaxoSmithKline, which makes the shingles vaccine Shingrix, noting that the company had no control over the study design, analysis or decision to publish the results.