New research indicates that seniors who receive the shingles vaccine after moving into a skilled nursing facility are less likely to be diagnosed with dementia over the next four years.
The study found that vaccinated individuals had approximately a 24% reduced risk compared to those who were not vaccinated.
Led by Kaley Hayes from Brown University’s School of Public Health, the study was published in the Annals of Internal Medicine. The research team included experts from the University of Delaware, Providence Veterans Affairs Medical Center, and other institutions.
Shingles results from the reactivation of the varicella-zoster virus, which also causes chickenpox. After recovery from chickenpox, the virus can lay dormant in nerve tissues for years and may reactivate later in life, particularly in older adults.
Reactivation leads to shingles, which often causes a painful skin rash and can sometimes result in prolonged nerve pain. Since the risk increases with age, vaccination is widely recommended for older populations.
The current shingles vaccine, known as Shingrix, was introduced in 2017. It is a recombinant vaccine that does not contain live virus, and it currently is the only shingles vaccine available in the United States.
Previous studies suggested that older shingles vaccines might be linked to a reduced risk of dementia. This new research focused specifically on Shingrix and on a particularly vulnerable group — seniors entering skilled nursing facilities.
The team analyzed Medicare claims and electronic health records from over 5,500 nursing homes nationwide. They included 509,926 adults aged 66 and older who had no prior dementia diagnosis and were eligible for the shingles vaccine.
Of these, only 8,843 received at least one dose of Shingrix after entering a facility, while the rest remained unvaccinated during the study period.
After four years, 18.8% of those vaccinated were diagnosed with dementia, compared to 24.6% of those unvaccinated.
The researchers estimated that this difference reflects approximately a 24% lower risk of developing dementia among vaccinated individuals. Hayes noted that roughly one case of dementia could potentially be prevented for every 17 cases that might occur without vaccination.
To improve the reliability of their findings, the scientists used a method called target trial emulation. This approach tries to create a comparison similar to a randomized clinical trial by carefully matching similar individuals and adjusting for known differences.
This matter because conducting a true randomized trial with hundreds of thousands of nursing home residents would be impractical and costly. Still, observational studies cannot fully eliminate biases, such as differences in health status between those who choose vaccination and those who do not.
For example, vaccinated participants tended to be slightly younger and healthier, which could partly explain their lower dementia rates. Even after adjusting for these factors, the association persisted, but causation cannot be confirmed.
Scientists are exploring potential reasons why shingles vaccination might influence brain health. One theory suggests that preventing shingles reduces systemic inflammation or neural stress, but this remains unproven.
Another idea is that the vaccine could modulate the immune system in ways that support brain function. Additional research is needed to clarify these possibilities.
The findings are significant because dementia poses a major health challenge among older adults, and effective prevention methods are limited. If an existing vaccine also offers brain protection, it could have meaningful public health implications.
However, caution is warranted. The study was observational and not designed to prove that the vaccine directly prevents dementia. It also relied on health records that might miss some diagnoses or differences in healthcare access.
The research was funded by GlaxoSmithKline, the manufacturer of Shingrix. Although the authors report that the company had no influence over study design or publication decisions, this financial relationship should be acknowledged.
Overall, the research adds to growing evidence that shingles vaccination could be associated with a lower incidence of dementia. While promising, more rigorous studies, such as randomized clinical trials, are needed before making definitive claims about prevention.
Source: KSR.