Shingles Vaccine Linked to Reduced Dementia Risk in Older Adults
A growing body of evidence suggests that the shingles vaccine may offer significant protection against dementia for older adults.
The exact mechanism is still under investigation, but it likely relates to effects on the nervous system. Shingles results from the reactivation of the varicella-zoster virus, leading to inflammation in the brain, as explained by Dr. Jennifer Pauldurai, the medical director at Inova Brain Health and Memory Disorders Program in Virginia.
Having had chickenpox increases the risk of developing a painful shingles rash later in life; postherpetic neuralgia, a form of chronic pain, is the most common complication stemming from this condition since the virus remains dormant in the peripheral nervous system.
It’s important to clarify that the shingles vaccine isn’t a “magic pill,” Pauldurai noted. Instead, it serves as a preventive measure against a disease known to negatively affect brain health.
When the brain faces stress or illness, underlying risks associated with dementia become more pronounced, Pauldurai explained. Essentially, shingles could elevate the chances of dementia if the brain is compromised due to illness.
A study published on June 16 in the Annals of Internal Medicine indicates that up to 1 in 17 cases of dementia could potentially be prevented through shingles vaccination. Among over 509,000 nursing facility patients aged 66 and older, those who received the shingles vaccine within a year of admission faced a 5.8% lower risk of developing dementia over four years.
“That’s noteworthy,” remarked Kaley Hayes, the study’s lead author and an associate director of pharmacoepidemiology at Brown University, who expressed surprise at the level of protection observed.
Similar findings have emerged from international research. A study of over 282,000 older adults in Wales published last year in Nature showed a 3.5% reduction in dementia risk associated with shingles vaccination over seven years.
Research from Australia involving over 101,000 adults also confirmed a 1.8% lower dementia risk linked to vaccine eligibility over 7.4 years. Additionally, a Canadian study from February found a similar 2% reduction in risk over 5.5 years among more than 232,000 older adults.
Considering the vast number of individuals who have had chickenpox—over 99% of those born in 1980 or earlier, according to the CDC—it’s notable that shingles impacts around 1 million people in the U.S. each year.
Previous studies have shown a connection between shingles and increased dementia risk. For instance, research published last year in the Journal of Prevention of Alzheimer’s Disease found that older adults hospitalized for severe shingles had a 13% higher risk of dementia compared to the general population.
Link Between Shingles and Alzheimer’s Proteins
The risk for shingles tends to increase with age, primarily due to the immune system’s natural decline. When reactivated, the shingles virus might also lead to the buildup of amyloid and tau proteins in the brain, both associated with Alzheimer’s disease, according to Dr. Timothy Chang from UCLA.
Chang suggested that the shingles vaccine might enhance overall immunity, thereby reducing neuroinflammatory issues as well.
Interestingly, research indicates that the shingles vaccine is associated with a lower risk of dementia compared to the flu and Tdap vaccines.
“If you were on the fence about getting vaccinated, this may be a strong reason to do it,” Chang said.
Shingles is also linked to higher risks of heart disease and stroke, which might further explain the vaccine’s protective effect on brain health, Hayes noted.
“Reduced oxygen to the brain is closely tied to cognitive function,” she explained. “Even subclinical viral activity might cause micro-damage to cerebral arteries.”
Potential Gender Differences in Vaccine Efficacy
In the U.S., individuals aged 50 and older can receive two doses of Shingrix, the sole FDA-approved shingles vaccine. The single-dose Zostavax, which was less effective, was discontinued in 2020.
The CDC still recommends Shingrix for people who have received the chickenpox vaccine or previously had shingles, irrespective of prior Zostavax vaccination.
Although Hayes’ work focused on Shingrix, much of the related research revolved around Zostavax. Ann Philbrick from the University of Minnesota College of Pharmacy expressed optimism over Shingrix’s potential neuroprotective benefits, while noting the effects seemed less pronounced in men.
In Hayes’ research, the correlation between Shingrix and reduced dementia risk was weaker among men compared to women, reflecting possible biological differences in vaccine response.
Philbrick pointed out that people who opt for recommended vaccinations tend to be more health-conscious, implying that those who receive the shingles vaccine might start off with a lower baseline risk for dementia.
Despite these considerations, Hayes emphasized that her team accounted for various limitations, and their observational study was fashioned to replicate the design of a randomized controlled trial, the gold standard in research.
Studies in Canada and Australia were structured to minimize bias, examining individuals eligible for vaccination based solely on birth dates rather than those who actually received the vaccine.
Vaccine Uptake Concerns
For Philbrick, the most striking aspect of Hayes’ study was the unsettling revelation that fewer than 2% of nursing facility patients, already vulnerable in health, had received even one dose of Shingrix.
According to CDC records, only about one-third of U.S. adults aged 50 and older and roughly 43.8% of those over 60 had received at least one dose of any shingles vaccine by 2022, with lower rates among Black and Hispanic adults compared to their white counterparts.
While Shingrix is often covered by Medicare Part D and Medicaid, and insurance providers usually cover it, Philbrick noted that practical access can hinder vaccine uptake.
“It takes an extra effort—like scheduling an appointment and remembering to come back for the second dose,” she said.
Pauldurai indicated that patients often inquire about ways to prevent dementia, suggesting that while it’s not a replacement for sound lifestyle practices, getting the shingles vaccine could be beneficial for brain health.
“It’s like wearing a helmet when you ride a bike—you take precautions to limit risks,” Pauldurai remarked.
