- Dementia currently affects more than 57 million people worldwide, and numbers are projected to almost triple over the next 25 years.
- Many factors can increase a person’s risk of developing dementia, including age, genetics, vascular diseases and, according to newer research, some viral infections.
- One viral infection linked to an increased risk of dementia is shingles, caused when a dormant chicken pox virus reactivates in nerve cells.
- New research suggests that vaccination against shingles could reduce the risk of dementia by 20%.
- If these findings are verified, shingles vaccination could be a cost-effective way of slowing the rapid increase in dementia cases.
Globally, the number of people affected by
The Centers for Disease Control and Prevention (CDC)
Research has shown that viral infections, particularly those that affect the nervous system, are associated with an increased risk of dementia.
Now, a study led by scientists from Stanford Medicine, published in
The researchers suggest this provides further evidence of the link between viral infection and dementia, and that the vaccine could be a cost-effective way of reducing the risk of dementia.
Courtney M. Kloske, PhD, Alzheimer’s Association director of Scientific Engagement, not involved in this study, commented for Medical News Today that:
“This new study adds to our current knowledge by suggesting the shingles vaccine may also reduce someone’s risk of developing dementia. These new results, while preliminary, call for further studies in large, diverse study populations to inform public health strategy regarding whether vaccinations can decrease our risk of developing dementia as we age.”
The study took advantage of a health policy in Wales which, on September 1, 2013, introduced the shingles vaccine, using a live-attenuated (weakened) form of the virus.
The health authority offered the vaccine to all 79-year-olds (born on or after September 1, 1933), but anyone born before September 1, 1933 was not eligible.
By selecting those born one week either side of September 1, 1933, the researchers had two age-matched groups of people, one of which had received the shingles vaccine and one which had not.
Senior author on the study, Pascal Geldsetzer, MD, PhD, MPH, assistant professor of medicine at Stanford University, said in a press release that “[w]hat makes the study so powerful is that it’s essentially like a randomized trial with a control group — those a little bit too old to be eligible for the vaccine — and an intervention group — those just young enough to be eligible.”
The researchers compared the health outcomes of both groups for the next 7 years. About half of those eligible for the vaccine received it, compared with almost none of those not eligible. In their analysis, they allowed for the fact that not everyone who was eligible for the vaccine received it.
During the 7 year follow up, of the 296,324 people in the sample, 14,465 had at least one diagnosis of shingles. Those who had received the vaccine had a 37.2% lower relative risk of getting shingles than those were unvaccinated.
In this study, the researchers did not differentiate between different types of dementia. A person was recorded as having dementia if there was a new diagnosis of dementia in the electronic health record data, or if dementia was listed on their death certificate as a primary or contributory cause of death.
A total of 35,307 people were newly diagnosed with dementia during the 7-year follow-up period.
Of these, people who had received the shingles vaccine were 3.5% less likely to receive a dementia diagnosis, which corresponds to a relative reduction of 20%.
Steven Allder, MD, consultant neurologist at Re:Cognition Health, not involved in this research, told MNT that:
“The findings strengthen the case for encouraging shingles vaccination in older adults. If further research confirms the link between the vaccine and lower dementia risk, it could make vaccination an even more compelling public health strategy. Given the high economic and social costs of dementia care, a relatively inexpensive vaccine could prove to be a cost-effective preventive measure.”
The effect of the vaccination on dementia risk differed markedly between the sexes, with a much greater reduction in new diagnoses of dementia in women than men.
This was seen despite the vaccination having similar effects on diagnoses of shingles and
“This could be due to biological differences in immune response between men and women,” Allder suggested.
“Women generally have stronger immune reactions to vaccines, which might lead to a greater protective effect. Additionally, shingles is more common in women, so reducing its occurrence in this group might have a more pronounced impact on dementia rates,” he explained.
In the United States,
Medicare or insurance may cover all or part of it. Generally in the U.S., the vaccine costs around $400 for the 2-dose course. According to the CDC, the vaccine is not associated with any severe adverse events, and is over 90% effective in preventing shingles.
In the United Kingdom, the shingles vaccine is provided free by the National Health Service (NHS) to people between the ages of 60 and 80 and those who are
The researchers who conducted the current study suggest that if further research verifies their findings, the shingles vaccine could be a much more cost-effective way to prevent or delay the condition than existing pharmaceutical interventions.
Nevertheless, some key questions remain in place.
The current study assessed dementia risk in people who had received the older vaccine, which used a live-attenuated form of the virus. Shingrix is a recombinant zoster vaccine.
David Cutler, MD, board-certified family medicine physician at Providence Saint John’s Health Center in Santa Monica, CA, not involved in the research, urged some caution about the findings.
Cutler asked: “If the effect on dementia was real, was it due to the vaccine or was it due to the lower incidence of shingles in the study population?“
“Clearly the Zostavax vaccine was effective at preventing shingles. However,“ he cautioned, “that vaccine is no longer available in the United States. Instead, we have the much more effective Shingrix vaccine.”
“Until a study is done comparing the Zostavax and Shingrix vaccines, involving thousands of people over many years (very costly, and unlikely to occur) it won’t be known if the Shingrix vaccine will yield comparable effects,” he told MNT.
According to Allder:
“While this study provides strong evidence of a link between shingles vaccination and lower dementia risk, a randomized controlled trial would be needed to establish a definitive causal relationship. If confirmed, this could shift public Health priorities and encourage further research into how vaccines might play a role in preventing neurodegenerative diseases.”
Cutler agreed. “For now, a good take home point is that shingles vaccines are effective for preventing shingles, which is adequate reason for getting this vaccine if you are eligible. An additional, benefit might be protection against dementia,” he told us.
However, he added that: “This protection is far from assured. So […] the other known means of preventing cognitive decline as we age should still be pursued.”
