Getting vaccinated against shingles could help keep dementia at bay.
- 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 dementia increasedTrusted Source by
117% between 1990 and 2016, with more than 57 million people now affected by
the condition. And numbers are projected to rise to more than 150 million by
2050.
The Centers for Disease
Control and Prevention (CDC) adviseTrusted Source that people
can help reduce their risk of developing dementia by maintaining an active
lifestyle and healthy diet, and controlling conditions, such as diabetes and high blood pressure.
However, some risk factors, including age and genetics, are beyond a person’s
control.
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 NatureTrusted Source, has demonstrated
that vaccination against shingles, which occurs when the varicella zoster virusTrusted Source reactivates
some time after initial infection, could decrease dementia risk by as much as
20%.
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.”
Strongest
evidence yet on dementia and shingles
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.
Shingles
vaccine reduced dementia risk by 20%
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.”
Women see
the greatest dementia risk reduction
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 postherpetic neuralgiaTrusted Source — chronic
nerve pain that can last up to several months after shingles — in both men and
women.
“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.
Shingles
vaccine: A cost-effective way to prevent or delay dementia?
In the United
States, the CDCTrusted Source recommend
the shingles vaccination, Shingrix,
for those aged 50 or over, and for anyone over the age of 19 with a weakened
immune system.
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 immunocompromisedTrusted Source. Each
dose of the 2-dose course costs the NHS £160. It is also available privately, costing
around £460 for two doses.
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.
Do current
shingles vaccines yield the same protective effect?
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.”
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