This could be a big deal. There are very few, if any, treatments that can prevent or slow down dementia, beyond good lifestyle habits like getting enough sleep and exercise. The possibility that a known, inexpensive vaccine could offer real protection is enormously meaningful. We have good reason to be confident in the findings: While this study is perhaps the most prominent to show the protective effects of the shingles vaccine, other studies of the vaccine have come to similar conclusions.
Beyond the promise of preventive treatment, the new study adds further evidence to a growing body of research raising the possibility that we have been thinking about neurodegenerative diseases like dementia and Alzheimer’s all wrong. It’s possible these horrible conditions are caused by a virus — and if that’s the case, eliminating the virus could be enough to prevent or treat the diseases.
How the study worked
To understand why the new shingles vaccine study is such a big deal, it helps to know a little bit about how medical studies are carried out. (...)
The new study... took advantage of a quirk in Welsh health policy to do something better. Beginning on September 1, 2013, anyone in Wales who was 79 became eligible to receive a free shingles vaccine. (Those who were younger than 79 would become eligible once they turned that age.) But anyone who was 80 or older was not eligible on the grounds that the vaccine is less effective for the very old.
The result was what is known as a “natural experiment.” In effect, Wales had created two groups that were essentially the same — save for the fact that one group received the shingles vaccine and one group did not.
The researchers looked at the health records of the more than 280,000 adults who were 71 to 88 years old at the start of the vaccination program and did not have dementia. They focused on a group that was just on the dividing line: those who turned 80 just before September 1, 2013, and thus were eligible for the vaccine, and those born just after that date, who weren’t. Then, they simply looked at what happened to them.
By 2020, seven years after the vaccination program began, about one in eight older adults, who by that time were 86 and 87, had developed dementia. But the group that had received the shingles vaccine were 20 percent less likely to be diagnosed with the disease. Because the researchers could find no other confounding factors that might explain the difference — like years of education or other vaccines or health conditions like diabetes — they were confident the shingles vaccine was the difference maker.
A new paradigm in dementia research?
As Paul Harrison, a professor of psychiatry at the University of Oxford who was not involved in the study, told the New York Times, the research indicates that the shingles vaccine appears to have “some of the strongest potential protective effects against dementia that we know of that are potentially usable in practice.”
But this is a vaccine originally designed to prevent shingles. Why does it also appear to help with dementia?
Scientists theorize it could be related to inflammation. Shingles, or herpes zoster, is caused by the same virus responsible for chickenpox, which lies dormant in nerve cells after an initial infection and can reawaken decades later, causing painful rashes.
That reactivation creates intense inflammation around nerve cells, and chronic inflammation is increasingly recognized as a major factor in cognitive deterioration. By preventing shingles, the vaccine could indirectly protect against the neural inflammation associated with dementia.
What about the amyloid and tau protein plaques that tend to be found in the brains of people suffering from Alzheimer’s, which have long been thought of as the primary cause of the disease? It’s possible that these may actually be the body’s response to an underlying infection. That could help explain why treatments that directly target those plaques have been largely ineffective — because they weren’t targeting the real causes.
Beyond the promise of preventive treatment, the new study adds further evidence to a growing body of research raising the possibility that we have been thinking about neurodegenerative diseases like dementia and Alzheimer’s all wrong. It’s possible these horrible conditions are caused by a virus — and if that’s the case, eliminating the virus could be enough to prevent or treat the diseases.
How the study worked
To understand why the new shingles vaccine study is such a big deal, it helps to know a little bit about how medical studies are carried out. (...)
The new study... took advantage of a quirk in Welsh health policy to do something better. Beginning on September 1, 2013, anyone in Wales who was 79 became eligible to receive a free shingles vaccine. (Those who were younger than 79 would become eligible once they turned that age.) But anyone who was 80 or older was not eligible on the grounds that the vaccine is less effective for the very old.
The result was what is known as a “natural experiment.” In effect, Wales had created two groups that were essentially the same — save for the fact that one group received the shingles vaccine and one group did not.
The researchers looked at the health records of the more than 280,000 adults who were 71 to 88 years old at the start of the vaccination program and did not have dementia. They focused on a group that was just on the dividing line: those who turned 80 just before September 1, 2013, and thus were eligible for the vaccine, and those born just after that date, who weren’t. Then, they simply looked at what happened to them.
By 2020, seven years after the vaccination program began, about one in eight older adults, who by that time were 86 and 87, had developed dementia. But the group that had received the shingles vaccine were 20 percent less likely to be diagnosed with the disease. Because the researchers could find no other confounding factors that might explain the difference — like years of education or other vaccines or health conditions like diabetes — they were confident the shingles vaccine was the difference maker.
A new paradigm in dementia research?
As Paul Harrison, a professor of psychiatry at the University of Oxford who was not involved in the study, told the New York Times, the research indicates that the shingles vaccine appears to have “some of the strongest potential protective effects against dementia that we know of that are potentially usable in practice.”
But this is a vaccine originally designed to prevent shingles. Why does it also appear to help with dementia?
Scientists theorize it could be related to inflammation. Shingles, or herpes zoster, is caused by the same virus responsible for chickenpox, which lies dormant in nerve cells after an initial infection and can reawaken decades later, causing painful rashes.
That reactivation creates intense inflammation around nerve cells, and chronic inflammation is increasingly recognized as a major factor in cognitive deterioration. By preventing shingles, the vaccine could indirectly protect against the neural inflammation associated with dementia.
What about the amyloid and tau protein plaques that tend to be found in the brains of people suffering from Alzheimer’s, which have long been thought of as the primary cause of the disease? It’s possible that these may actually be the body’s response to an underlying infection. That could help explain why treatments that directly target those plaques have been largely ineffective — because they weren’t targeting the real causes.
by Bryan Walsh, Vox | Read more:
Image: H. Rick Bamman/ZUMA Wire/Alamy Live News
[ed. See also: Shingles Vaccine Can Decrease Risk of Dementia, Study Finds (NYT):]
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“If you’re reducing the risk of dementia by 20 percent, that’s quite important in a public health context, given that we don’t really have much else at the moment that slows down the onset of dementia,” said Dr. Paul Harrison, a professor of psychiatry at Oxford. (...)Several previous studies have suggested that shingles vaccinations might reduce dementia risk, but most could not exclude the possibility that people who get vaccinated might have other dementia-protective characteristics, like healthier lifestyles, better diets or more years of education.
The new study ruled out many of those factors. (...)
They also examined medical records for possible differences between the vaccinated and unvaccinated. They evaluated whether unvaccinated people received more diagnoses of dementia simply because they visited doctors more frequently, and whether they took more medications that could increase dementia risk.
“They do a pretty good job at that,” said Dr. Jena, who wrote a commentary about the study for Nature. “They look at almost 200 medications that have been shown to be at least associated with elevated Alzheimer’s risk.”
He said, “They go through a lot of effort to figure out whether or not there might be other things that are timed with that age cutoff, any other medical policy changes, and that doesn’t seem to be it.”
The study involved an older form of shingles vaccine, Zostavax, which contains a modified version of the live virus. It has since been discontinued in the United States and some other countries because its protection against shingles wanes over time. The new vaccine, Shingrix, which contains an inactivated portion of the virus, is more effective and lasting, research shows.
A study last year by Dr. Harrison and colleagues suggested that Shingrix may be more protective against dementia than the older vaccine. Based on another “natural experiment,” the 2017 shift in the United States from Zostavax to Shingrix, it found that over six years, people who had received the new vaccine had fewer dementia diagnoses than those who got the old one. Of the people diagnosed with dementia, those who received the new vaccine had nearly six months more time before developing the condition than people who received the old vaccine.
The new study ruled out many of those factors. (...)
They also examined medical records for possible differences between the vaccinated and unvaccinated. They evaluated whether unvaccinated people received more diagnoses of dementia simply because they visited doctors more frequently, and whether they took more medications that could increase dementia risk.
“They do a pretty good job at that,” said Dr. Jena, who wrote a commentary about the study for Nature. “They look at almost 200 medications that have been shown to be at least associated with elevated Alzheimer’s risk.”
He said, “They go through a lot of effort to figure out whether or not there might be other things that are timed with that age cutoff, any other medical policy changes, and that doesn’t seem to be it.”
The study involved an older form of shingles vaccine, Zostavax, which contains a modified version of the live virus. It has since been discontinued in the United States and some other countries because its protection against shingles wanes over time. The new vaccine, Shingrix, which contains an inactivated portion of the virus, is more effective and lasting, research shows.
A study last year by Dr. Harrison and colleagues suggested that Shingrix may be more protective against dementia than the older vaccine. Based on another “natural experiment,” the 2017 shift in the United States from Zostavax to Shingrix, it found that over six years, people who had received the new vaccine had fewer dementia diagnoses than those who got the old one. Of the people diagnosed with dementia, those who received the new vaccine had nearly six months more time before developing the condition than people who received the old vaccine.
