It has long been suspected that the shingles vaccine has an impact on the development of dementia. However, there was no convincing evidence from clinical trials to support the suspected protective effect of the vaccine against neurodegenerative disease.
Now researchers from Stanford Medical University report Nature And Cell that people who received the shingles vaccine were about 20 percent less likely to develop dementia than those who did not. The analysis, based on Welsh health data, also found that vaccinated people diagnosed with dementia were less likely to die from the disease, suggesting that vaccination may influence disease progression as well as risk.
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Why Shingles May Matter in Dementia
The varicella zoster virus, which causes chickenpox in children, remains dormant in the nervous system long after the initial infection has resolved. In old age, the virus can reactivate as shingles, which can sometimes lead to severe neurological complications.
In recent years, researchers have increasingly explored the possibility that viruses that infect the nervous system may contribute to the risk of dementia. Millions of people around the world live with dementiaIdentifying modifiable risk factors has become a public health priority.
According to the study press releaseprevious studies have reported an association between herpes zoster vaccination and lower rates of dementia. However, these conclusions were accompanied by great uncertainty:
“All of these association studies suffer from a basic problem: people who get vaccinated have different health behavior “The study's senior author, Pascal Geldsetzer, an assistant professor of primary care and population health at Stanford University, said in a press release. “Overall, the evidence is not considered strong enough to make any recommendations.”
Unusual vaccination program provides robust evidence on dementia
A quirk in public health policy allowed the Stanford team to overcome this limitation.
In 2013, Wales faced a shortage of tiles. vaccine and limited eligibility to people who turned 79 on September 1 of that year to only one year. Those who were already 80 years old were excluded forever.
As a result, eligibility depended entirely on a narrow date of birth cutoff rather than on health status or personal choice, and the researchers were able to isolate the effect of vaccination itself.
“Due to the unique way the vaccine was administered, there is much less potential for bias in the analysis than usual,” Geldsetzer said.
The study analyzed the records of more than 280,000 adults aged 71 to 88 who did not initially have dementia. Over seven years, vaccinated people saw a 37 percent reduction in the incidence of shingles and a 20 percent reduction in the risk of dementia.
“What makes the study so powerful is that it is essentially like a randomized trial with a control group—those too old to be eligible for the vaccine—and an intervention group—those young enough to be eligible for the vaccine,” he added. “This was a really striking finding. This powerful protective signal was present no matter how you looked at the data.”
Potential of herpes zoster vaccine to slow progression of dementia
Additional analyzes showed benefits beyond delayed onset. Vaccinated individuals were less likely to be diagnosed with mild cognitive impairment, and those vaccinated after a diagnosis of dementia were significantly less likely to be diagnosed with mild cognitive impairment. die of illness over a nine-year follow-up period.
“The exciting thing is that this really means that the shingles vaccine not only has preventative, delaying benefits against dementia, but also therapeutic potential for those who already have dementia,” Geldsetzer said.
The biological mechanism remains unknown, although immune system effects or decreased viral reactivation may be possible explanations. Geldsetzer and colleagues are now calling for a large randomized clinical trial to determine whether this association is causal.
This article does not contain medical advice and should be used for informational purposes only.
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