Scientists close in on cause of Alzheimer’s as they set sights on a common virus
Cutting-edge research suggests that a virus, which infects a million Americans each year, could raise your risk of dementia.
Stanford researchers found that shingles, a virus that causes a painful rash, could be increase your risk of developing Alzheimer’s, as people who received a vaccine for it were 20 percent less likely develop the disorder years later.
This emerging field of research, linking viruses that cause chickenpox, herpes and shingles to dementia, could be the key to making breakthroughs in the Alzheimer’s mystery, experts say.
Shingles is a viral infection that is caused by the same virus responsible for chickenpox. Sufferers get rashes of blisters that are painful and can be itchy
Researchers have only recently begun investigating the link between viruses, like varciella-zoster, which causes Shingles, and neurodegenerative disease. They are also examining the virus that causes herpes, which is in the same family as varciella-zoster
Shingles is caused by the same virus that causes chicken pox. After catching chicken pox, the virus, called varicella-zoster, hides out in your nervous system for life.
At random, as someone ages, the virus can reactivate, travelling along the nervous system to the skin according to Mayo Clinic. Doctors are unsure what causes the virus to reactivate, but it tends to happen in people as they age or get sick, which suggests that it could have do with a weakened immune system.
About one million people in the US get shingles each year, according to the CDC.
At the same time, 500,000 Americans are diagnosed with Alzheimer’s each year. Despite how common the disease is, research into the cause of the disease has made little progress over the past decades.
Dr Geldsetzer’s study, which represents a new theory for studying the disease, has yet to be peer reviewed by other scientists.
Still it has been made available online through the National Institute of Health since May 2023, and widely approved by other scientists in public.
The study looked at 300,000 health records of people born in Wales from 1925 to 1942 and tracked them over time – looking for their shingles vaccination, shingles diagnosis and dementia diagnosis.
In Wales, they designed shingle vaccination guidelines to have an age cutoff – based on data that showed the vaccination wasn’t effective in people over 80.
So the researchers had two groups to study – those born before 1933 who didn’t get vaccinated and those born after 1933 who did.
The groups were otherwise similar in age, pre-existing conditions and other health history.
They found that vaccination reduced risk of developing dementia by 20 percent in the seven years after getting the shot.
‘We’re looking at a causal effect. And it’s specific to dementia. There is something clearly going on here.’ Pascal Geldsetzer, Stanford University epidemiologist told STAT.
To make sure what they were seeing wasn’t specific to Wales alone, Dr Geldsetzer and his team then performed similar analysis in the United Kingdom and Australia, and found the same trend.
At the same time, researchers at Oxford University were performing studies that added to the theory linking shingles to Alzheimer’s.
A 2024 study published in the journal Nature looked at the health records of 200,000 Americans, seeing how they fared after receiving a form of shingles vaccine approved in 2017 called Shingrix.
A 2024 study showed the vaccine Shingrix was linked to a ‘significantly’ lower risk of dementia compared to Zostavax and jabs for other illnesses. This adds weight to other emerging research suggesting a link between shingles and dementia
The vaccine reduced risk of dementia by 17 percent for six years after it was delivered when compared to older shingles vaccines that were less effective.
Paul Harrison, the lead author and a professor of psychiatry at Oxford University told STAT: ‘I’ve always been a vaccine believer, but the Covid vaccine reinforced to me that there may be long-term benefits to vaccination beyond simply stopping short-term effects.’
Since the link between shingles and dementia is still so new, research has yet to explain how shingles may be causing some cases of the disease.
They think it may have to do with the period of time when the virus hides out in your nervous system after catching chicken pox.
Though it seems like the virus is harmless, research from the Netherlands suggests that your immune system is actively working to keep it in check while it camps out in the body.
When you age or get sick or the immune system is otherwise busy, this gives an opportunity for the virus to strike out in other parts of the body.
This includes the blood vessels, which neurologists from the University of Alabama has found can cause disruption to the blood flow of the brain.
Reducing or interrupting blood flow to the brain over a prolonged period of time can put the delicate cells of the brain under stress – causing damage or death that could add up over time, contributing to greater risk for dementia.
Whatever the cause of a virus-driven dementia might be, scientists like Dr Maria Nagel, a University of Colorado neurovirologist who studies shingles, are excited that researchers are looking into it.
For a long time, the majority of Alzheimer’s research and funding focused on just one theory.
So studying the link between neurodegeneration and viruses is a new opportunity, bringing new scientific minds to the puzzle that is Alzheimer’s.
Thinking about all the new people who have joined in Alzheimer’s research in recent years, Dr Nagel told STAT: ‘I really do believe that in the next 10 years or so we’re going to see huge strides in finding new mechanisms and finding new ways to try to slow things down.’
