Scientists close in on cause of Alzheimer’s as they set sights on a common virus

Groundbreaking research shows that a virus that infects a million Americans every year could increase the risk of dementia.

Researchers at Stanford found that shingles, a virus that causes painful skin rashes, could increase the risk of developing Alzheimer’s disease. people who received a vaccine for it were 20 percent less likely to develop the condition years later.

This emerging area of ​​research, which links viruses that cause chickenpox, herpes and shingles to dementia, could be the key to breakthroughs in the Alzheimer’s mystery, experts say.

Researchers have only recently begun to investigate the link between viruses, such as varciella-zoster, which causes shingles, and neurodegenerative diseases. They are also investigating the virus that causes herpes, which is in the same family as varciella-zoster

Shingles is caused by the same virus that causes chickenpox. After you contract chickenpox, the virus called varicella-zoster hides in your nervous system for life.

As a person ages, the virus can randomly reactivate and travel through the nervous system to the skin according to Mayo Clinic. Doctors aren’t sure what reactivates the virus, but it often occurs in people as they age or become ill, suggesting it may be related to a weakened immune system.

About a million people in the US get shingles every year, According to the CDC.

At the same time, 500,000 Americans are diagnosed with Alzheimer’s every year. Despite how common the disease is, research into the cause of the disease has made little progress in recent decades.

Dr. Geldsetzer’s study, which represents a new theory for studying the disease, has yet to be reviewed by other scientists.

Yet it has been made available online through the National Institute of Health since May 2023, and widely endorsed by other scientists in public.

The study looked at 300,000 health records of people born in Wales between 1925 and 1942 and followed them over time – looking for their shingles vaccination, shingles diagnosis and dementia diagnosis.

In Wales they have set guidelines for shingle vaccination with an age limit, based on data showing the vaccination was not effective in people over 80 years of age.

So the researchers had to study two groups: those born before 1933 who were not vaccinated and those born after 1933 who were.

The groups were otherwise comparable in terms of age, pre-existing conditions and other health history.

They found that vaccination reduced the risk of developing dementia by 20 percent in the seven years after getting the shot.

‘We are looking at a causal effect. And it is specific to dementia. There’s clearly something going on here.’ Pascal Geldsetzer, epidemiologist at Stanford University told STAT.

To ensure that what they saw was not specific to Wales alone, Dr. Geldsetzer and his team then conducted similar analyzes in the United Kingdom and Australia, and discovered the same trend.

At the same time, researchers at the University of Oxford conducted studies that contributed to the theory linking shingles to Alzheimer’s disease.

A 2024 study published in the journal Nature looked at the health records of 200,000 Americans and saw how they fared after receiving a 2017 approved form of shingles vaccine called Shingrix.

A 2024 study showed that the vaccine Shingrix was linked to a “significantly” lower risk of dementia compared to Zostavax and shots for other diseases. This adds weight to other emerging research suggesting a link between shingles and dementia

The vaccine reduced the risk of dementia by 17 percent for six years after it was given, compared to older shingles vaccines that were less effective.

Paul Harrison, the lead author and professor of psychiatry at the University of Oxford, told STAT: ‘I have always been a proponent of vaccines, but the Covid vaccine reinforced for me that there may be long-term benefits to vaccination that go beyond only stopping in the short term. effects.’

Because the link between shingles and dementia is still so new, research has yet to explain how shingles can cause some cases of the disease.

They think it may be related to the period of time the virus hides in your nervous system after you contract chickenpox.

Although it appears that 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.

As you get older or become ill, or if the immune system is otherwise busy, this gives the virus the opportunity to spread to other parts of the body.

This includes the blood vessels, which neurologists from the University of Alabama has found that this can cause disruption of blood flow in the brain.

Reducing or interrupting blood flow to the brain for an extended period of time can put stress on the brain’s delicate cells, causing damage or death that can accumulate over time, which can contribute to a greater risk of dementia.

Whatever the cause of virus-induced dementia, 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.

Studying the link between neurodegeneration and viruses is therefore a new opportunity, bringing new scientific insights into the puzzle that is Alzheimer’s disease.

Thinking of all the new people who have participated in Alzheimer’s research in recent years, Dr. Nagel told STAT: “I really believe that in the next decade we will see tremendous progress in finding new mechanisms and finding new ways to try to slow things down.”