Does shingles vaccination reduce dementia risk? Large study suggests link

Vaccination against shingles may also prevent Dementia caused by Alzheimer’s disease, etc., according to a survey of the health records of nearly 300,000 people in Wales. The analysis found that vaccination reduced the risk of dementia by 20%. However, some puzzling aspects of the analysis have raised debate about the robustness of the study.

This study was published on the medRxiv preprint server on May 25, but has not yet been peer-reviewed.

“If that’s true, it’s a big deal,” said epidemiologist Alberto Asherio of Harvard University in Cambridge, Massachusetts, who was not involved in the study. “Even a small reduction in risk can make a big difference.”

Relationship between dementia and infectious diseases

The idea that viral infections may play a role in at least some cases of dementia Its origins date back to the 1990s, when University of Manchester biophysicist Ruth Izaki and her colleagues discovered the herpes virus in the brains of people who died of dementia.². This theory is controversial among Alzheimer’s researchers. However, recent research suggests that people infected with viruses that affect the brain have a higher incidence of neurodegenerative diseases.³. Studies also suggest that people vaccinated against certain viral diseases are less likely to develop dementia.^Four.

Do infectious diseases cause some cases of Alzheimer’s disease?

However, all these epidemiological studies share an important problem. People who get any type of vaccine tend to have healthier lifestyles than those who don’t.^FiveThis means that other factors may be responsible for the reduced risk of diseases such as Alzheimer’s disease.

With that in mind, epidemiologist Pascal Gerdsetzer and colleagues at Stanford University in California turned to a natural experiment, a shingles vaccination program in Wales, which began on September 1, 2013. rice field. Shingles is caused by reawakening of the inactive varicella-zoster virus (VZV). , herpes virus It causes chickenpox, which affects most people. Shingles is most common in older people and can cause severe pain and a rash.

natural experiment

Data suggest vaccine is more effective for people under 80. As a result, only those who were under 80 at the start of the programme, i.e. born after 2 September 1933, were eligible to take the jab in Wales. Those born before September 2, 1933 were not eligible for life.

Researchers examined the electronic health records of 296,603 people born between 1925 and 1942 and found that about half of the subjects died within seven years of the availability of the vaccine known as Zostavax. It turned out that he had been vaccinated. The researchers also found that people in the eligible group were 8.5% less likely to develop dementia compared to the unfit group. Considering that only about half of the participants received the vaccine, the researchers calculated that the vaccine reduced dementia risk by 19.9% ​​overall.

Overcoming Alzheimer’s disease: looking to future cures

The birthday deadline made it possible to compare people born within a few weeks. Gerdsetzer says there is no plausible reason why people who turn 80 in August are more likely to develop dementia than those who have birthdays in September. The only difference, he said, is whether people with late birthdays can get the shingles vaccine. Other factors that could influence dementia incidence, such as public testing campaigns, would have affected both groups equally.

“I think it’s a very strong paper,” says Asherio. Although the difference in dementia rates could have arisen by chance, the authors say they had adequate testing to rule out other explanations.

Dr. Itzaki is thrilled that the study, among other things, supports the theory that viruses are the triggers for Alzheimer’s disease. “This is absolutely in line with what we’ve been saying since 1991, which is very encouraging,” she said, adding that the new study could explain the reduced risk of dementia in the vaccinated group. He added that it is unique in that it eliminates the factor of

Mysterious Discovery

Some still urge caution. “It’s a good study, but it’s far from conclusive,” says Maria Grimoire, an epidemiologist at the University of California, San Francisco, who studies Alzheimer’s disease. She notes that most of the difference in dementia rates was recorded in the first four years after vaccination, whereas Alzheimer’s disease develops over decades. Gerdsetzer said the vaccine could just delay the onset of dementia, adding that he would like to redo the analysis in the future to see if the effect persists beyond seven years.

The authors also found that the effects were predominantly in women. There was no statistically significant difference in the incidence of dementia between included and non-targeted men. Gerdsetzer isn’t sure why, but points out that women and men seem to have different rates of shingles and dementia.

But critics have focused on this contradiction and questioned whether the results prove a causal link between vaccines and dementia. Cornelia Van Dyne, an epidemiologist at the University of Oxford in England, said the study was “fantastic” but that the fact that men were unaffected casts doubt on the study. “I’m not convinced that chance or bias should be ruled out,” she says.

mystery of how it works

It’s also unclear why and how vaccines can prevent dementia, and whether a new vaccine called Xingrix, which replaces Xostavax, would have the same effect. Some have pointed out that Zostavax was a fairly ineffective vaccine. Clinical trials have found it reduces the risk of shingles by about 50%. Geldsetzer said the vaccine could trigger an immune response that could help reduce the risk of dementia.

Grimoire added that another group needs to be studied to replicate the results before the results influence policy. She and others agree that a clinical trial, not a review of health records, is the best way to confirm results. Several trials are underway to test new shingles vaccines, and Gerdsetzer said it may be possible to study participants’ cognitive function.

“This is a really important step forward, so it’s good for all of us,” Asherio said. “I hope that’s true.”

Nature recognizes that both sex and gender exist on a spectrum and do not always coincide. The use of the words “female” and “male” here reflects the language of the research described in the article.