Stomach bacteria and dementia: is there a link?

Researchers at the German Charité Clinic and McGill University in Canada have found a link between infection with the stomach bacterium Helicobacter pylori and Alzheimer's disease. The infection can increase the risk of developing dementia in people over 50 by 11%, and ten years after infection - by 24% or more.

In the new study, researchers analyzed data from about 4 million patients over 30 years. Since there is still no effective drug for dementia, researchers are trying to identify the main risk factors for the disease.

Helicobacter pylori can penetrate the central nervous system.

According to experts, due to the current processes of population aging on Earth, humanity may face an even greater spread of dementia in the next 40 years. Despite new developments, Alzheimer's therapy can only temporarily support patients. This is one of the most important reasons why scientists are trying to determine the exact causes of dementia.

Researchers have long suspected that the most common intestinal microbe Helicobacter pylori may influence the development of dementia. It is known that almost a third of the world's population is infected with this bacterium. It can be asymptomatic, but Helicobacter pylori can lead to inflammation of the stomach lining and cause stomach cancer.

Numerous scientific studies have confirmed the link between H. pylori and the central nervous system. Researchers have also found that when the stomach is infected with these microbes, it has poor absorption of vitamin B12 and iron, which also increases the risk of dementia.

"We know that the bacterium can reach the brain in different ways, potentially causing inflammation, damage, and destruction of neurons there, "explains the first author of the study, professor, pharmacoepidemiologist at the Charité Clinic, Antonio Douros.

Most studies examining the link between H. pylori infection and Alzheimer's disease had methodological limitations. For example, the number of participants was too small, so it was impossible to say for sure how strong the link between the bacterium and Alzheimer's disease was.

A representative study of more than four million people

German and Canadian scientists have compensated for these limitations in a new study. The large sample size of more than four million people, as well as the time lag between infection and a possible increase in Alzheimer's risk, provided more accurate results, according to experts.

To assess the link between H. pylori and Alzheimer's disease over a person's lifetime, the researchers used data from electronic patient records in the United Kingdom.

"Our study shows that symptomatic H. pylori infections after the age of 50 can increase the risk of Alzheimer's disease by 11%. The peak increase in risk is 24% about ten years after the initial infection," says Douros, summarizing the work of his colleagues.

The expert emphasizes that this does not mean that everyone who has suffered a symptomatic infection will necessarily develop Alzheimer's disease.

Calculations show that patients infected with H. pylori have a 24% higher risk of developing Alzheimer's disease after the age of 50.

Can Alzheimer's be prevented?

Given the new data, researchers believe that dementia can be prevented. "For us, this discovery supports the suggestion that H. pylori infection may be a modifiable risk factor for Alzheimer's disease," said Paul Brassard, MD, PhD, professor of medicine at McGill University.

David S. Knopman, MD, a clinical neurologist specializing in Alzheimer's disease at the Mayo Clinic, was not involved in the study and considers the new data "unhelpful and misleading."

"First, the claim that they are looking at Alzheimer's disease is a gross overstatement of diagnostic specificity. You can be sure that all the cases considered in the study had dementia of various etiologies," says Dr. Nopman.

The neurologist believes that the results of his colleagues' study are not specific and have no biological significance. Nopman believes that the risk of developing dementia is related to general health, and the new report "only adds to the hype and confusion, not to the substance."

Nevertheless, the authors of the study warn that the question of whether eradicating H. pylori can affect the development of Alzheimer's disease remains to be studied and tested in large-scale randomized trials.