Gastric conditions, such as ulcers and stomach cancer, which are caused by the bacteria Helicobacter pyloriincrease the risk of developing Alzheimer’s disease, according to an observational study carried out by a team from McGill University and published in recent days in Alzheimer’s & Dementia, The Journal of the Alzheimer’s Association.
Researchers at McGill University have been interested in the “infectious hypothesis” for several years. According to this, infections that a person has had during their life could contribute to the development of Alzheimer’s disease. They trigger an inflammatory process which promotes the deposition of amyloid plaques in the brain, characteristic of this neurodegenerative disease. In a previous study, these researchers were able to confirm the existence of an association between “the burden of previous infections and the development of Alzheimer’s disease”. But among the various infectious diseases they examined, gastritis, an infection of the stomach lining, appeared “more strongly associated with Alzheimer’s disease” than the others.
Gastritis being caused by bacteria Helicobacter pylori (H. pylori), these scientists then decided to study in more detail this possible link between H.pylori and Alzheimer’s in a population of more than four million individuals aged 50 and over. Analysis of health data collected between 1988 and 2017 from this population in the United Kingdom revealed that a symptomatic infection induced by this bacteria increases the risk of developing Alzheimer’s disease by an average of 11% in people with crossed fifty. “This is an increase which is modest, but which is statistically significant, because we detected it in a large population”, affirms the one who led the study, the Dr Paul Brassard, specialist in public health and preventive medicine at the McGill University Health Center (MUHC).
The researchers also noted a variation in this risk over time. In fact, the risk increases until reaching a maximum of 24%, ten years after the clinical manifestation of infection by H. pylori. Then it decreases. “This may mean that a decade is the time needed to induce an inflammatory process [notamment neuro-inflammatoire néfaste] or erosion of the gastric mucosa which would notably compromise the absorption of vitamin 12, a deficiency of which is associated with dementia,” says the Dr Armband.
However, it is not enough to be infected by the bacteria to see your risk of Alzheimer’s increase, underlines the Dr Armband. This must cause clinical symptoms, such as indigestion, heartburn, ulcers or gastric cancer. However, only around 20% of people who carry the bacteria will ultimately develop clinically detectable signs.
We can catch H. pylori by consuming contaminated water or food. The bacteria can also be spread from person to person through saliva. In Canada, it is estimated that 20 to 30% of the population carriesH. pylori. The prevalence of the bacteria is, however, higher among older people with weaker immune systems, among immigrants from emerging countries, as well as among indigenous communities who often live with several people under the same roof, which favors transmission. intrafamily of the bacteria.
In certain countries, such as China, Japan and Korea, where the frequency of stomach cancer is particularly high, a population program to eradicate the bacteria is being tested. H. pylori. We carry out screening campaigns for the bacteria, and when a person is infected, we administer a cocktail of antibiotics for 14 days which generally eliminates the bacteria and thus prevents the development of gastric cancer.
The cost-benefit ratio of such a program has been shown to be advantageous in those countries where stomach cancer is quite common. If the benefit proves interesting for gastrointestinal problems, in turn, it could also benefit the population in the prevention of Alzheimer’s disease, notes Dr Armband.
“As we still do not have treatments [efficaces] for Alzheimer’s disease, we focus on risk factors [qui sont modifiables] and on the means to prevent it,” he concludes.