Common stomach bug carried by 1 in 4 people ‘could travel to the brain and trigger Alzheimer’s’

For most, the common stomach bug won't cause any health problems.

But about 15 per cent of people will get ulcers in the lining of their stomach or duodenum, the start of the small intestine.

Others might develop indigestion, gastritis or even stomach cancer.

Now, scientists say H. pylori could affect more than just the gut.

A team of McGill University researchers analysed the health data of over four million people aged 50 and above between 1988 and 2019.

The study - published in the journal - found that people who experienced symptoms from an H. pylori infection were 11 per cent more likely to develop Alzheimer's disease, the most common form of dementia.

The risk of developing the brain robbing disease was highest between seven and 10 years after the onset of the infection, with sufferers 24 per cent more likely to have Alzheimer's.

Scientists said they couldn't prove that an H. pylori infection is definitely the cause of an increased risk of Alzheimer's.

But they speculated that the bug might travel to the brain, leading to inflammation and loss of brain cells.

"A link between H. pyloris and the central nervous system has been proposed," the .

"H. pyloris can access the brain via the oral-nasal-olfactory axis or by infected circulating monocytes through a disrupted blood-brain-barrier, potentially leading to neuroinflammation, neuronal damage, and neurodegeneration."

The bacteria might also disrupt the gut microbiome, researchers suggested, leading to the overproduction of amyloid – the sticky protein that's present in the brains of Alzheimer’s patients.

Finally, the McGill team suggested that damage to the gut caused by a chronic H. pyloris infection "could affect the absorption of vitamin B12 and iron, a deficit of which is associated with dementia".

"The study opens avenues for future research, particularly exploring whether eradicating this bacterium could effectively prevent Alzheimer's disease in some people," stated.

The research team estimated that eradicating the bug could prevent about 200,000 cases of Alzheiemer’s globally each year.

Dr Paul Brassard, the study’s senior author and a Professor in McGill’s Department of Medicine, said: “We hope the findings from this investigation will provide insight on the potential role of H. pylori in dementia in order to inform the development of prevention strategies, such as individualized eradication programs, to reduce infections at the population level."

 “Given the global ageing population, dementia numbers are expected to triple in the next 40 years. However, there remains a lack of effective treatment options for this disease."

There are currently around 900,000 people with dementia in the UK, with number to rise to 1.6 million people by 2040, according to .