A preliminary study reveals that people with dementia have a different composition of the bacteria in their gut, raising questions about whether "insects" play a role in brain disease.

Japanese researchers have found that, compared to older adults without dementia, sufferers typically had a very different "microbiome". The term refers to the billions of bacteria and other microbes present in the digestive system.

As recent studies have revealed, these intestinal insects do more than facilitate digestion. They seem to affect a range of bodily functions, from immune defenses to vitamin production, to anti-inflammatory compounds and even chemicals relaying messages between brain cells.

The researchers also discovered that the composition of the intestinal microbiome was linked to risks for various conditions, such as obesity, asthma, and type 1 diabetes.

These studies, however, do not prove that intestinal bacteria contribute directly to these diseases, or protect them directly against them. And the new study either, emphasized the experts.

The study only revealed that a group of dementia patients had different intestinal microbes from dementia-free adults, said Mary Sano, director of the Alzheimer's Disease Research Center. at Mount Sinai in New York.

"You would expect to see a lot of differences between these two groups of people," said Sano, who did not participate in the study.

And it is very possible, she said, that dementia is the cause of intestinal differences, not the result. For example, diet plays a crucial role in the composition of intestinal bacteria and people with dementia often have changes in their appetite and end up suffering from malnutrition.

Keith Fargo is Director of Scientific Programs and Outreach for the Alzheimer's Association. He made the same remark.

"At this point, we do not know that this association is causal," said Fargo, who did not participate in the study. "We do not know what happened first – dementia or differences in the intestinal microbiome."

The results should be presented at a conference of the American Stroke Association in Honolulu next week. Research published in meetings should be considered preliminary until published in a peer-reviewed journal.

For the study, Dr. Naoki Saji and colleagues at the National Geriatrics and Gerontology Center in Obu, Aichi, Japan, analyzed stool samples from 128 older adults, with or without dementia.

In general, the researchers found that patients with dementia had higher concentrations of some compounds – including ammonia, indole, and phenol – but lower levels of Bacteroides.

Bacteroids are a group of bacteria that can be beneficial to the intestines because they eliminate the "bad" bacteria that cause the infection.

For now, said Fargo, the relationship between the gut microbiome and the disease is an interesting and "booming" area of ​​research. But it is unclear whether microbes have a direct effect on the risk of dementia.

Other recent studies have examined whether chronic infection was related to dementia. Last week again, researchers announced they have discovered the bacterium that causes gum disease in the brains of people with Alzheimer's disease.

In tests on mice, they showed that bacteria could move from the mouth to the brain, where they attacked nerve cells.

Still other research has revealed particularly high rates of some strains of the herpes virus in the brains of people with Alzheimer's disease.

All this suggests that "external agencies" could play a role in dementia, according to Fargo. But, he said, nobody knows what's going on yet.

Sano accepted. She said that while the presence of some infectious bedbugs has been linked to dementia, it may not be the infections themselves that matter. The bacteria of gum disease and herpes viruses are extremely common, Sano said. So transporting these insects alone is not the critical factor.

Instead, Sano speculated, there might be something in the body's general response to "an insult or injury" that is the real problem.

Fargo recommended that people focus on lifestyle-related factors that are closely related to improving brain health: exercise regularly, do not smoke, and adopt a healthy diet. the heart.

He also stressed the importance of reducing blood pressure. An important trial published this week found that "intensive" blood pressure control – less than 120 mm Hg – reduced the risk of developing lighter memory and thinking problems in the elderly.