Dementia: Your Gut and Brain Have Conversations—and That Could Hold Clues for Treatment and Prevention

The bacteria in our digestive systems could make us prone to developing dementia, a small study has suggested. And experts believe the "conversations" our guts have with our brains could hold clues to developing approaches to prevent and treat the neurodegenerative condition.

In a preliminary study to be presented at the American Stroke Association's International Stroke Conference 2019, Honolulu, scientists showed a link between the gut microbiota and the neurodegenerative disorder whose cause is unknown. The results have not yet been published in a peer-reviewed journal, meaning they should be taken with a pinch of salt.

Researchers in Japan assessed the fecal samples of 128 people: Some had dementia, while the remainder were healthy. The authors did not immediately respond to a request for comment, and it is unclear how many of the participants had the disorder. The team also studied the participants' brains using MRI scanners.

They found patients with dementia had different populations of gut bacteria when compared with those who didn't. This group also had higher levels of chemicals including ammonia. At the same time, the dementia patients had fewer potentially beneficial bacteria called bacteriodes in their feces.

"Gut microbiota is an independent and strong risk factor for dementia," the authors wrote in their presentation.

Dr. Naoki Saji, study author and vice director of the Center for Comprehensive Care and Research on Memory Disorders, National Center for Geriatrics and Gerontology in Japan, commented in a statement: "Although this is an observational study and we assessed a small number of the patients, the odds ratio is certainly high suggesting that gut bacteria may be a target for the prevention of dementia."

Dr. James Pickett, head of research at the Alzheimer's Society charity, told Newsweek: "There's growing evidence that the gut microbes of people with Alzheimer's can change as the disease develops. This study doesn't add anything further to the picture, other than give us more details of which gut bacteria might be involved.

"We already know the gut and brain can communicate, so when something is wrong in the gut it may trigger an emergency response in the brain."

"If we can understand this 'gut-brain conversation' better, it could open up a whole new way to prevent dementia, or develop new treatments," he said.

Dr. Sara Imarisio, head of research at Alzheimer's Research U.K., who was also not involved in the research told Newsweek: "We will need to wait until the researchers publish their full findings before we can tell what further insights we can glean from this study."

She explained that the make-up of gut bacteria is influenced by both genetics and our lifestyle, "so it is one of a number of potential dementia risk factors that we could influence by leading a healthy life."

"To maintain a healthy brain as we age, the best current evidence suggests that we keep physically fit, eat a balanced diet, maintain a healthy weight, not smoke, only drink within the recommended limits and keep blood pressure and cholesterol in check," she said.

As around 50 million people across the world have dementia according to the World Health Organization, and approximately 10 million new cases are diagnosed each year, scientists are working to find not only a treatment but a cause for the condition.

A separate piece of research published in the journal Science Advances offered a different explanation: The bacteria that causes gum disease.

The gingipains enzyme released by the Porphyromonas gingivalis (P. gingivalis) bacteria is the "main cause of Alzheimer's disease," Dr. Steve Dominy, study author and associate professor at University of California, told Newsweek earlier this month.

But other experts were less convinced. Dr. David Reynolds, a chief scientific officer at the charity Alzheimer's Research U.K., who did not work on the paper, commented: "Previously the P. gingivalis bacteria associated with gum disease has been found in the brains of people with Alzheimer's but it remains unclear what role, if any, it plays in the development of the disease."

He continued: "We know diseases like Alzheimer's are complex and have several different causes, but strong genetic evidence indicates that factors other than bacterial infections are central to the development of Alzheimer's, so these new findings need to be taken in the context of this existing research."

This article has been updated with comment from Dr Sara Imarisio.