They found that having a bowel movement every three days or less frequently is linked to higher levels of cognitive decline as well as some changes in the gut microbiome.
Further studies are needed to determine how these findings might inform treatments and prevention strategies for cognitive decline.
We speak of chronic constipation when a person has a bowel movement less than once every three days or more. It has been linked to various health problems, including anxiety and depression .
Studies show that constipation is a common complication of neurological diseases, such as Parkinson's disease , and is linked to faster progression of Alzheimer's disease.
Better understanding how constipation affects the neurological system – and by extension the brain and cognition – could contribute to the development of treatments and prevention strategies for cognitive decline and related diseases.
Recently, researchers have studied the link between constipation and cognitive decline. They found that having a bowel movement every three days or less frequently was linked to a 73% higher risk of subjective cognitive decline.
These studies were presented at the international conference of the Alzheimer Association in Amsterdam (Netherlands).
Relationship Between Gut Bacteria and Cognition
Other related studies have also shown that increases and decreases in certain gut bacteria are linked to dementia and cognitive decline.
“This research is a first step in determining whether certain types of bacteria in our gut protect our brains from certain types of cognitive diseases ,” Dr. Thomas Gut, assistant professor at the Donald and Barbara Zucker School, told Medical News Today. of Medicine at Hofstra/Northwell, who was not involved in this research.
This research doesn't even address the question of whether promoting certain types of bacterial colonization might protect memory and brain function, but it raises the question and opens the way for further research.
Aging and constipation
For the study, researchers looked at data from 112,753 men and women. The data included information on their bowel movement frequency between 2012 and 2013 as well as self-reports of cognitive function between 2014 and 2017.
A subgroup of 12,696 participants also underwent neuropsychological testing under the supervision of the researchers. Participants also provided stool samples to assess levels of different bacteria.
Ultimately, the researchers found that people who had bowel movements every three days or more had significantly worse cognition – equivalent to 3 years of additional aging – than those who had bowel movements once a day.
These people also had a 73% higher risk of subjective cognitive decline and fewer butyrate-producing microbes, a marker of healthy bacteria that help digest dietary fiber.
The researchers also found that people who had bowel movements more than twice a day had a slightly increased risk of cognitive decline and tended to have more pro-inflammatory species in their microbiome.
The risks associated with constipation
The researchers concluded that less frequent bowel movements are linked to impaired cognitive function and that this link may be explained by changes in the gut microbiome.
Two other recent studies have further examined specific gut bacteria linked to an increased risk of dementia , as well as gut bacteria that may have a neuroprotective effect.
In the first study, researchers evaluated data from 140 cognitively healthy people, with an average age of 56 years. The data included stool samples and measurements of the biomarkers of Alzheimer's disease proteins, amyloid and tau, obtained by positron emission tomography (PET).
They found that higher levels of amyloid and tau were linked to lower levels of gut bacteria Butyricicoccus and Ruminococcus and higher amounts of Cytophaga and Alistipes. They noted that Butyricicoccus and Ruminococcus might have neuroprotective effects.
In a press release, the researchers suggest that reducing certain bacteria may increase gut permeability and the transport of certain metabolites to the brain, which may, in turn, increase the accumulation of amyloid-beta proteins. and tau.
The next step in research, they say, would be to test whether introducing, increasing, or reducing certain gut microbes could beneficially alter amyloid and tau levels. If so, it could help identify potential new therapeutic approaches for Alzheimer's disease.
In the second study, researchers looked at stool samples and cognitive test scores from 1,014 participants with an average age of 52. They divided the cohort into groups based on their cognitive test scores and compared the lowest 20% to the highest 20%.
Ultimately, they found that people with the lowest cognitive abilities had lower levels of Clostridium and Ruminococcus and higher levels of Alistipes and Pseudobutyrivibrio than the other participants.
The researchers note that additional research is needed to better understand the possible neuroprotective effects of these bacteria. They add, however, that in the future, it may be possible to manipulate their abundance through diet and prebiotics to preserve brain health and cognitive function.
Cognitive decline or not?
Medical News Today spoke with Dr. J. Wes Ulm, bioinformatics science resource analyst and biomedical data specialist at the National Institutes of Health, about its limitations.
According to him, while the studies show a correlation between constipation and cognitive decline, they do not demonstrate a causal link because of their preliminary nature.
“Similarly, it is unclear whether there is a causal relationship between certain dietary practices, such as fiber intake or use of probiotics or prebiotics , and observed outcomes,” he said. points out.
"Furthermore, most observations of cognitive decline were subjective in the associated patient population, and only a relatively small sample was subjected to objective testing in various ways to more reliably substantiate such findings," added the Dr Ulm.
Health habits: essential key to physical and mental health
Dr. Ulm noted that while the causes and mechanisms are unclear, other studies show that factors contributing to chronic constipation, such as insufficient fiber intake, low fluid intake and sedentary lifestyle , are also linked to inflammation and neuropsychiatric conditions.
He added that while nutritional recommendations can be frustrating because they change frequently based on scientific advances, overall, improving general health habits can reduce the risk of cognitive decline. These habits include increasing fruit, vegetable, fiber and fluid intake, and exercising more frequently.
Dr. Ulm concludes that it would be interesting to see what will come out of this research – from basic treatments to reduce constipation to targeted changes to the gut microbiome – and how they might help prevent dementia and cognitive decline in general.