He chronic constipation It is a digestive disorder that affects around 16% of the world population and is characterized by defecating less than three times a week, but also by expelling the stool with effort, that the stool is hard, dry and small, or by experiencing the sensation of incomplete evacuation. It is not a disease in itself, but a symptom that may be associated with health problems, a sedentary lifestyle, the consumption of some drugs, or an inadequate diet, among other factors.
This alteration of intestinal transit has been associated with long-term health problems such as inflammation, hormonal imbalances and anxiety or depression, but now a new study has also chronic constipation linked to worse cognitionequivalent to three years of brain aging, based on results presented at the Alzheimer’s Association® International Congress (AAIC® 2023), in Amsterdam, The Netherlands, and online. These findings add to previous scientific evidence that link a healthy gut to a healthy brain.
Two additional studies have identified Specific Gut Bacteria Linked to Higher Dementia Risk, as well as intestinal bacteria that may be neuroprotective. Previous research has also linked a healthy balance in the composition of the gut microbiome, which is the set of microorganisms that live in our digestive tract, with other vital body functions.
Constipated individuals (with a bowel movement every three days or more) had significantly worse cognition, equivalent to three more years of chronological cognitive aging.
“All of our body systems are interconnected,” says Heather M. Snyder, vice president of medical and scientific relations for the Alzheimer’s Association. “When one system malfunctions, it affects other systems. When that dysfunction isn’t addressed, it can create a cascade of consequences for the rest of the body.” “There are still many unanswered questions about the connection between the health of our digestive system and our long-term cognitive function,” adds Snyder. “Answering these questions can uncover New therapeutic and risk reduction approaches for the Alzheimer and others dementias”.
To further study this relationship in depth, the Alzheimer’s Association’s US Study to Protect Brain Health through Lifestyle Intervention to Reduce Risk (US POINTER), with support from the US National Institutes of Health, examines the impact of behavioral interventions on the gut-brain axis to better understand how healthier habits influence gut microorganisms and how changes in gut bacteria are related to gut health. brain.
While we wait for their results, she says, “people should talk to their doctor about their digestive health and ways to relieve constipation, such as increasing dietary fiber intake and drinking more water.” “Eating well and taking care of the intestine may be a way to reduce the risk of dementia.”
The risks of having a bowel movement every three days or more
To study how healthier habits influence gut microorganisms and how changes in gut bacteria are related to brain health, the Dr. Charon Ma, an adjunct professor at the University of Massachusetts Amherst, evaluated three prospective cohort studies involving more than 110,000 people in the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-up Study. Ma and team collected data on bowel movement frequency from all participants in 2012-2013 and their self-assessments of cognitive function from 2014-2017; objective cognitive function was measured between 2014 and 2018 in a subgroup of 12,696 participants.
The researchers found that a lower frequency of bowel movements was associated with poorer cognitive function. Compared with those who had a bowel movement once a day, the constipated participants (who had a bowel movement every three days or more) had significantly worse cognition, equivalent to three more years of chronological cognitive aging. Bowel movement frequency every three days or less was associated with a 73% increased propensity for subjective cognitive impairment.
Other relevant findings were:
- A slightly higher risk of cognitive decline in those who moved more than twice a day.
- Individuals with certain specific levels of microbes in the gut (fewer bacteria capable of producing butyrate and less bacteria responsible for digesting food fibers) had less frequent bowel movements and poorer cognitive function.
“These results underscore the importance of clinicians discussing gut health, especially constipation, with their older patients,” said study principal investigator Dr. Dr. Dong Wang, Adjunct Professor at Harvard Medical School, Brigham and Women’s Hospital, and Harvard TH Chan School of Public Health. “Interventions to prevent constipation and improve gut health include adopt healthy diets enriched with high fiber foods and polyphenolssuch as fruits, vegetables, and whole grains; take fiber supplements; drink plenty of water every day; and engage in regular physical activity.
Connection Between Gut Bacteria and Alzheimer’s Biomarkers
Studies carried out with mouse models of Alzheimer’s have shown connections between the accumulation of amyloid beta and the levels of certain intestinal microbiota, but it is unknown if the accumulation of Alzheimer’s biomarkers is associated with changes in the human intestinal microbiota.
To investigate this possible association, Yannick Wadopa postdoctoral fellow at the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health San Antonio, and colleagues used fecal samples and cognitive measures from 140 cognitively healthy people with an average age of 56 years from the Framingham Heart Study to assess the relationship between gut microbiome composition and amyloid and tau-PET measures.
They found that elevated levels of amyloid and tau detected through brain studies were associated with lower levels of gut bacteria. Butyricicoccus y Ruminococcus and higher amounts of Cytophaga y Alistipes. The investigator’s functional analysis suggested that Butyricicoccus y Ruminococcus may have neuroprotective effects.
“These findings are beginning to reveal more specific connections between our gut and our brain,” Wadop says. “For example, we believe that the reduction of certain identified bacteria can increase intestinal permeability and the transport of toxic metabolites in the brainthus increasing the deposition of beta-amyloid and tau.
“A possible next step is to see if introducing and increasing or reducing specific gut microbes could beneficially change amyloid and tau levels,” adds Wadop. “This could help us identify potential new therapeutic approaches for Alzheimer’s.”
Good and Bad Gut Bacteria for the Brain
To better understand the relationship between the intestinal microbiome and cognitionn in middle-aged and older adults, Jazmyn Muhammada research associate at UT Health San Antonio’s Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, and her colleagues examined fecal samples and cognitive test scores from more than 1,000 participants in the Framingham Heart Study with an average age of 52 years, and 55% women.
The study group was divided based on the participants’ cognitive test scores, and the microbiomes of participants with scores in the bottom 20% (i.e., with the worst cognition) were compared to those with the highest scores. They found that people with poorer cognition had lower levels of Clostridium y Ruminococcus and that the bacteria Alistipes y Pseudobutyrivibrio they were very abundant in people with poor cognition compared to other study participants.
“Further research is needed to better understand the potential neuroprotective effects of some of these bacteria,” recommends Muhammad. “In the future it might be possible to manipulate the abundance of these bacteria through diet and prebiotics and probiotics to preserve brain health and cognitive function”.