Cognitive decline: Does chronic constipation factor in?

Evan Walker
Evan Walker TheMediTary.Com |
illustration of brain shape made out of metal cogs on a black backgroundShare on Pinterest
New research links constipation with a higher risk of cognitive decline. Image credit: tifonimages/Getty Images.
  • In a series of new studies, researchers investigated the link between constipation and cognitive decline.
  • They found that one bowel movement every 3 days or less frequently is linked to higher levels of cognitive decline alongside certain changes in the gut microbiome.
  • Further studies are needed to see how these findings could inform treatments and prevention strategies for cognitive decline.

Around 16% of the global population experiences constipation. Risk factors for constipation include low levels of physical activity, female gender, residential location, and medical conditions, including depression, hemorrhoids, and some cardiovascular, gastrointestinal, and musculoskeletal conditions.

Chronic constipation occurs when a person has fewer than one bowel movement every 3 or more days. It has been linked to various health conditions, including anxiety and depression.

Studies show that constipation is a common complication of neurological conditions, such as Parkinson’s disease, and that it is linked to faster Alzheimer’s disease progression.

Understanding more about how constipation affects the neurological system — and the brain and cognition by extension — could aid the development of treatments and prevention strategies for cognitive decline and related conditions.

Recently, researchers investigated the link between constipation and cognitive decline. They found that having a bowel movement every 3 days or less frequently was linked to a 73% higher chance of subjective cognitive decline.

The studies were presented at the Alzheimer’s Association International Conference in Amsterdam, Netherlands, and online.

Two other recent studies further investigated specific gut bacteria linked to increased dementia risk, as well as which gut bacteria may be neuroprotective.

In the first study, researchers assessed data from 140 cognitively Healthy individuals with an average age of 56 years. Data included fecal samples and measures of Alzheimer’s protein biomarkers amyloid and tau from PET brain scans.

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 suggested that the reduction of certain bacteria may increase gut permeability and the transport of certain metabolites to the brain, which could, in turn, increase the buildup of amyloid-beta and tau proteins.

They said that a next step for research would be to test whether introducing, increasing, or reducing certain gut microbes could beneficially change levels of amyloid and tau. If so, this could help in identifying potential new therapeutic approaches for Alzheimer’s.

In the second study, researchers examined fecal samples and cognitive test scores from 1,014 participants with a mean age of 52 years old. They split the cohort into groups according to their cognitive test scores and compared those scoring in the lowest 20% to those scoring the highest.

Ultimately, they found that individuals with the poorest cognition had lower levels of Clostridium and Ruminococcus and higher levels of Alistipes and Pseudobutyrivibrio than other participants.

The researchers noted that more research is needed to better understand the possible neuroprotective effects of these bacteria. However, they added that in the future, it may be possible to manipulate their abundance through diet and prebiotics to preserve brain health and cognitive function.

Dr. Ulm noted that although causation and mechanisms remain unclear, other studies show that contributors to chronic constipation, such as insufficient fiber intake, low fluid intake, and a sedentary lifestyle, are also linked to inflammation and neuropsychiatric conditions.

He added that while nutritional recommendations can be frustrating as they shift frequently according to scientific advances, overall, improving general health habits may reduce the risk of cognitive decline. Such habits include increasing the consumption of fruit, vegetables, fiber, and fluids and exercising more frequently.

Dr. Ulm concluded that it would be interesting to see what comes from this research — from basic treatments to reduce constipation to targeted modifications of the gut microbiome — and how these may help prevent dementia and cognitive decline in general.

Share this Article