Chronic Constipation Linked to Cognitive Decline

Megan Brooks

July 19, 2023

Chronic constipation may be associated with worsening cognitive function, new data from three prospective cohort studies with more than 100,000 adults show.

Compared to individuals who have a bowel movement once daily, adults with constipation who have a bowel movement every 3 days or more had significantly worse cognition that was commensurate with an additional 3 years of chronologic cognitive aging, the investigators found.

"We should watch for symptoms of abnormal intestinal function, especially constipation, in older individuals, as these symptoms may hint at a higher risk of cognitive decline in the future," study investigator Chaoran Ma, MD, PhD, former research fellow at Brigham and Women's Hospital and Harvard Medical School and current assistant professor at the University of Massachusetts Amherst, told Medscape Medical News.

The findings were presented at the Alzheimer's Association International Conference (AAIC) 2023.

Prevent Constipation, Improve Brain Health?

It's estimated that 16% of the world's population suffers from constipation. The problem is more common in older adults, owing to age-related factors such as a lack of dietary fiber and exercise and the use of constipating drugs to treat other medical conditions.

Chronic constipation — defined as having bowel movements every 3 days or more — has been associated with long-term health problems, such as inflammation, hormonal imbalances, anxiety, and depression.

However, few studies have investigated variations in intestinal motility and cognitive function.

"Our study provides first-of-its-kind evidence that examined a wide spectrum of bowel movement frequency, especially an analysis of the more frequent end, in relation to cognitive function," Ma said.

The analysis involved data from 112,753 women and men from the Nurses' Health Study (aged 30 – 55), the Nurses' Health Study II (aged 25 – 42), and the Health Professionals Follow-up Study (aged 40 – 75).

Data on participants' bowel movement frequency was collected between 2012 and 2013, and self-assessments of cognitive function were obtained from 2014 to 2017. A subgroup of 12,696 participants completed a standard neuropsychological test battery for objective cognitive assessment between 2014 and 2018.

The results show that bowel movement frequency was associated with overall objective cognitive function and learning and working memory in an inverse J-shape dose-response manner (both P for nonlinearity < .05).

Compared to adults who had one bowel movement daily, those who only had a bowel movement every 3 or more days had significantly worse cognition, equivalent to 3 yearsof additional aging (95% CI, 1.2 – 4.7).

The researchers also observed similar J-shape dose-response relationships of bowel movement frequency with the odds of subjective cognitive decline and the likelihood of having more subjective cognitive complaints over time.

Compared to once-daily bowel movements, having bowel movements every 3 or more days was associated with a greater likelihood of subjective cognitive decline (odds ratio, 1.73; 95% CI, 1.60 – 1.86).

These relationships were generally consistent across the three cohorts and subgroups.

"These results stress the importance of clinicians discussing gut health, especially constipation, with their older patients," senior investigator Dong Wang, MD, ScD, with Harvard Medical School and Brigham and Women's Hospital, Boston, said in a conference statement.

"Interventions for preventing constipation and improving gut health include adopting healthy diets enriched with high-fiber and high-polyphenol foods such as fruits, vegetables, and whole grains; taking fiber supplementation; drinking plenty of water every day; and having regular physical activity," Wang added.

The researchers also explored the role of the gut microbiome in the association between bowel movement frequency and cognitive function in a subgroup of 515 women and men.

They found that bowel movement frequency and subjective cognition were significantly associated with the overall variation of the gut microbiome (both P < .005) and specific microbial species.

"This research adds further evidence for a link between the microbiome and gastrointestinal function with cognitive function," Ma told Medscape Medical News.

Interconnected Systems

Commenting on the study in a conference statement, Heather M. Snyder, PhD, vice president of medical and scientific relations at the Alzheimer's Association, noted that "our body systems are all interconnected. When one system is malfunctioning, it impacts other systems. When that dysfunction isn't addressed, it can create a waterfall of consequences for the rest of the body."

Snyder cautioned, however, that "there are a lot of unanswered questions about the connection between the health of our digestive system and our long-term cognitive function. Answering these questions may uncover novel therapeutic and risk-reduction approaches for Alzheimer's and other dementias."

In an interview with Medscape Medical News, Percy Griffin, PhD, director of scientific engagement at the Alzheimer's Association, noted that the US Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk (US POINTER), is evaluating the impact of behavioral interventions on the gut-brain axis.

"We want to better understand how engaging in healthier habits can impact microorganisms in the gut and how changes in gut bacteria relate to brain health," Griffin said.

The study was funded by the National Institutes of Health. Ma, Wang, Snyder, and Griffin have no relevant disclosures.

Alzheimer's Association International Conference (AAIC) 2023: Abstract 73719. Presented July 19, 2023.

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