An illustration of a glowing brain within a woman's abdomen. Credit: Getty Images

UMass Amherst Assistant Professor Presents New Research Linking Abnormal Intestinal Function and Cognitive Decline

The study’s findings link microbiome and brain function

Nutritional epidemiologist Chaoran Ma of the University of Massachusetts Amherst presented today, July 19, at the Alzheimer’s Association’s International Conference in Amsterdam and online, new research that associates chronic constipation with cognitive decline.

“Our study provides first-of-its-kind evidence of abnormal intestinal function being linked to cognitive decline. Specifically, we found that less frequent bowel movements were associated with poorer cognitive function,” says Ma, assistant professor in the School of Public Health and Health Sciences and lead author of the study, which is under review for publication. She was one of several researchers discussing results of new studies shedding new light on cognitive decline during the Alzheimer’s Association’s conference.

Ma and team’s findings are based on an analysis of three prospective cohorts of 112,753 women and men from the Nurses’ Health Study, the Nurses’ Health Study II and the Health Professionals Follow-up Study

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 the CogState neuropsychological battery for objective cognitive assessment between 2014 and 2018.

Chaoran Ma

Our study provides first-of-its-kind evidence of abnormal intestinal function being linked to cognitive decline. Specifically, we found that less frequent bowel movements were associated with poorer cognitive function.

Chaoran Ma, assistant professor in the UMass Amherst School of Public Health and Health Sciences

“Compared to those with bowel movements once daily, constipated participants (bowel movements every three-plus days) had significantly worse cognition, equivalent to 3.0 years more of cognitive aging,” Ma says. “We also found a slightly increased risk of cognitive decline in those who had bowel movements more than twice a day.”

Ma conducted the research when she was a research fellow at Brigham and Women’s Hospital and Harvard Medical School, working with senior author Dr. Dong Wang, an assistant professor at Harvard Medical School, Brigham and Women’s Hospital and Harvard T.H. Chan School of Public Health.

In a subgroup of 515 women and men, the researchers also looked at the role of the gut microbiome in the association between bowel movement frequency and cognitive function. They found that bowel movement frequency and subjective cognition were significantly associated with the overall variation of the gut microbiome and specific microbial species.

“This research adds further evidence for a link between the microbiome and gastrointestinal function with cognitive function,” Ma says. “Our findings not only support considering constipation as a risk factor for cognitive decline, but also provide further evidence for the link between microbiome and brain function.”

About 16% of the world’s population experiences chronic constipation, with older adults facing higher rates of constipation due to such age-related factors as fiber-deficient diets, lack of exercise and the use of constipating drugs to treat other medical conditions. Chronic constipation is also associated with inflammation, hormonal imbalances and anxiety/depression.

“Our microbiome study found that individuals with specific microbial profiles in the gut, i.e., more bacteria that can cause inflammation and fewer bacteria responsible for digesting dietary fibers, had less frequent bowel movements and worse cognitive function,” Ma says. “In addition, unhealthy microbial profiles in the gut may explain the association between abnormal intestinal function and cognitive decline.”

The researchers say the studies’ findings suggest individuals should pay attention to any symptoms of abnormal intestinal function.

“These results stress the importance of clinicians discussing gut health, especially constipation, with their older patients,” Wang says. “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.”

A bowl of mushroom risotto on a cutting board with sliced mushrooms. Credit: Getty Images

Adding more of the edible fungi into your diet may be one way to counteract the health risks associated with the Western-style diet (WSD), which often features an abundance of fatty foods and added sugars.