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People who have chronic constipation (i.e. a bowel movement every three days or more) are at increased risk of cognitive decline, according to new research presented at the Alzheimer’s Association International Conference (AAIC) in Amsterdam.
The study is the first to look at the potential impact of constipation on the ageing brain, and is supported by two other studies which also link gut health to brain health.
Chronic constipation associated with 73% higher odds of cognitive decline
To study the relationship between constipation and cognition, Chaoran Ma, Assistant Professor at University of Massachusetts Amherst, assessed three prospective cohort studies of more than 110,000 people and collected data on bowel movement frequency and cognitive function.
Using data from a subgroup of roughly 12,700 participants, the researchers found that less frequent bowel movements were associated with poorer cognitive function.
Compared to those who had one daily bowel movement, constipated participants (bowel movements every three days or more) had significantly worse cognition, equivalent to three years more of chronological cognitive ageing.
Bowel movement frequency of every three days or less was associated with 73% higher odds of subjective cognitive decline.
The research also revealed that specific levels of gut microbes may affect brain health, and those with fewer bacteria that can produce butyrate and fewer bacteria responsible for digesting dietary fibres had both less frequent bowel movements and worse cognitive function.
However, the study also found that those who had bowel movements more than twice a day were also at a slightly increased risk of cognitive decline.
High levels of certain gut bacteria linked to poorer cognition
Another study has supported the theory that gut health and brain health are linked. The study examined faecal samples and cognitive test scores from more than 1,000 participants in the Framingham Heart Study.
The researchers divided the study group based on participants’ cognitive test scores and compared the microbiomes of participants scoring in the lowest 20% (i.e., poorer cognition) to those who scored higher.
They found individuals with poorer cognition had lower levels of Clostridium and Ruminococcus. The bacteria Alistipes and Pseudobutyrivibrio were found to be highly abundant in those with poor cognition compared to other study participants.
“Further research is needed to better understand the possible neuroprotective effects of some of these bacteria,” said co-author of the study Jazmyn Muhammad. “In the future, it may be possible to manipulate the abundance of these bacteria through diet and pre/probiotics to preserve brain health and cognitive function.”
Healthcare professionals urged to discuss gut health with older patients
Senior investigator of the constipation study, Dong Wang, said these results should prompt healthcare professionals to discuss gut health with older patients, and introduce measures to prevent constipation where appropriate.
“These results stress the importance of clinicians discussing gut health, especially constipation, with their older patients.
“Interventions for preventing constipation and improving gut health include adopting healthy diets enriched with high-fibre and high-polyphenol foods such as fruits, vegetables and whole grains; taking fibre supplementation; drinking plenty of water every day; and having regular physical activity,” Wang said.