Chronic constipation is associated with an increased risk of cognitive decline. The finding adds to a growing body of evidence suggesting that gut health plays a role in dementia and related illnesses, such as Alzheimer’s disease.
To understand how constipation relates to brain health, Chaoran Ma at the University of Massachusetts Amherst and her colleagues analysed data from more than 110,000 adults. Everyone reported the frequency of their bowel movements between 2012 and 2013. They also assessed changes in their own memory, attention and other aspects of cognition over a two- to four-year period with a survey.
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The researchers found that those with chronic constipation – having bowel movements every three days or more – had worse cognitive function compared with participants who had daily bowel movements, equivalent to three additional years of cognitive ageing.
Chronic constipation was associated with a 73 per cent increased risk of cognitive decline, and having more than one bowel movement a day was associated with a 37 per cent increased risk.
Genetic analysis of stool samples collected from 515 participants revealed that those with worse cognition and chronic constipation had fewer gut bacteria for digesting dietary fibre. They also had more gut bacteria known to cause inflammation compared with other participants.
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These differences in gut bacteria may explain why chronic constipation is linked to declining brain health, says Ma, who presented these findings at the Alzheimer’s Association International Conference in the Netherlands on 19 July. For instance, persistent inflammation is known to damage neurons in people with Alzheimer’s disease.
“However, our study was not designed to test the causal relationships between bowel movements, the gut microbiome and cognition,” she says. Even so, these findings further support the notion that gut health is closely related to brain health.
“Our body systems are all interconnected. When one system is malfunctioning, it impacts other systems,” said Heather Snyder at the Alzheimer’s Association in Chicago in a statement. “Eating well and taking care of your gut may be a pathway to reduce the risk of dementia,” she said.
