Higher Risk of Cognitive Decline Associated with Chronic Constipation

Constipation may be connected to worsening cognitive function, new research finds.

Three prospective studies, with more than 100,000 participants, linked chronic constipation—going three days or more between bowel movements—with cognitive decline.

Compared to people who have a bowel movement every day, researchers found that those with chronic constipation experienced a 73% higher risk of cognitive decline—equivalent to an additional three years of cognitive aging. 

This research, which was presented at the Alzheimer’s Association International Conference, is part of a growing body of evidence that links a person’s gut microbiome to their brain health. The researchers indicate that the buildup of bad bacteria in the gut could potentially be the root cause of declining cognitive health.

In fact, constipation could become one of many factors that prompt clinicians to further evaluate and monitor a person's cognitive health—even if it does not definitively predict cognitive decline,Stewart Parnacott, CRNA, registered nurse, instructor at Baylor College of Medicine, and board member for AARP (American Association of Retired Persons) told Health.

'Early detection of changes in bowel habits may lead to earlier interventions or lifestyle modifications that could impact overall health, including cognitive function,' he said.

Approximately 16% of people worldwide struggle with constipation, which is even more common among mature adults.

This phenomenon is largely due to age-related factors like a lack of exercise and inadequate intake of dietary fiber. Even the use of certain medications can increase the likelihood of constipation. But how does this impact brain health?

Historically, chronic constipation has been linked to inflammation and mood disorders, such as anxiety and depression. So the fact that this new research suggests it may also be connected to cognitive function is not surprising—even though the exact role it plays in brain health is still unclear.

It's important to point out that this research did not show causation, only a correlation, between constipation and cognitive function, Anjali Patel, DO, a cognitive neurologist at the Atlantic Neuroscience Institute at Overlook Medical Center and a member of the Atlantic Medical Group Memory and Cognitive Disorders Center, told Health.

That said, the connection between the two is worth considering when looking at long-term health.

'You don't often think of your gut health directly affecting your brain health but current research is showing a connection,' Emily Spurlock, RD, LT, CLT, a registered dietitian with the Institute for Digestive Wellbeing, told Health.

'It makes sense,' she said. 'One of your major cranial nerves—your vagus nerve—connects your digestive tract to your brain.'

Researchers speculate that the connection between constipation and cognitive decline could be related to the bacteria in the gut—some of which is protective and some of which is not.

Those with infrequent bowel movements and cognitive decline displayed a depletion of the good bacteria that produces butyrate—or the fatty acid that supports your gut barrier and prevents bacteria and other microbes from entering your bloodstream.

'It is possible those with chronic constipation had more bacteria that caused inflammation and less of the bacteria that help break down certain dietary fibers,' Patel said. 'It is important to address the symptoms of constipation to avoid any long-term consequences related to persistent inflammation and chronic disease.'

Right now, the biggest unknown is whether or not a neurological disease, like Alzheimer's, cause bacterial changes in the gut, or whether bacterial changes in the gut (from constipation) are what cause the neurological disease, Geoffrey Eubank, MD, ABPN, a neurologist and OhioHealth System Chief, General Neurology, told Health.

'Association is a bit different than causation,' Eubank explained. 'It is possible that constipation and digestive issues are the way the disease manifests itself.'

At the very least, the new research shows that there is an association.

'[But] it’s not like if someone has digestive issues that the first thing we are thinking is neurological problems,' he said. 'On the other hand, sometimes digestive issues might be the very first inkling that there is a problem—constipation in particular.'

Eubank also acknowledged that while constipation is too common of a symptom to definitively say it's an early indicator of Alzheimer’s, this study may help clinicians down the road—particularly in how gut bacteria and brain health are connected.

According to Parnacott, the gut-brain axis serves as a vital communication pathway between the gut and the central nervous system. 'This two-way communication [system] involves various biochemical signaling, nerve pathways, and the gut microbiome.'

'Researchers are learning more about the role of gut microbiomes in different stages of Alzheimer’s disease,' Patel said. 'This study of the gut-brain axis may aid in new ways to detect and prevent memory loss.'

Though gut bacteria is not currently used as a screening tool, future physicians and researchers may be able to identify certain bad bacteria and address possible cognitive decline before it becomes an issue, Eubank said.

Although experiencing constipation is not a guarantee that you will develop cognitive issues as you age, this study shows it can potentially increase your risk, Spurlock said.

For this reason, it is important to address constipation before it becomes an issue.

'A lot of things we already know are healthy for our brains improve constipation anyway,' Eubank. 'So that’s even more evidence as to why we should be doing these things.'

To begin, prioritize hydration. Spurlock recommends drinking at least 64 ounces of water a day or half your body weight in ounces.

You also can experiment with the amount of fiber you eat. Spurlock explained that while some people thrive on high-fiber diets, others require a much lower dose of daily fiber for regular bowel movements.

A prebiotic and probiotic supplement is another option for preventing constipation.

'Magnesium glycinate also works wonders for many people. You'll need 300 mg to 400 mg. If nothing seems to work, try pelvic floor physical therapy,' Spurlock said. 'I've seen it change lives.'

You also should address your nutrition. Patel said. 'For example, eating a healthy diet such as the Mediterranean diet, which focuses on plant-based foods, has been linked to dementia prevention.'

Engaging in aerobic exercise also can help increase blood flow throughout the body. In fact, exercise can stimulate muscle contractions to help stools pass more easily, she said.

You also should get sufficient sleep and reduce your stress, Patel said. 'The idea is to not only prevent constipation but also promote brain health.'