Researchers say they’ve found a possible link between regular laxative use and a person’s risk of dementia, but experts note that the research is very early and should be interpreted with caution.
According to the researchers, from medical institutions across China as well as the University of Cambridge and Harvard Medical School, constipation affects about 20% of the general population and about 70% of people in nursing homes, and most people with constipation are treated with one of two versions of over-the-counter laxatives.
The study, published Wednesday in the American Academy of Neurology’s medical journal, Neurology, suggests that a potential dementia link is strongest with osmotic laxatives, which draw water into stool to make it softer and easier to pass. The other major kind, stimulant laxatives, increases muscle contractions along the stool mass.
The study included about 10 years of self-reported data from 476,219 adults ages 40 and 69 in the UK. At the start, the study authors identified the participants’ health status and lifestyle factors, including their exposure to over-the-counter laxatives. About 3.6% of the participants reported using laxatives most days of the week for the previous four weeks.
These regular users were more likely to be women, have less education, have a chronic illness, and regularly take anticholinergic and opioid drugs. “The prevalence of stroke, high blood pressure, depression, poor overall self-health rating, and the uptake of calcium channel blockers, statins, and steroid drugs were higher in regular than non-regular users,” the study says.
The researchers found that 2,187 participants had a diagnosis of all-cause dementia, which includes Alzheimer’s disease and vascular dementia, by the end of the study period.
“Regular use of laxatives was associated with a higher risk of all-cause dementia, particularly in those who used multiple laxative types or osmotic laxative,” they wrote in the study.
Dementia was diagnosed in 1.3% of the participants who regularly used laxatives and 0.4% of those who didn’t report regular laxative use.
Dr. Richard Isaacson, a preventative neurologist at the institute for Neurodegenerative Diseases of Florida, says the findings are interesting but only speculative.
“Further study is absolutely warranted to make a definitive impact on clinical practice,” said Isaacson, who was not involved in the study.
The researchers offered one explanation for the finding, which begins with the composition of the microbiome, the trillions of microorganisms that live in the gut.
They said that an osmotic laxative has a lasting impact on the microbiome and could affect the production of neurotransmitters needed for normal cognitive function. An osmotic laxative may also increase the production of intestinal toxins, they wrote.
Laxatives may also disrupt the epithelial barrier, which regulates nutrient absorption and helps deliver necessary substances to the central nervous system.
The study’s limitations include that patient data was self-reported and could have been inaccurately noted, and that there was limited information on possible confounders like fiber intake and severity of constipation.
Dr. Ali Rezaie, director of the GI Motility Program at Cedars-Sinai Medical Center, said that he’s skeptical of the findings and that the study lacks one main component needed to accurately draw an association between regular laxative use and dementia: enough data.
“Laxatives do change the microbiome, but we don’t have data to suggest that those changes caused by the laxatives are the same changes that we see in the study of dementia,” said Rezaie, who was not involved in the research. “That is a big leap that will take decades of studying to figure out.”
He says that the study period was not long enough to draw concrete evidence and that the foundational participant data does not accurately represent what he sees in his practice.
The study equates the amount of participants who used laxatives regularly to the number who experienced constipation, but the two groups may not always overlap.
“How come the prevalence of constipation in their study was only 3%?” he asked. “This simply tells me that they did not pick up all of the constipation patients, they only picked up patients who mentioned over-the-counter laxatives they were taking regularly. … It’s very unusual to find only 3% of a population constipated.”
Isaacson also noted the lack of participant data, especially related to the diversity of participants.
“From a health equity perspective, it’s important to say that the specific study population was 90% White,” he said. “Broader conclusions based on a more diverse population really have to be withheld.”
Isaacson and Rezaie came to a similar conclusion: More research is needed, and the potential link isn’t strong enough to change medical practice.
“We don’t really want to be telling people it’s time to stop their laxative because you’re going to have dementia. That is the wrong message,” Isaacson said.
Rezaie said he worries that his patients may be overly concerned about the possibility of dementia and avoid the laxatives needed for certain procedures.
“This may even affect our colon cancer screening,” he said.