(CNN)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.