Among more than 500,000 middle-aged or older adults in the UK Biobank, those who reported regular laxative use had a 51% increased risk of dementia due to any cause, compared with their counterparts who did not regularly use laxatives.
Individuals who used only osmotic laxatives had a 64% increased risk, compared with peers who did not use laxatives, while those using one or more types of laxatives, including bulk-forming, stool-softening, or stimulating laxatives, had a 90% increased risk.
“Constipation and laxative use are common among middle-aged and older adults,” study investigator Feng Sha, PhD, with the Chinese Academy of Sciences in Guangdong, China, said in a news release.
“However, regular laxative use may change the microbiome of the gut, possibly affecting nerve signaling from the gut to the brain or increasing the production of intestinal toxins that may affect the brain,” Dr. Sha noted.
The study was published online in Neurology.
Robust link
The findings are based on 502,229 people (54% women; mean age, 57 at baseline) from the UK biobank database. All were dementia-free at baseline.
A total of 18,235 participants (3.6%) said they used over-the-counter laxatives regularly, which was defined as using them most days of the week during the month before the study.
Over an average of 9.8 years, dementia was recorded in 218 (1.3%) of those who regularly used laxatives and in 1,969 (0.4%) of those did not.
After adjusting for factors such as age, sex, education, other illnesses, medication use, and a family history of dementia, regular use of laxatives was significantly associated with increased risk of all-cause dementia (adjusted hazard ratio, 1.51; 95% confidence interval, 1.30-1.75) and vascular dementia (aHR, 1.65; 95% CI, 1.21-2.27), with no significant association observed for Alzheimer’s disease (aHR, 1.05; 95% CI, 0.79-1.40).
The risk of dementia also increased with the number of laxative types used. All-cause dementia risk increased by 28% (aHR, 1.28; 95% CI, 1.03-1.61) for those using a single laxative type and by 90% (aHR, 1.90; 95% CI, 1.20-3.01) for those using two or more types, compared with nonuse.
Among those who reported using only one type of laxative, only those using osmotic laxatives had a statistically significant higher risk of all-cause dementia (aHR, 1.64; 95% CI, 1.20-2.24) and vascular dementia (aHR, 1.97; 95% CI, 1.04-3.75).
“These results remained robust in various subgroup and sensitivity analyses,” the investigators report.
They caution that they had no data on laxative dosage and so they were unable to explore the relationship between various laxative dosages and dementia risk.
Interpret with caution
Commenting on the findings for this news organization, Heather Snyder, PhD, vice president of medical and scientific relations at the Alzheimer’s Association, said the results are “interesting and demonstrate an association between laxative use and later life risk of dementia.”
However, “there is no proven causation, and there are some caveats,” Dr. Snyder said. “It’s unclear what may be driving this association, though other lines of research have suggested a linkage between our overall gut health, our immune system, and our brain health.”
Dr. Snyder said it’s also worth noting that the data came from the UK Biobank, which, “while a wealth of information for research purposes, is not representative of other countries. More research is needed.”
The Alzheimer’s Association is leading a 2-year clinical trial, U.S. Pointer, to examine the impact of behavioral interventions on the gut-brain axis to “better understand how our gut health may affect our brains,” Dr. Snyder told this news organization.
“While we await the results of that study, people should talk to their doctor about the risks and benefits of laxatives for their health, as well as discuss alternative methods of alleviating constipation, such as increasing dietary fiber and drinking more water,” she advised.
The study was funded by the National Natural Science Foundation of China, Shenzhen Science and Technology Program, and the Chinese Academy of Sciences. The authors and Dr. Snyder have disclosed no relevant financial relationships.
A version of this article originally appeared on Medscape.com.