Can laxatives increase your risk of dementia?

Most people have experienced constipation at some point in their lives and it can become more common with age. To ease constipation, people may reach for laxatives that are available over-the-counter. But a recent study reported that people who regularly used laxatives had a higher risk of dementia [1].

Findings come from the UK Biobank, a large cohort study of over 500,000 participants who were 40-69 years old, with no dementias at the start of the study. Participants answered detailed questionnaires on demographics, lifestyle, health status, and the use of common over-the-counter medications including laxatives. Laxatives were further categorized by subtypes: stool softeners, bulk-forming laxatives, osmotic laxatives, and stimulant laxatives. At the beginning of the study, only 3.6% of participants reported regular use of laxatives, defined as using laxatives most days of the week during the month prior to enrolling into the study. Participants were followed for approximately ten years.

After controlling for many sociodemographic, lifestyle, and health factors, people who regularly used laxatives had a 51% higher risk for dementia compared to those who did not regularly use laxatives. When examining different types of dementia, the risk for vascular dementia (but not Alzheimer’s disease) was higher in people who regularly used laxatives compared to those who did not. People who regularly used one kind of laxative had a 28% higher risk for dementia, while those who regularly used a combination of two or more laxatives had a 90% higher risk. When examining the different types of laxatives, dementia risk was 64% higher in people who regularly took osmotic laxatives (which draw water into the intestine) compared to those who did not regularly use any laxatives. Other types of laxatives (stool softeners, bulk-forming laxatives, and stimulant laxatives), when taken alone, were not associated with a higher risk of dementia.

Although these findings may be alarming, this study was an observational study aimed at finding associations—and it was not designed to prove cause and effect. In other words, this study does not prove that laxatives are the direct cause of increased dementia risk, or stopping the use of laxatives could protect against dementia. People who need to regularly use laxatives may not be getting enough physical activity, which is one of the major risk factors for dementia. Also, regular users of laxatives may not be consuming enough fiber in their diet, including vegetables and fruits, which are key for a brain-healthy diet. Eating a healthy diet including large amounts of vegetables and fruits is associated with better brain health and lower dementia risk [2]. Being dehydrated, which can cause constipation, can also put a strain on cognitive function and brain health [3].

The association between regular laxative use and higher dementia risk is a new finding and is not consistent with a previous smaller observational study that had found an association between the use of a specific type of osmotic laxative (magnesium oxide) and a lower risk of dementia [4]. Thus, further studies are needed to reconcile these discrepancies. There are many unanswered questions. If laxatives, particularly osmotic laxatives, play a role in dementia, what are the mechanisms? One possibility, which has been demonstrated in laboratory studies, is that laxatives can significantly disrupt the gut microbiome composition [5], which consists of 100 trillion bacteria (some are good, others are neutral or bad). The gut microbiome plays an important role in regulating inflammation and metabolism [6], and alterations in the makeup of the microbiome can directly impact brain health. However, more research is needed to determine if laxatives are truly causing heightened dementia risk, and if so, their precise mechanisms. In the meantime, getting enough exercise, eating a healthy diet, and staying hydrated are the first recommendations for constipation, and these healthy habits have the added benefit of promoting brain health.

1. Yang Z, Wei C, Li X et al. (2023) Association Between Regular Laxative Use and Incident Dementia in UK Biobank Participants. Neurology.
2. Ballarini T, Melo van Lent D, Brunner J et al. (2021) Mediterranean Diet, Alzheimer Disease Biomarkers and Brain Atrophy in Old Age. Neurology 96, e2920-2932.
3. Wittbrodt MT, Millard-Stafford M (2018) Dehydration Impairs Cognitive Performance: A Meta-analysis. Medicine and science in sports and exercise 50, 2360-2368.
4. Tzeng NS, Chung CH, Lin FH et al. (2018) Magnesium oxide use and reduced risk of dementia: a retrospective, nationwide cohort study in Taiwan. Current medical research and opinion 34, 163-169.
5. Tropini C, Moss EL, Merrill BD et al. (2018) Transient Osmotic Perturbation Causes Long-Term Alteration to the Gut Microbiota. Cell 173, 1742-1754 e1717.
6. Chandra S, Sisodia SS, Vassar RJ (2023) The gut microbiome in Alzheimer's disease: what we know and what remains to be explored. Molecular neurodegeneration 18, 9.

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