Excessive laxative use and dementia

My mother was an avid book collector. As a teen, I would browse the book shelves in our home looking for interesting nuggets. One of my favorite finds was The Importance of Living by the Chinese philosopher Lin Yutang. The book was originally published in 1937, but I am not certain when our copy was published.  In my small high school in the 1960s, we had a meeting every morning for announcements by the faculty and inspirational readings by students on the “chapel” committee. When my turn came to read, it was often an excerpt from The Importance of Living. The only adage I remember now is “If one’s bowels move, one is happy, and if they don’t move, one is unhappy. That is all there is to it.” At the time I shared this wisdom with the school, I was probably trying to be cheeky if not downright scatological, but I have realized over the years that there is some truth to that quote. On the dark side, an obsession with regular bowel movements can encourage an overuse of laxatives leading to unintended consequences.

The gut microbiota refers to the organisms normally living in our gut.  These bacteria, viruses, fungi, yeasts, and bacteriophages start to colonize the gut at birth, and reach a stable population at about age three. Throughout life, excessive use of some antibiotics and laxatives can disrupt the composition of the gut microbiota leading to problems not only in the gut but also throughout the body, including the brain.

A recent study in Neurology provides the best data yet on the effect of long term, chronic laxative use on the chance of getting dementia. In this 10-year study of 502,229 UK Biobank participants, the regular use of laxatives was associated with higher risk of all-cause and vascular dementia. At the start of the study, the average age was 57 years, and none of the participants had dementia.  Over the subsequent 10 years, 1.3% of those who regularly used laxatives developed dementia. Regular use was defined as taken almost every day. Only 0.4% of those not regularly using laxatives developed dementia. After adjusting for factors such as age, sex, education, other illnesses and medication use, participants who regularly used laxatives were 1.51 times more likely to develop dementia compared to people who did not regularly use laxatives. The risk of dementia also increased with the number of laxative types used at the same time. For people using one type of laxative, the hazard ratio was 1.28 compared to 1.90 for people taking two or more types of laxatives. Osmotic laxatives (e.g., polyethylene glycol, milk of magnesia, or lactulose) were the worst offenders when used regularly, even when taken alone. The authors conclude that “instead of regular use of laxatives, constipation can be mitigated most of the time by lifestyle changes, such as increasing fluid intake, dietary fiber, and activity levels, which may also benefit brain health.” Lin Yutang might well have approved of such advice.