Certain drugs that have a strong anticholinergic effect have been associated with an increased risk of dementia in older adults who use them long term, according to a 2019 study in JAMA Internal Medicine. Anticholinergics block a chemical messenger (acetylcholine) involved in the transmission of nerve impulses in the brain.
The study analyzed medical data from more than 58,000 people with dementia and more than 225,000 people without dementia who were at least 55 years old. Researchers noted which drugs the patients with dementia had been prescribed over the one to 11 years prior to diagnosis. Their medications were compared with those of people who did not have dementia.
People who used drugs that have an anticholinergic effect daily for more than three years—including certain drugs for depression, Parkinson’s disease, overactive bladder, and epilepsy—were found to have a 49 percent higher risk of dementia. People who took antidepressants that have an anticholinergic effect had a 29 percent increase in dementia risk, and those who took anticholinergic antipsychotics had a 70 percent increase.
The study was observational, so it’s not certain that the drugs actually caused dementia; it is possible that there were other reasons for the increased risk. However, it is not the first study to find such a link.