It's tempting to pop a Benadryl when you can't sleep. But seemingly benign over-the-counter drugs taken for insomnia and other common conditions, such as allergies, motion sickness or incontinence, can damage the aging brain, according to research published in the journal Neurology.
The drugs, called anticholinergics, work by blocking acetylcholine, a nervous system neurotransmitter. They're widely used, especially by the elderly and sold under the names Benadryl, Dramamine, Exedrin PM, Nytrol, Sominex and Tylenol PM. Some anticholinergics, such as Paxil, Detrol, Demerol and Elavil, are available only by prescription. (Here’s a list of medications with anticholinergic effects.)
In a six-year observational study, researchers from Indiana University School of Medicine, the Regenstrief Institute and Wishard Health Services evaluated 1,652 Indianapolis area African-Americans over the age of 70 who had normal cognitive function when the study began. The study was longitudinal, which means it collected data on people at more than one time point and analyzed the change.
The scientists monitored cognition and tracked all over-the-counter and prescription medications taken by study participants. They found that consistently taking one anticholinergic "significantly increased an individual’s risk of developing mild cognitive impairment" while taking two of the drugs doubled the risk.
The finding was especially significant for African Americans, who are already known to be at high risk for developing cognitive impairment, said lead author Noll Campbell, a clinical pharmacist with Wishard Health Services. But the results can be generalized to other races, the researchers said.
Indiana University geriatrician Malaz Boustani, a study co-author and investigator at the Regenstrief Institute, discourages his patients from taking the drugs. But one bright spot in the study, was that the medications were linked with mild mental impairment, involving memory loss without functional disability, but not with Alzheimer's Disease, said Boustani.
Previous studies have shown negative short term effects on cognition and found a link between anticholinergics and delirium, a rapid change in a person’s mental state. This was one of the few that used longer term data.
It's possible that sleeplessness could be driving both the ingestion of the drugs and cognitive decine. But animal studies have found a direct effect of anticholinergics on neuron health, said Boustani.
The researchers next hope to conduct randomized controlled trials—the gold standard of research--and to focus on “whether anticholinergic-induced cognitive impairment may be reversible,” said Boustani, the founder and scientific director of the Indianapolis Discovery Network for Dementia.