Indianapolis, IN—Pharmacists might want to caution older adults about using OTC products such as nighttime cold medicines because of increased risk of cognitive impairment, according to a new study.

While previous research has linked anticholinergic (AC) drugs to cognitive impairment and increased risk of dementia, the new study, published online recently by JAMA Neurology, used cognitive scores, mean fludeoxyglucose F 18 standardized uptake value ratio, and brain atrophy measures from structural magnetic resonance imaging to measure the effects of the medications.

Indiana University School of Medicine researchers found reduced brain sizes among study participants using drugs with anticholinergic effect as well as lower metabolism and cognitive decline. The medications block acetylcholine, a nervous system neurotransmitter, according to the study.

“These findings provide us with a much better understanding of how this class of drugs may act upon the brain in ways that might raise the risk of cognitive impairment and dementia,” said first author Shannon Risacher, PhD, assistant professor of radiology and imaging sciences. “Given all the research evidence, physicians might want to consider alternatives to anticholinergic medications if available when working with their older patients.”

The article notes that drugs with anticholinergic effects are sold OTC and by prescription to aid sleep as well as for many chronic diseases including hypertension, cardiovascular disease, and chronic obstructive pulmonary disease.

The study involved 451 participants drawn from the Alzheimer’s disease Neuroimaging Initiative and the Indiana Memory and Aging Study; 60 of them were taking at least one medication with medium or high anticholinergic activity.

Researchers used positron emission tests measuring brain metabolism and MRI scans to identify possible physical and physiological changes that could be associated with the reported effects. They also assessed the results of memory and other cognitive tests.

Results from the cognitive tests indicated that patients taking anticholinergic drugs performed worse than older adults not using the drugs on short-term memory and some tests of executive function. The research also demonstrated lower levels of glucose metabolism, a biomarker for brain activity, in both the overall brain and in the hippocampus, a region of the brain associated with memory and which has been identified as affected early by Alzheimer’s disease.

Significant links also were found between brain structure revealed by the MRI scans and anticholinergic drug use. Participants using anticholinergic drugs had reduced brain volume and larger ventricles, the cavities inside the brain, the study points out.

“These findings might give us clues to the biological basis for the cognitive problems associated with anticholinergic drugs, but additional studies are needed if we are to truly understand the mechanisms involved,” Risacher said in an Indiana University press release.

The researchers urge that the “use of AC medication among older adults should likely be discouraged if alternative therapies are available.”

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