Common medications such as Advil, Tylenol, Benadryl, Sominex and many others may increase the risk of cognitive decline and Alzheimer’s disease, according to a study published this fall in the journal Neurology.

Known as anticholinergics, this broad class of drugs includes over-the-counter and prescription medications used to treat a wide range of conditions —  everything from allergies, sleep issues and mood disorders to high blood pressure, bladder problems, chronic obstructive pulmonary disease, asthma and Parkinson’s.

Anticholinergics work by blocking the neurotransmitter acetylcholine, which is responsible for learning and memory as well as for muscle contractions. More than 600 medications have some degree of anticholinergic activity. 

Researchers from the University of California San Diego School of Medicine tracked the cognitive function of 688 older individuals, all of whom had normal memory and cognitive function at the start of the study, over a ten-year period. Participants had an average age of 74 and were equally divided by sex. Nearly one-third were taking anticholinergics, on average 4.7 anticholinergics per person among those using them. Researchers administered cognitive tests annually to participants and checked for genetic risk factors for Alzheimer’s as well as biomarkers (biological signs) indicating the presence of the disease. 

Who’s at greatest risk for Alzheimer’s disease?

Anticholinergics are metabolized by the liver and normally have short-term effects on the body. However, older adults have a slower ability to metabolize medications. This puts them at an increased risk of adverse drug reactions.

Researchers also found that genetics and biological factors can increase the risk of cognitive impairment. Among anticholinergic drug users, those with a higher genetic risk for Alzheimer’s disease were 2.5 times more likely to experience cognitive impairments, while those with biomarkers for Alzheimer’s disease were four times more likely to experience cognitive impairments. 

Study authors noted that 57% of the participants were taking twice the recommended dosage of anticholinergics, while 18% were taking four times the amount. 

In addition to the relatively small sample size, one of the limitations of the study was that participants were predominantly white and well-educated. 

Safety recommendations for anticholinergic drug users

It’s important to talk to your health care professional about the risks and benefits of anticholinergic medications based on your personal medical situation and history, as well as to have them regularly review all your medications for potential interactions and overall safety. 

As well, many pharmacists will review medication lists for free, offering their recommendations on dose adjustments or the need to discontinue medications if there are safety concerns.