Researchers say that drugs commonly prescribed for allergies, hypertension, asthma, and cardiovascular might lead to cognitive impairment in older adults.
Drugs, such as diphenhydramine, which have an anticholinergic effect, are important medical therapies available by prescription and also are sold over the counter.
Older adults most commonly use drugs with anticholinergic effects as sleep aids.
"The public, physicians, and even the Food and Drug Administration, need to be made aware of the role of these common medications, and others with anticholinergic effects, in causing cognitive impairment," said senior study author Dr. Malaz Boustani, Indiana University School of Medicine associate professor of medicine.
"Patients should write down and tell their doctor which over-the-counter drugs they are taking.
"Doctors, who often think of these medications simply as antihistamines, antidepressants, antihypertensives, sleep aids or even itching remedies, need to recognize their systemic anticholinergic properties and the fact that they appear to impact brain health negatively," Boustani added.
The researchers analyzed 27 studies of the relationship of anticholinergic effect and brain function as well as investigating anecdotal information and found a strong link between anticholinergic effect and cognitive impairment in older adults.
"Many medications used for several common disease states have anticholinergic effects that are often unrecognized by prescribers" said Wishard Health Services pharmacist, Noll Campbell, Pharm.D., first author of the study, noting that these drugs are among the most frequently purchased over the counter products.
"In fact, 50 percent of the older adult population use a medication with some degree of anticholinergic effect each day," Campbell added.
"Our main message is that older adults and their physicians should have conversations about the benefits and harms of these drugs in relation to brain health," said Dr. Boustani.
The study appears in Journal of Clinical Interventions in Aging.