A new study warns consumers to beware: a number of common medications, such as Tylenol, Benadryl and Dramamine, may cause cognitive impairment and even increase the risk of death.

Medications with anticholinergic activity are frequently taken among the elderly adult population and include both over-the-counter drugs as well as prescription medicine.  Anticholinergics affect the brain by blocking acetylcholine, a neurotransmitter.

Most anticholinergic drugs contain diphenhydramine, which is sold over-the-counter under popular brand names, including Benadryl, Dramamine, Excedrin PM, Nytol, Sominex, Tylenol PM and Unisom. Prescription anticholinergic drugs include Paxil, Detrol, Demerol and Elavil.

Researchers studied the impact of these drugs on 13,000 men and women aged 65 or older over a period of two years.  They found that, even controlling for a variety of other factors, taking anticholinergic medications was linked to cognitive impairment and death in this population.

Generally, elderly people take the anticholinergics for various ailments and diseases, such as sleep disorders, incontinence, hypertension and congestive heart failure, according to researchers.

"Physicians should review with older patients all the over-the-counter and prescription drugs they are taking to determine exposure," said study co-author Malaz Boustani, M.D., Regenstrief Institute investigator, Indiana University School of Medicine associate professor of medicine, and research scientist with the IU Center for Aging Research

The study was published in the Journal of the American Geriatrics Society.