Common medication to treat insomnia, anxiety, itching or allergies can have a negative impact on memory or concentration in the elderly, according to Dr. Cara Tannenbaum, Research Chair at the Institut universitaire de gériatrie de Montréal (IUGM, Montreal Geriatric University Institute) and Associate Professor of Medicine and Pharmacy at the University of Montreal (UdeM). Up to ninety percent of people over the age of 65 take at least one prescription medication. Eighteen percent of people in this age group complain of memory problems and are found to have mild cognitive deficits. Research suggests there may be a link between the two.

Dr. Tannenbaum recently led a team of international researchers to investigate which medications are most likely to affect amnestic (memory) or non-amnestic (attention, concentration, performance) brain functions. After analyzing the results from 162 experiments on medications with potential to bind to cholinergic, histamine, GABAergic or opioid receptors in the brain, Dr. Tannenbaum concluded that the episodic use of several medications can cause amnestic or non-amnestic deficits. This potential cause is often overlooked in persons who are otherwise in good health.

The 68 trials on benzodiazepines (which are often used to treat anxiety and insomnia) that were analyzed showed that these drugs consistently lead to impairments in memory and concentration, with a clear dose-response relationship. The 12 tests on antihistamines and the 15 tests on tricyclic antidepressants showed deficits in attention and information processing. Dr. Tannenbaum's findings support the recommendation issued in the Revised Beers Criteria published last spring 2012 by the American Geriatrics Society that all sleeping pills, 1st generation antihistamines and tricyclic antidepressants should be avoided at all costs in seniors.

Dr. Tannenbaum believes in the importance of communicating this knowledge to patients: "Seniors can play an important role in reducing the risks associated with these medications. Patients need this information so that they are more comfortable talking to their doctors and pharmacists about safer pharmacological or non-pharmacological treatment options," she explained. She also points out that each case must be addressed on an individual basis: "Despite the known risks, it may be better for some patients to continue their medication instead of having to live with intolerable symptoms. Each individual has a right to make an informed choice based on preference and a thorough understanding of the effects the medications may have on their memory and function."

Research summary MEDLINE and EMBASE were searched for randomized, double-blind, placebo-controlled trials of adults without underlying central nervous system disorders who underwent detailed neuropsychological testing prior to and after oral administration of drugs affecting cholinergic, histaminergic, GABAergic or opioid receptor pathways. Seventy-eight studies were identified, reporting 162 trials testing medication from the four targeted drug classes. Two investigators independently appraised study quality and extracted relevant data on the occurrence of amnestic, non-amnestic or combined cognitive deficits induced by each drug class. Only trials using validated neuropsychological tests were included. Quality of the evidence for each drug class was assessed based on consistency of results across trials and the presence of a dose-response gradient. This research was conducted in collaboration with researchers at the University of Sydney, the University of Calgary and the University of Iowa College of Public Health.