Drugs to treat Alzheimer's disease don't help patients with mild cognitive impairment and are linked to greater risk of harm, a Canadian review concludes.

People with mild cognitive impairment show symptoms of memory problems that are not severe enough to be considered dementia or to interfere with day-to-day functioning. Each year, three to 17 per cent of people with mild cognitive impairment deteriorate to dementia, research suggests.

It was hoped that "cognitive enhancers" used to treat dementia might delay progression to dementia.

Dr. Sharon Straus of the department of geriatric medicine at the University of Toronto and her team reviewed clinical trials and reports on the effects of four cognitive enhancers.

"Cognitive enhancers did not improve cognition or function among patients with mild cognitive impairment and were associated with a greater risk of gastrointestinal harms," the reviewers concluded in Monday's issue of the Canadian Medical Association Journal.

"Our findings do not support the use of cognitive enhancers for mild cognitive impairment."

The medications act on different neurotransmitters in the brain, such as acetylcholine. The drugs are:

Donepezil (Aricept).

Rivastigmine (Exelon).

Galantamine (Reminyl).

Memantine (Ebixa).

Drugs not approved for pre-Alzheimer's use

Straus says patients and their families are increasingly requesting the medications, and she suspects that some of the off-label prescriptions are for mild cognitive impairment, a use that Health Canada hasn't officially approved.

The trials were done between 1999 and 2007 in North America, Europe, New Zealand, Australia, South America, Israel and Turkey. All the studies compared cognitive enhancers with placebos. The average age of the patients ranged from 66 to 73.

The meta-analysis showed patients taking the medications experienced more nausea, diarrhea, vomiting and headaches than those taking placebos. One study found a higher incidence of bradycardia, or slow heart rate, among patients taking galantamine.

In 2004, there were 900,000 prescriptions filled for the medications, said study co-author Andrea Tricco at St. Michael's Hospital in Toronto.

"It does lead us to believe that … perhaps, people are taking these medications that shouldn't be," Tricco said.

The authors suggested longer-term trials to ensure accuracy of results beyond 84 weeks of followup.

The Canadian Consensus Conferences on the Diagnosis and Treatment of Dementia have also not been recommending acetylcholinesterase inhibitors for mild cognitive impairment, said Dr. Paul Verhoeff, a psychiatrist in the Behavioural Neurology Memory Disorders Clinic at Baycrest Health Sciences in Toronto, who was not involved in the research.

For people with mild cognitive impairment, Verhoeff suggested strategies to compensate for memory loss, such as:

Associating names with a name you already know.

Remembering images of scenes.

Keeping an appointment book in the same place at all times or using reminders on digital devices.

"The difficulty, it's almost an oxymoron, is that people have memory problems, and you have to teach them new strategies to compensate for these memory problems," Verhoeff said.

Baycrest has a program, which is going national, to help patients retain the strategies and to educate loved ones, since their support is also extremely important, Verhoeff said.

He stressed the importance of paying attention to the common risk factors among heart disease, stroke and Alzheimer's, such as high blood pressure and cholesterol levels, diabetes and excess weight.

The review was funded by the Drug Safety and Effectiveness Network at the Canadian Institutes of Health Research.

