MCI Not Improved by Cognitive Enhancers

Cognitive enhancers—drugs taken to enhance concentration, memory, alertness and moods—do not improve cognition or function in people with mild cognitive impairment (MCI) in the long term, according to a new study by researchers at St Michael's Hospital.

In fact, patients on these medications experienced significantly more nausea, diarrhea, vomiting and headaches, according to the study published in the Canadian Medical Association Journal.

"Our findings do not support the use of cognitive enhancers for mild cognitive impairment," wrote Andrea Tricco, PhD, and Sharon Straus, MD, who are both scientists in the hospital's Li Ka Shing Knowledge Institute. Straus is also a geriatrician at the hospital.

Between 3% and 42% of people are diagnosed with MCI each year, about 4.6 million people worldwide. Each year about 3% to 17% of people with MCI will develop dementia, such as Alzheimer's disease.

It has been hypothesized that cognitive enhancers may delay the onset of dementia. Families and patients are increasingly requesting these drugs even though their efficacy for patients with MCI has not been established.

Tricco and Straus conducted a review of existing evidence to understand the efficacy and safety of cognitive enhancers. They looked at eight randomized trials that compared one of four cognitive enhancers (donepezil, rivastigmine, galantamine, or memantine) to a placebo among patients diagnosed with MCI.

While they found short-term benefits to using these drugs on one cognition scale, there were no long-term effects after about a year and a half. No other benefits were observed on the second cognition scale or on function, behaviour, and mortality. As well, patients on these medications experienced significantly more nausea, diarrhea, vomiting, and headaches. One study also found a higher risk of bradycardia (slow heartbeat) among patients who received galantamine.

"Our results do not support the use of cognitive enhancers for patients with mild cognitive impairment," the authors wrote. "These agents were not associated with any benefit and led to an increase in harms. Patients and their families should consider this information when requesting these medications. Similarly, health care decision-makers may not wish to approve the use of these medications for mild cognitive impairment, because these drugs might not be effective and are likely associated with harm."