Do Cognitive Enhancing Drugs Improve Memory and Thinking in Older Adults?

Getting older? Forgetting things and having fuzzy thinking? Or perhaps you have a parent or other loved one whose ability to remember or concentrate isn’t as good as it used to be. This is called mild cognitive impairment or MCI. About 1 in 5 adults who are 71 years old or older have MCI,[1] which means they have more trouble thinking and remembering than most other people their age, but their condition is not severe enough to be considered dementia or Alzheimer’s.[2] MCI doesn’t, for instance, interfere with a person’s ability to care for himself or carry out daily activities.

Close to 60% of people with MCI develop it as a result of medical conditions such as stroke or diseases that affect veins and arteries, depression, or conditions involving the brain and nervous system. The good news is that only about one-third are in the very early stages of Alzheimer’s, the most common form of dementia. The bad news is that anywhere from 3% to 17% of people with MCI find that their condition worsens, turning into dementia within a year,[3],[4],[5] and that increases to one-third of the patients after two years.[6] People with dementia have problems remembering, thinking, and reasoning. They may not be in control of their emotions, making it difficult for them to sustain relationships. They may be agitated or have hallucinations.

Screening Older People for Cognitive Impairment

Should all older adults be screened for cognitive impairment? A 2013 study published in the Annals of Internal Medicine found that although good, simple screening tests exist, diagnosing people in the early stages of cognitive impairment has no proven benefit.[7] Why not? Because there are no treatments, exercises, or other strategies that are proven to really work. The only benefit to knowing about cognitive impairment early on is it allows patients, family members, and caregivers to plan better for the future.

What About “Cognitive-Enhancing Drug”?

There are “cognitive-enhancing drugs,” but unfortunately research shows that they don’t help with mild cognitive impairment. Cognitive-enhancers won’t prevent Alzheimer’s or dementia but they very likely will make you feel nauseous and have diarrhea and headaches.

People with dementia are often treated with one of two types of cognitive enhancers: 1) a cholinesterase inhibitor, such as donepezil, rivastigmine, and galantamine (brand names Aricept, Exelon, and Razadyne); or 2) memantine (brand name Namenda). Since these drugs improve some symptoms of dementia and allow people with moderate to severe Alzheimer’s to function better, doctors began prescribing them to patients with only mild cognitive impairment in hopes that it would help them, too. Wishful thinking is not science, however, and finally researchers studied the impact of these drugs on MCI and published their results in September 2013 in CMAJ, the Journal of the Canadian Medical Association.

With a grant from the Canadian Institutes of Health, researchers combined data from 8 comparable studies of patients, ages 66 to 73 years old, and analyzed them. Similar to two well-respected reviews published in 2006 and 2012,[8],[9] the Canadian researchers found that none of the cognitive enhancers mentioned above slowed patients’ development of dementia compared to placebo. While results differed somewhat depending on the drug, the test used to evaluate patients, and the length of the study, those patients who appeared to benefit from cognitive enhancers did so only for a short window of time. After that window, the patients on cognitive enhancers went back to performing the same as the patients on placebo. Unfortunately, the unpleasant side-effects were more long-lasting:  patients who took cognitive enhancers were significantly more likely to suffer nausea, headaches, vomiting, and even a slower heartbeat (brachycardia) for 2 to 4 years after beginning their use. The side effects were not life-threatening, but there is no point in giving drugs that have such unpleasant side effects if they don’t have meaningful benefits.

The Bottom Line:

Cognitive enhancing drugs may help some patients with moderate to severe Alzheimer’s or dementia to function better, but they don’t help older people with mild cognitive impairment. Taking these pills only ensures that they will feel sick to their stomach while losing their cognitive skills.

All NCHR articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff. 
1.  Brenda L. Plassman, Kenneth M. Langa, Gwenith G. Fisher, Steven G. Heeringa, David R. Weir, Mary Beth Ofstedal, James R. Burke, Michael D. Hurd, Guy G. Potter, Willard L. Rodgers, David C. Steffens, John J. McArdle, Robert J. Willis, Robert B. Wallace; Prevalence of Cognitive Impairment without Dementia in the United States. Annals of Internal Medicine. 2008 Mar;148(6):427-434.
3. Farias ST, Mungas d, Reed BR, et al. Progression of mild cognitive impairment to dementia in clinic- vs community-based cohorts. ArchNeurol 2009;66:1151-7.
4. Busse A, Angermeyer MC, Riedel-Heller SG. Progression of mild cognitive impairment to dementia: a challenge to current thinking. Br J Psychiatry 2006;189:399-404.
5. Landau SM, Harvey d, Madison CM, et al. Comparing predictors of conversion and decline in mild cognitive impairment. Neurology 2010;75:230-8.
6. Ritchie K. Mild cognitive impairment: an epidemiological perspective. Dialogues Clin Neurosci 2004;6:401-8.
8. Russ TC, Morling JR. Cholinesterase inhibitors for mild cognitive impairment. Cochrane Database System Rev 2012;9:CD009132.
Birks J, Flicker L, Donepezil for mild cognitive impairment. Cochrane Database Syst Rev 2006;(3):CD006104