Definition of Mild Cognitive Impairment — By Mayo Clinic staff
Mild cognitive impairment (MCI) is an intermediate stage between the expected cognitive decline of normal aging and the more pronounced decline of dementia. It involves problems with memory, language, thinking and judgment that are greater than typical age-related changes. If you have mild cognitive impairment, you may be aware that your memory or mental function has “slipped.” And your family and close friends may also notice a change. But generally these changes aren’t severe enough to interfere with your day-to-day life and usual activities.
Mild cognitive impairment increases your risk of later developing dementia, including Alzheimer’s disease, especially when your main difficulty is with memory. But some people with mild cognitive impairment never get worse, and a few eventually get better.
Your brain changes as you grow older just like the rest of your body. Many people notice gradually increasing forgetfulness as they age. It may take longer to think of a word or to recall a person’s name.
But consistent or increasing concern about your mental performance may suggest MCI. Cognitive issues may go beyond what’s expected and indicate possible MCI if you experience any or all of the following:
- You forget things more often.
- You forget important events such as appointments or social engagements.
- You lose your train of thought or the thread of conversations, books or movies.
- You feel increasingly overwhelmed by making decisions, planning steps to accomplish a task or interpreting instructions.
- You start to have trouble finding your way around familiar environments.
- You become more impulsive or show increasingly poor judgment.
- Your family and friends notice any of these changes.
If you have MCI, you may also experience:
- Irritability and aggression
There’s no single cause of MCI, just as there’s no single outcome for the disorder. Symptoms of MCI may remain stable for years, progress to Alzheimer’s disease or another type of dementia, or improve over time.
Current evidence indicates that MCI often, but not always, causes a lesser degree of the same types of brain changes seen in Alzheimer’s disease or other forms of dementia. Some of these changes have been identified in autopsy studies of people with MCI. These changes include:
- Plaques and tangles, which are microscopic protein clumps characteristic of Alzheimer’s disease
- Lewy bodies, which are microscopic clumps of another protein associated with Parkinson’s disease, dementia with Lewy bodies and some cases of Alzheimer’s disease
- Small strokes or reduced blood flow through brain blood vessels
Brain-imaging studies show that the following changes are often associated with MCI:
- Shrinkage of the hippocampus, a brain region important for memory
- Plaques (abnormal clumps of beta-amyloid protein) throughout the brain
- Enlargement of the brain’s fluid-filled spaces (ventricles)
- Reduced use of glucose, the sugar that’s the primary source of energy for cells, in key brain regions
The strongest risk factors for MCI are:
- Increasing age
- Having a specific form of a gene known as APOE-e4, also linked to Alzheimer’s disease — though having the gene doesn’t guarantee that you’ll experience cognitive decline
Other medical conditions and lifestyle factors have been linked to an increased risk of cognitive change, but the evidence for these risk factors is less clear-cut. These risk factors include:
- Current smoking
- High blood pressure
- Elevated cholesterol
- Lack of physical exercise
- Infrequent participation in mentally or socially stimulating activities
People with MCI have a significantly increased risk — but not a certainty — of developing Alzheimer’s disease or another type of dementia. Overall, about 1 to 2 percent of older adults develop dementia every year. Among older adults with MCI, studies suggest that 6 to 15 percent may develop dementia every year.
Another Definition — Mild Cognitive Impairment
Mild cognitive impairment (MCI) a condition in which a person has problems with memory, language, or another mental function severe enough to be noticeable to other people and to show up on tests, but not serious enough to interfere with daily life.
Because the problems do not interfere with daily activities, the person does not meet criteria for being diagnosed with dementia. The best-studied type of MCI involves a memory problem and is called “amnestic MCI.”
- Research has shown that individuals with MCI have an increased risk of developing Alzheimer’s disease over the next few years, especially when their main problem is memory.
- Not everyone diagnosed with MCI goes on to develop Alzheimer’s.
- There is currently no treatment for MCI approved by the FDA.
- Results of a large, federally funded trial showed that 10 milligrams of donepezil (Aricept) daily can reduce the risk of progressing from amnestic MCI to Alzheimer’s disease for about a year, but the benefit disappears within three years. The trial also showed that 2,000 international units of vitamin E daily do not reduce the risk of progressing.
- The study authors say the results were not strong enough to support a clear recommendation to treat amnestic MCI with donepezil, but it might be reasonable for patients and their physicians to talk about the possible benefits and risks of treatment on an individual basis
- Two other studies have tested galantamine (Razadyne) as a treatment for MCI. These studies found no benefit, but the data showed an increased number of deaths in participants taking galantamine compared with those receiving the placebo.