Mild cognitive impairment
What is it?
Mild cognitive impairment is a transition stage between the cognitive decline of normal aging and the more serious problems caused by Alzheimer's disease.
The disorder can affect many areas of thought and action — such as language, attention, reasoning, judgment, reading and writing. However, the most common variety of mild cognitive impairment causes memory problems.
Mild cognitive impairment affects about 20 percent of the population over 70. Many people with mild cognitive impairment eventually develop Alzheimer's disease, although some remain stable and others even return to normal.
The forgetfulness of normal aging is minor. You misplace your car keys or lose your car in the parking garage. Perhaps you can't remember the name of a former co-worker when you meet unexpectedly at the grocery store. This is nothing to worry about.
But red flags should go up if you start forgetting things you typically remember, such as doctor's appointments or your weekly pinochle game. This happens to everyone now and then, but if a pattern develops, it could be a symptom of mild cognitive impairment.
Commonly used criteria for a diagnosis of mild cognitive impairment are:
- Deficient memory, preferably confirmed by another person
- Essentially normal judgment, perception and reasoning skills
- Largely normal activities of daily living
- Reduced performance on cognitive tests, compared with other people of similar age and educational background
People with mild cognitive impairment may also experience:
Mild cognitive impairment often causes the same types of brain changes seen in Alzheimer's disease or other forms of dementia. The difference is in the extent of these changes, which is limited in mild cognitive impairment. These changes may include:
- Plaques, which are abnormal clumps of a protein called beta-amyloid
- Tangles, which are abnormal clumps of a protein called tau
- Shrinkage of the hippocampus, an area of the brain important for memory
- Lewy bodies, which are abnormal clumps of a protein that's associated with Parkinson's disease
- A specific change in a gene, called apolipoprotein E (APOE), which has been linked to Alzheimer's disease
- High blood pressure
- Low levels of physical, social and mental activity
- Fewer years of education
People with mild cognitive impairment are three times more likely to develop Alzheimer's or other dementias than are those without such impairment. In fact, about half the people with mild cognitive impairment will progress to Alzheimer's disease within five years.
There is no specific test to confirm a diagnosis of mild cognitive impairment. Instead, your doctor will try to rule out other potential causes for your symptoms. Tests may include the following.
As part of your physical exam, your doctor may also check for signs of Parkinson's disease, strokes, tumors or other medical conditions that can impair memory as well as physical function. The neurological exam may test:
- Eye movements
- Sense of touch
Mental status exam
A short form of this type of test can be done in less than 10 minutes in your doctor's office. You may be asked to:
- Name today's date and your location
- Copy a design, such as intersecting pentagons
- Follow a three-stage command
- Remember a list of three words
- Follow a written direction
- Count backwards by sevens
- Draw a clock
Longer forms of neuropsychological testing can take several hours. Your results are then compared with those of people from a similar age and education level. This can help distinguish normal from abnormal cognitive aging, and may help identify patterns in cognitive functions that provide clues to the underlying condition.
Simple blood tests can rule out physical problems that can affect memory, such as vitamin B-12 deficiency or an underactive thyroid gland.
Your doctor may order an MRI or CT scan to check for evidence of stroke or bleeding, and to rule out the possibility of a tumour.