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Mild cognitive impairment (MCI) is an intermediate state between normal mental function and dementia. But it is possible to have a good qualify of life with MCI, and sometimes MCI doesn't progress to major neurocognitive disorder or even reverses itself.

What is your cognitive life expectancy? In the United States, once you reach the age of 65, your life expectancy is a little over 19 years — that is, you can be expected to die around the age of 84. But how well will your mind work?

The good news about growing older in the USA is that most seniors are mentally sharp. These figures are only averages, but at age 65, the average American can expect to spend another 14 years in good mental health, deal with minor cognitive impairment (problems with judgment, thinking skills, and memory that don't interfere with independent living) for four years, and to suffer dementia, on average, just a year-and-a-half. Even the “the majority of cognitively impaired years are happy ones, not unhappy ones,” says Anthony Bardo, an assistant professor of sociology at the University of Kentucky at Lexington and a specialist in qualify of life in older people diagnosed with cognitive impairment.

What is this kind of "dementia" that allows you to continue to enjoy your life? In the United States, there is a definition of an intermediate state between normal mental functioning and life-limiting dementia called mild cognitive impairment. 

Differences between minor and major cognitive impairment

The DSM-5, a manual for psychiatric and neuropsychiatric diagnosis used by physicians in the United States, has a definition for "minor neurocognitive disorder" that encompasses a broad spectrum of declining mental abilities that still allow independent living. If you were to "grade on a curve," someone with a minor neurocognitive disorder would score in the the third to sixteenth percentile on an intelligence test (one to two standard deviations below the mean).  A minor neurocognitive disorder might correspond roughly to an IQ between 70 and 85. Someone with a major neurocognitive disorder would score in the third percentile or lower, more impaired than 97 percent or more of the general population. A major neurocognitive disorder might correspond to an IQ of 55 to 70.

There are no hard and fast cutoff points for either major or minor neurocognitive disorders. For a neurocognitive disorder to be "minor," several other considerations apply:

  • Minor and major cognitive impairment differ by degrees of disability. Someone who has minor cognitive impairment can still carry out all their activities of daily life. They may not be as fast as they used to be. They may have a tendency to get taken in by scammers. But they function independently. In major cognitive impairment, varying degrees of assistance are needed for basic daily activities.
  • But minor and major cognitive impairment may be different stages of the same disease. Alzheimer's, Parkinson's, traumatic brain injury, and vascular diseases of the brain can cause either minor or major cognitive symptoms.

Different diagnostic standards for mild and major cognitive impairment

The definition of mild cognitive impairment takes into account the fact that some cases of mild cognitive impairment are reversible. An example of this is the cognitive impairment that follows traumatic brain injury. If you get hit in the head, and you lose consciousness, or you are confused immediately after the event, or you suffer memory loss for a short time, you can be classified with mild cognitive impairment. It is not necessary to run a brain scan to confirm this diagnosis. In traumatic brain injury, the diagnosis of mild cognitive impairment can be made on the basis of behavior alone.

Why wouldn't it be necessary to do an MRI or a CT scan to make the diagnosis in this situation? Most people who have a single traumatic brain injury recover their cognitive faculties. They may be at measurably greater risk for developing dementia over the long run, but they are not usually permanently disabled by a single brain injury.

For a traumatic brain injury to be diagnosed as causing major cognitive impairment, there are different standards of diagnosis. For a "major" impairment, damage to the brain must be confirmed by MRI, CT, and/or PET scans. There must be objective testing that finds that the injured person is performing on a level two standard deviations below the mean, that is, in the third percentile or lower. And there must be a reason to believe that the consequences of the injury are permanent.

There are also differences in mild and major cognitive impairment in Alzheimer's. In minor cognitive impairment, there has to be loss of just one area of cognitive functioning, and independent activities of daily life must remain intact. In major cognitive impairment, there must be loss of memory plus one other area of cognitive functioning, and there must be a loss of abilities to live independently. These losses must be progressive, and there must not be any other explanation for them.

Medication may help people who have mild cognitive impairment avoid major cognitive impairment.  It may be possible to delay the progression of cognitive impairment in some cases. Aricept (donepezil) slows down the progression of Alzheimer's. Lisinopril (the blood pressure medication) slows down the progression of some kinds of vascular dementia. Ask your doctor if these medications are appropriate for you.

Mild cognitive impairment and good quality of life

Surveys of older Americans have found that seniors with no cognitive impairment report being happy 90 percent of the time. Seniors with mild cognitive impairment report being happy 85 percent of the time. People with cognitive impairment can go through tough times, but that is also true of anyone at any point in life Most older people will be disabled by major cognitive impairment for only a short part of their lives. Even when there is mild cognitive impairment, a good quality of life is still possible.

  • Petersen RC. Conceptual overview. Petersen RC. Mild Cognitive Impairment: Aging to Alzheimer's Disease. 1-14. New York, NY: Oxford University Press, Inc
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  • Alzheimer's Disease Neuroimaging Initiative (ADNI). Baseline MRI predictors of conversion from MCI to probable AD in the ADNI cohort. Current Alzheimer Research. 2009 Aug. 6(4):347-61. Simon SS, Yokomizo JE, Bottino CM. Cognitive intervention in amnestic Mild Cognitive Impairment: A systematic review. Neurosci Biobehav Rev. 2012 Feb 1. 36(4):1163-1178.
  • Photo courtesy of SteadyHealth

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