Mild Cognitive Impairment
Mild Cognitive Impairment* (MCI) is a syndrome of cognitive decline greater than expected for an individual’s age and education level, but it does not meet the diagnostic criteria for dementia. The cognitive changes (deficits) in memory, language, visuospatial ability, or executive function are severe enough to be noticeable to other people and to show up on tests of cognitive functioning. However, these changes are not severe enough to significantly interfere with the person’s everyday social and occupational functioning. This is what distinguishes this cognitive disorder from dementia. MCI is currently receiving a great deal of clinical and research attention. One important goal of this research is to identify and treat individuals with MCI before they develop dementia and if possible delay or prevent progression to dementia. Mild Cognitive Impairment increases a person’s risk of later developing dementia, including of the Alzheimer’s type, especially when the main difficulty is with memory. In many cases, MCI is actually the prodromal stage of dementia and the transitional phase between normal age-related cognitive decline and early dementia. However, some people with mild cognitive impairment do not go on to develop dementia. MCI, like dementia, is not a normal part of aging.
Mild Cognitive Impairment (MCI) consists of:
- Consistent mild to moderate cognitive impairment in one or more domain (usually memory) that is beyond what would be expected for that person’s age. It is more severe than normal age-related cognitive decline. Neuropsychological testing can determine if a person’s memory complaints, for example, are due to normal aging or due to a genuine deficit and disorder.
- The deficit in a particular domain such as memory is 1.5 standard deviations below the mean for the person’s age and education.
- Other cognitive deficits may or may not be present.
- The person does not meet the diagnostic criteria for dementia. The symptoms may interfere with everyday activities, but do not significantly affect social or occupational functioning.
Short-term memory impairment actually means the person has difficulty learning new information. Amnestic MCI and dementia are defined as memory disorders. Old memories that were laid down and stored many years ago, when learning was intact, are preserved. Even though new information cannot be learned, the old memories and old habits remain until the dementia becomes more advanced. With severe memory impairment, as with more advanced dementia, new information is not learned. This new information is rapidly lost because it does not get stored.
Dr. Ron Peterson and his colleagues at the Mayo Clinic have developed the core diagnostic criteria for MCI. It is as follows:
- A memory complaint, preferably corroborated by an informant.
- Objective memory impairment for the person’s age (ideally confirmed by neuropsychological testing).
- Normal general cognitive function.
- Normal activities of daily functioning.
- No dementia.
Further research delineated the following: The cognitive deficits may have a mild impact on performance of complex ADLs and still not meet the diagnostic criteria for dementia because the impact is not significant.
How might short-term memory impairment be expressed in someone who is retired and has been living in the same house and neighborhood for many years? What signs and symptoms would family members notice? These might include some of the following:
- Asking the same questions repeatedly
- Telling the same stories repeatedly
- Forgetting recent conversations
- Frequently misplacing belongings
- Not remembering names of familiar people
- Forgetting that something is cooking on the stove
- Forgetting to pay bills or paying bills more than once
- Forgetting appointments or to take medications
- Stop doing things like reading novels or playing Bridge
- Difficulty learning a new device or appliance (cell phone, TV remote, etc.)
Subtypes of MCI
Amnestic MCI (there is a memory deficit)
- Single domain type means memory function is the only cognitive domain affected.
- Multiple domain type means memory and one or more other cognitive domains are affected, such as language or executive function.
Non-Amnestic MCI (there is no memory deficit)
- Single domain type is when the one domain affected is language or visuospatial or some other domain other than memory.
- Multiple domain type is when the person shows deficits in more than one domain and none of these are memory function.
Approximately 70% of patients with Amnestic MCI will eventually progress to dementia. Clearly, MCI is a risk factor for developing dementia. Amnestic MCI is a risk factor for developing Alzheimer’s dementia.
Vascular Cognitive Impairment is when the person has mild cognitive deficits that are believed to be the result of a stroke or vascular disease. However, the deficit or deficits are not severe enough to significantly impact the person’s everyday social and occupational functioning and thus does not meet the full diagnostic criteria for Vascular Dementia.
*called Mild Neurocognitive Disorder in DSM 5
Agronin, Marc E. Alzheimer Disease and Other Dementias (3rd Edition), Lippincott Williams & Wilkins, USA, 2014.
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th Edition. APA: Washington DC, 1994.
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th Edition. APA: Washington DC, 2013.
Budson, Andrew E. MD and Solomon, Paul R. PhD, Memory Loss: A Practical Guide for Clinicians Elsevier 2011.
Budson AE, Solomon PR. New criteria for Alzheimer disease and mild cognitive impairment: implications for the practicing clinician. Neurologist. 2012 Nov;18(6):356-63.
Golomb J, Kluger A, Ferris SH. Mild cognitive impairment: historical development and summary of research. Dialogues Clin Neurosci. 2004 Dec;6(4):351-67.
Loring, David W. (Editor) INS Dictionary of Neuropsychology and Clinical Neurosciences
2nd Edition Oxford University Press, New York, N.Y. 2015
Perry, Robert; McKeith, Ian, & Perry, Elaine, (Editors) Dementia with Lewy Bodies: Clinical, Pathological, and Treatment Issues Cambridge University Press, England, 1996.
Peterson, Ronald C. (Ed) Mild Cognitive Impairment: Aging to Alzheimer’s Disease Oxford University Press, USA, 2003.
Peterson, RC. Mild cognitive impairment as a diagnostic entity. J Intern Med.2004 Sep:256(3):183-94
Peterson R, Negash S. CNS Spectr. Vol 13, No 1. 2008.
Reisberg B, Ferris SH, Kluger A, Franssen E, Wegiel J, de Leon MJ. Mild cognitive impairment (MCI): a historical perspective. Int Psychogeriatr. 2008 Feb;20(1):18-31.