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Mild Cognitive Impairment Due to Alzheimer's in New Criteria

Mild cognitive impairment

It is difficult to know where to draw the line when deciding if someone has mild cognitive impairment (MCI), very mild Alzheimer’s disease, or mild Alzheimer’s dementia. An attempt to make the classification clearer is being considered, according to a study published Online First by Archives of Neurology, but what will a change mean to patients?

Would a classification change alter treatment?

Mild cognitive impairment is defined in a variety of ways that leaves room for interpretation. Generally, however, it is defined “by deficits in memory that do not significantly impact daily functioning,” as noted by the University of California San Francisco Memory and Aging Center.

Using this definition, problems with memory may be mild or minimal, and individuals are able to perform all their usual daily tasks and activities, such as driving, shopping, and attending social events, without any more assistance than they required in the past. Individuals with MCI do tend to have some difficulty with tasks that have many steps, however.

The new criteria for MCI, developed by a work group convened by the National Institute on Aging and the Alzheimer’s Association, allows features typically viewed as falling under the category of very mild or mild Alzheimer’s disease to be shuffled to the MCI category. For example, the criteria for MCI may including having “mild problems” while performing daily tasks such as cooking or needing assistance to complete tasks.

To evaluate how these new criteria would affect the diagnosis already given to 17,535 people with normal cognition, MCI, or Alzheimer’s disease dementia, the functional ratings of all the individuals were assessed based on the revised standards.

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Using the new criteria, 99.8% of patients currently with a diagnosis of very mild Alzheimer’s disease dementia and 92.7% of those diagnosed with mild Alzheimer’s dementia could be given a new diagnosis of mild cognitive impairment.

According to John C. Morris, MD, of Washington University School of Medicine in St. Louis and the study’s sole author, the new criteria are problematic.

“The elimination of the functional boundary between MCI and AD dementia means that their distinction will be based solely on the individual judgment of clinicians,” he noted, “resulting in nonstandard and ultimately arbitrary diagnostic approaches to MCI.”

Morris also pointed out, however, that “the revised criteria for MCI laudably recommend an etiologic diagnosis, ‘MCI due to AD,’ when the clinical judgment is that AD is responsible for the cognitive dysfunction.” In fact, he noted that it’s time to accept that “’MCI due to AD’ is more appropriately recognized” as the earliest stage of Alzheimer’s.

Will the new criteria change how patients are treated? Morris explained that it is already common for doctors to treat patients who have mild cognitive impairment with drugs approved for symptomatic Alzheimer’s disease.

Morris JC. Revised criteria for mild cognitive impairment may compromise the diagnosis of Alzheimer disease dementia. Archives of Neurology 2012 Feb 6 online. DOI:10.1001/archneurol.2011.3152

Image: Courtesy of Wikimedia Commons