Mild Cognitive Impairment Is Relevant

Abstract

Mild Cognitive Impairment Is Relevant Ronald C. Petersen (bio) Keywords aging, Alzheimer’s disease, dementia, mild cognitive impairment, pharmaceutical industry Graham and Ritchie (2006) have contributed a scholarly document that implores us to reexamine nosological categories and certain diagnostic outcomes. They have chosen mild cognitive impairment (MCI) as the target of their scrutiny and have raised several interesting issues. I would like to comment on their approach and suggest that MCI is a useful clinical entity that does serve a practical function and hopefully will lead to a better quality of life for aging persons. There are several clarifications concerning the construct of MCI that need to be emphasized. Graham and Ritchie have asserted that all persons with MCI eventually evolve to Alzheimer's disease (AD) and have claimed that this is the inevitable outcome of the disorder. Although it is true that many of the early studies on MCI focused on the amnestic subtype as a precursor to AD (Bennett et al. 2002; Ganguli, Dodge, Shen, and DeKosky 2004; Lopez et al. 2003; Petersen et al. 1999), subsequent work has expanded the construct to include prodromal forms of other disorders (Petersen 2004; Winblad et al. 2004). As such, the construct of MCI has become flexible in recent years to account for alternative types of intermediate cognitive impairment. The authors state that MCI addresses those individuals speculated to have an inevitable dementia. Certainly, we do not presume that dementia is inevitable in the aging process; rather, we posit that if certain criteria are fulfilled in persons who are aging, the likelihood of a person progressing to a certain type of dementia is quite high. As such, this is an important precondition about which to learn, because interventional strategies may be available. Graham and Ritchie argue that some cognitive changes with aging are "normal" and trying to classify these individuals as "abnormal" is performing a disservice to much of the aging population. We draw an important distinction between the cognitive changes of normal aging, as they are recognized to exist, and what we feel constitutes the pathologic changes of MCI. We believe that the abnormal cognitive function found in MCI has a high probability of progressing to a greater degree of cognitive dysfunction in a relatively short period of time and these behavioral changes are accompanied by pathologic brain changes that are manifested on magnetic resonance imaging scans, positron emission tomography scans, cerebrospinal fluid biomarkers, and autopsy studies (Hampel et al. 2004; Jack et al. 1999; Markesbery et al. [End Page 45] 2006; Petersen et al. 2006). This type of progression is in contradistinction to other individuals who are experiencing cognitive changes of normal aging. These individuals do not progress rapidly to greater degrees of impairment and autopsy studies reveal that their brains do not harbor the pathologic changes found in the MCI population (Knopman et al. 2003). The cognitive and behavioral changes accompanying persons with MCI are devastating and cannot be ascribed to "senility" or "He is just getting old." It is a mistake to imply that by labeling people with a condition such as MCI we are doing them a disservice. Most of these individuals are seeking medical attention for their perceived difficulties. Consequently, addressing these concerns and educating the individuals on the implications of their symptoms are important services. Although we may not have adequate therapies at present, this does not imply that we should ignore the symptoms. We cannot treat many conditions at present, yet we do not avoid the opportunity to characterize the condition and make a diagnosis. Even if this were part of the aging process, this does not mean that we should ignore the disability and refuse to treat it. Most individuals develop an inflexibility of their optical lenses as they age, yet corrective lenses of one type or another are believed to be extremely beneficial at alleviating this disability associated with the aging phenomenon. No one would argue that it is inappropriate to treat this condition because it is "just a part of aging." It should be noted that I have stressed the situation in which individuals are seeking medical attention for their cognitive concerns. It is quite a different situation if an...