Mild Cognitive Impairment: Current Research and Clinical Implications

Ronald C. Petersen, Ph.D., M.D.


Semin Neurol. 2007;27(1) 

In This Article

Abstract and Introduction


Mild cognitive impairment refers to the transitional state between the cognitive changes of normal aging and the fully developed clinical features of dementia. This topic has received a great deal of attention in the literature in recent years and is being proposed for clinical applications as well. Clinical guidelines, including the original memory-focused criteria and the more recent broadly defined set of criteria, will be presented. The clinical outcome of individuals with mild cognitive impairment will be discussed and several explanations for variability in the literature will be considered. Predictors of progression, including genetic, neuroimaging, biomarker, and clinical characteristics, will be presented, as will the controversies regarding the underlying neuropathology of mild cognitive impairment. The recently completed mild cognitive impairment clinical trials will be discussed and the lessons learned from them translated into recommendations for future investigations. Finally, the clinical utility of mild cognitive impairment, its incorporation into clinical practice, and directions for future research will be proposed.


With the aging of America, increasing attention is being paid to the quality of life as one ages. A major factor in determining quality of life involves one's cognitive capacity. As such, a great deal of research is focusing on disease prevention, particularly with respect to degenerative diseases of the brain. Most people fear the development of a neurodegenerative disorder as much as they fear cancer and cardiovascular disease.

Alzheimer's disease (AD), Parkinson's disease, dementia with Lewy bodies, and vascular dementia are important clinical conditions that have a major impact on aging persons. There are several research studies currently underway aimed at delaying the onset of these disorders through disease-modifying therapies.[1] A complementary approach to this line of research involves the desire to make the diagnosis of an incipient degenerative or vascular disorder at its earliest juncture. Mild cognitive impairment is being proposed as a condition of intermediate symptomology between the cognitive changes of aging and fully developed symptoms of dementia such as those seen in AD. The rationale for the study of mild cognitive impairment is derived from the assumption that the sooner one intervenes in a degenerative process, the more likely the damage done to the central nervous system can be prevented. Hence the construct has been developed to represent a transitional stage between the cognitive changes of aging and very early dementia as shown in Fig. 1.

Figure 1.


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