The concept of mild cognitive impairment: relevance and limits in clinical practice.

Subtle cognitive impairments without dementia are common in the elderly population and numerous nosological entities have been proposed for their classification. The concept of mild cognitive impairment has become increasingly popular both in clinical practice and in research. It has been developed to describe a transitional zone between the cognitive changes of normal aging and early Alzheimer's disease or other forms of dementia. Its interest lies mainly in early identification of individuals who might be at risk of developing rapid cognitive decline. But the further one tends towards the early detection, the greater is the risk to lose in specificity. A number of other factors such as depression, metabolic or nutritional disorders, medication use, may cause cognitive dysfunctions and are reversible. The concept of mild cognitive impairment arouses a debate about its heterogeneity,limits, and relevance in clinical practice and research.