What is mild cognitive impairment? Variations in definitions and evolution of nondemented persons with cognitive impairment.

Numerous studies have endeavoured to explore the nature of cognitive impairment in nondemented elderly persons. Comparison of this literature is hampered by huge variations in criteria and methodology. Despite these limitations, there are repeated reports that nondemented persons with cognitive impairment have a higher chance of progressing to dementia. Evidence also indicates higher mortality in cognitively impaired persons but there is also a chance of improvement in cognition over time. The current paper provides an overview of the various concepts and criteria proposed for cognitive impairment in nondemented persons, discusses some of the problems with current research in this field, and presents some of the findings concerning the evolution of cognitive impairment in relation to dementia, mortality and cognitive improvement.