Classification and epidemiology of MCI.

Mild cognitive impairment (MCI) is an intermediate stage in the trajectory from normal cognition to dementia. Despite controversies about the classification of MCI, recent published criteria for MCI allow better comparison of the prevalence, incidence, and outcomes of MCI. Subjects with MCI have a high rate of progression to dementia over a relatively short period. In this review, we present an overview of the classification of MCI, estimates of the incidence and prevalence of MCI, risk factors for MCI, and the outcomes following an MCI diagnosis.