Mild cognitive impairment - Clinical characterization and outcome

Background: Subjects with a mild cognitive impairment (MCI) have a memory i mpairment beyond that expected for age and education yet are not demented. These subjects are becoming the focus of many prediction studies and early intervention trials. Objective: To characterize clinically subjects with MCI cross-sectionally a nd longitudinally. Design: A prospective, longitudinal inception cohort. Setting: General community clinic. Participants: A sample of 76 consecutively evaluated subjects with MCI were compared with 234 healthy control subjects and 106 patients with mild Alzh eimer disease (AD), all from a community setting as part of the Mayo Clinic Alzheimer's Disease Centered/Alzheimer's Disease Patient Registry, Rochest er, Minn. Main Outcome Measures: The 3 groups of individuals were compared on demogra phic factors and measures of cognitive function including the Mini-Mental S tate Examination, Wechsler Adult Intelligence Scale-Revised, Wechsler Memor y Scale-Revised, Dementia Rating Scale, Free and Cued Selective Reminding T est, and Auditory Verbal Learning Test. Clinical classifications of dementi a and AD were determined according to the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition and the National Institute of N eurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria, respectively. Results: The primary distinction between control subjects and subjects with MCI was in the area of memory, while other cognitive functions were compar able. However, when the subjects with MCI were compared with the patients w ith very mild AD, memory performance was similar, but patients with AD were more impaired in other cognitive domains as well. Longitudinal performance demonstrated that the subjects with MCI declined at a rate greater than th at of the controls but less rapidly than the patients with mild AD. Conclusions: Patients who meet the criteria for MCI can be differentiated f rom healthy control subjects and those with very mild AD. They appear to co nstitute a clinical entity that can be characterized for treatment interven tions.