Affiliations: [a] Department of Psychiatry, Loma Linda University, Redlands, CA, USA | [b] Department of Statistics, University of California, Riverside, CA, USA | [c] Department of Medicine, Loma Linda University Health Care, Loma Linda, CA, USA | [d] Health Research Consulting Group, Loma Linda University, Loma Linda, CA, USA | [e] Neurosurgery Center for Research, Training, and Education, Loma Linda University, Loma Linda, CA, USA
Correspondence:
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Correspondence to: Wolff M. Kirsch, Neurosurgery Center for Research, Training, and Education, Loma Linda University, 11234 Anderson St., Room A537, Loma Linda, CA, USA. Tel.: +(909) 558 7070; Fax: +(909) 558 0472; E-mail: wkirsch@llu.edu.
Abstract: The majority of mild cognitive impairment (MCI) studies use baseline and one follow-up measurement to determine the clinical course of the disorder. This report of MCI clinical course is based on the a statistical evaluation of multiple neurocognitive tests over a 60 month period in elderly normal and MCI cohorts. The data includes serial informant-based measures (Clinical Dementia Rating [CDR]) and a comprehensive battery of neuropsychological tests analyzed by two different regression methods. Twenty-nine elderly participants entered the study as neurocognitively normal; 26 remained normal, 2 progressed to MCI, and 1 progressed to dementia. Eighty-three participants entered the study as multiple domain MCI cases; 10 became normal, 46 remained MCI, and 27 progressed to dementia. Three of the 27 demented died with full necropsies performed (one case was progressive supranuclear palsy and two confirmed Alzheimer's disease with severe cerebral amyloid angiopathy (CAA)). Without serial measures, 1 in 8 MCI could be misclassified as “stable MCI” despite reverting to normal. The stable MCI cohorts did not benefit from practice effects though the normal subjects did. Applying Classification and Regression Tree (CART) analysis enabled prediction of the endpoint status of participants from baseline values with 78.6% accuracy. The fluctuating cognitive status of the multiple domain MCI cases implies a remitting pathologic process with elements of recovery consistent with a progressive microvasculopathy such as CAA.
Keywords: Informant-based evaluation, mild cognitive impairment, misdiagnosis, neuropsychological testing, practice effects, serial neurocognitive evaluations
