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Neuropsychological characterization of cognitively-impaired-not-demented individuals Peters, Kevin Ross

Abstract

The focus of this dissertation was on Cognitively-Impaired-Not-Demented (CIND) individuals. CLND is a diagnostic label applied to individuals who present with cognitive impairment but do not meet formal criteria for dementia (Ebly, Hogan, & Parhad, 1995). The purpose of this research was to determine whether the cognitive heterogeneity of CIND could account for the prognostic heterogeneity of this condition. This dissertation is divided into two sections. The primary objective of the first section was to characterize the neuropsychological test performance of a large sample of clinic-referred CIND participants. Participants classified as Not-Cognitively-Impaired (NCI; n = 68) differed from CIND individuals (n = 205) on a number of demographic, clinical, and neuropsychological variables. Measures of learning and memory, visuoconstruction abilities, and cognitive flexibility provided the best discrimination between NCI and CIND participants. Clinical comparison data were generated for various demographically defined groups of CIND participants. The results supported the impression that CIND is a cognitively heterogeneous population. The primary objectives of the second section of this dissertation were, first, to determine whether subgroups of CIND individuals with distinct neuropsychological profiles exist in two independent samples, and second, to determine whether subgroup membership was related to diagnostic outcome over periods of 2 to 5 years. A series of cluster analyses was performed on ipsative factor z-scores derived from principal component analyses. Five subgroups were identified in the Base Sample (n = 461): Verbal Dysfunction, Verbal/Visuospatial Dysfunction, Memory/Verbal Dysfunction, Memory Dysfunction, and Visuospatial Dysfunction. This 5-cluster solution was replicated in an independent sample of CIND individuals (n = 166). The highest rates of conversion to dementia were observed in the Memory Dysfunction and Memory/Verbal Dysfunction subgroups. The Verbal Dysfunction subgroup was most likely to show improvement in cognitive status. The results suggest that CIND is a syndrome of conditions rather than a single population at risk for converting to dementia. This observation has implications for the diagnosis and treatment of CIND individuals. A deeper understanding of the cognitive heterogeneity of CIND will facilitate research to identify individuals who will and will not progress to dementia.

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