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Current Gerontology and Geriatrics Research
Volume 2013 (2013), Article ID 495793, 10 pages
http://dx.doi.org/10.1155/2013/495793
Research Article

Intraindividual Variability in Domain-Specific Cognition and Risk of Mild Cognitive Impairment and Dementia

1Department of Social Sciences and Health Policy, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC, USA
2Wake Forest University, Winston-Salem, NC, USA
3National Institute on Aging, Baltimore, MD, USA
4Family and Community Medicine, University of Nevada School of Medicine, Reno, NV, USA

Received 7 August 2013; Revised 31 October 2013; Accepted 31 October 2013

Academic Editor: Arnold B. Mitnitski

Copyright © 2013 Leslie Vaughan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Intraindividual variability among cognitive domains may predict dementia independently of interindividual differences in cognition. A multidomain cognitive battery was administered to 2305 older adult women (mean age 74 years) enrolled in an ancillary study of the Women’s Health Initiative. Women were evaluated annually for probable dementia and mild cognitive impairment (MCI) for an average of 5.3 years using a standardized protocol. Proportional hazards regression showed that lower baseline domain-specific cognitive scores significantly predicted MCI ( ), probable dementia ( ), and MCI or probable dementia combined ( ) and that verbal and figural memory predicted each outcome independently of all other cognitive domains. The baseline intraindividual standard deviation across test scores (IAV Cognitive Domains) significantly predicted probable dementia and this effect was attenuated by interindividual differences in verbal episodic memory. Slope increases in IAV Cognitive Domains across measurement occasions (IAV Time) explained additional risk for MCI and MCI or probable dementia, beyond that accounted for by interindividual differences in multiple cognitive measures, but risk for probable dementia was attenuated by mean decreases in verbal episodic memory slope. These findings demonstrate that within-person variability across cognitive domains both at baseline and longitudinally independently accounts for risk of cognitive impairment and dementia in support of the predictive utility of within-person variability.