Affiliations: [a] Department of Psychiatry, The University of Texas Health Science Center, San Antonio, TX, USA | [b] Department of Medicine, The University of Texas Health Science Center, San Antonio, TX, USA | [c] Department of Family and Community Medicine, The University of Texas Health Science Center, San Antonio, TX, USA | [d] South Texas Veterans' Health System Audie L. Murphy Division GRECC, San Antonio, TX, USA | [e] Department of Internal Medicine and Institute for Aging and Alzheimer's Disease Research, University of North Texas Health Sciences Center, Fort Worth, TX, USA
Correspondence:
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Correspondence to: Donald R. Royall, M.D., Department of Psychiatry, The University of Texas Health Sciences Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229-3900, USA. Tel.: +1 210 567 1255; Fax: +1 210 567 1269; E-mail: royall@uthscsa.edu.
Abstract: The cognitive correlates of functional status are essential to dementia case-finding. Nevertheless, cognitive performance is a generally weak predictor of functional outcomes. We have employed structural equation models to explicitly distinguish functional status, and therefore “dementia-relevant” variance in cognitive task performance (i.e., δ) from the variance that is unrelated to a dementing process (i.e., g'). Together, g' + δ encompass Spearman's g. Although δ represents only a small fraction of the total variance in cognitive task performance, it is more strongly associated with dementia status than is g'. In this study, we validate δ in a well characterized Alzheimer's disease cohort, the Texas Alzheimer's Research and Care Consortium. Our approach results in “error free” continuous variables. This suggests that δ can serve as a dementia specific endophenotype. As a result, future studies may be able to associate δ with inflammatory and genetic biomarkers.
Keywords: Aging, cognition, dementia, functional status, g
