OBJECTIVE: Royall and colleagues identified a latent dementia phenotype, "δ", reflecting the "cognitive correlates of functional status." We sought to cross-validate and extend these findings in a large clinical case series of adults with and without dementia.
METHOD: A confirmatory factor analysis (CFA) model for δ was fit to National Alzheimer's Coordinating Center data (n = 26,068). Factor scores derived from δ were compared with the Clinical Dementia Rating Sum of Boxes (CDR-SB) and to clinically diagnosed dementia. A longitudinal parallel-process growth model compared changes in δ with changes in CDR-SB over 6 annual evaluations.
RESULTS: The CFA model fit well; CFI = 0.971, RMSEA = 0.070. Factor scores derived from δ discriminated between demented and nondemented participants with an area under the curve of .96. The growth model also fit well, CFI = 0.969, RMSEA = 0.032.
CONCLUSIONS: The δ construct represents a novel approach to measuring dementia-related changes and has potential to improve cognitive assessment of neurodegenerative diseases.