Cognitive reserve as residual variance in cognitive performance: Latent dimensionality, correlates, and dementia prediction.

Abstract

Cognitive reserve (CR) is typically operationalized as episodic memory residualized on brain health indices. The dimensionality of more generalized models of CR has rarely been examined. In a sample of N = 113 dementia-free older adults (ages 62-86 years at MRI scan; 58.4% women), the domain-specific representation of general cognition (COG) before vs. after residualization on brain indices (brain volume loss, cerebral blood flow, white matter hyperintensities) was compared (i.e., COG vs. CR). COG and CR were assessed by 15 tasks spanning five domains: processing speed, verbal memory, visuospatial memory, fluid reasoning, and vocabulary. Measurement invariance and item-construct representation were tested in a series of structural factor analyses. COG and CR were then examined in relation to 22 risk and protective factors and dementia status at time of death. Item-factor loadings differed such that CR more strongly emphasized fluid reasoning. More years of education, higher occupational class, more hobbies/interests, and fewer difficulties with personal mobility similarly predicted better COG and CR. Only the sub-domain of visuospatial memory (both before and after residualization) was associated with conversion to dementia by end-of-life (r = -.30; p = .01). Results provide tentative support for the role of fluid reasoning (intelligence) as a potential compensatory factor for age- and/or neuropathology-related reductions in processing speed and memory. Intellectually stimulating work, efforts to preserve personal mobility, and a diversity of hobbies and interests may attenuate age- and/or pathology-related reductions in cognitive functioning prior to dementia onset.