Biological Age and 12-Year Cognitive Change in Older Adults: Findings from the Victoria Longitudinal Study

BACKGROUND: Although recent cross-sectional findings indicate that markers of biological age (BA) mediate chronological age (CA) differences in cognitive performance, little is known about their influence on actual cognitive changes. OBJECTIVE: The purpose of this investigation is to examine CA and BA as predictors of 12-year cognitive change in a longitudinal sample of older adults. METHODS: Data from the Victoria Longitudinal Study (VLS) were examined for 125 adults between 67 and 95 years of age. Biomarkers, including visual and auditory acuity, grip strength, peak expiratory flow, blood pressure, and body mass index, were submitted to a factor analysis and a composite BA variable was computed based on factor loadings. Intraindividual change across 5 waves of measurement (3-year intervals) was examined as a function of CA and BA for 5 cognitive domains: verbal processing speed, working memory, reasoning, episodic memory, and semantic memory. RESULTS: The latent structure of biomarkers was consistent with previous investigations of functional age and a common factor view of biological aging. Results of hierarchical linear modeling showed that BA predicted actual cognitive change (decline) independent of CA. CONCLUSIONS: As a predictor of cognitive performance in late life, CA is a proxy for biological and environmental influences. We have shown that biological influences are independent predictors of actual cognitive change in older adults. This supports the view that cognitive decline is not due to aging per se, but rather is likely due to causal factors that operate along the age continuum.