Effects of brain maintenance and cognitive reserve on age-related decline in three cognitive abilities

<p><strong>Objectives </strong></p> <p>Age-related cognitive changes can be influenced by both brain maintenance (BM), which refers to the relative absence over time of changes in neural resources or neuropathologic changes, and cognitive reserve (CR), which encompasses brain processes that allow for better-than-expected behavioral performance given the degree of life-course related brain changes. This study evaluated the effects of age, BM, and CR on longitudinal changes over two visits, 5 years apart, in three cognitive abilities that capture most of age-related variability.</p> <p><strong>Method </strong></p> <p>Participants included 254 healthy adults aged 20–80 years at recruitment. Potential BM was estimated using whole brain cortical thickness and white matter mean diffusivity at both visits. Education and IQ (estimated with AMNART) were tested as moderating factors for cognitive changes in the three cognitive abilities.</p> <p><strong> Results </strong></p> <p>Consistent with BM—after accounting for age, sex, and baseline performance—individual differences in the preservation of mean diffusivity and cortical thickness were independently associated with relative preservation in the three abilities. Consistent with CR—after accounting for age, sex, baseline performance, and structural brain changes—higher IQ, but not education, was associated with reduced 5-year decline in Reasoning (𝛽=0.387, p=0.002), and education was associated with reduced decline in Speed (𝛽=0.237, p=0.039). <strong> </strong></p> <p><strong>Discussion</strong></p> <p>These results demonstrate that both CR and BM can moderate cognitive changes in healthy aging and that the two mechanisms can make differential contributions to preserved cognition.</p>