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

Objectives 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.
Method 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. Results 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 (?=0.387,
p=0.002), and education was associated with reduced decline in Speed
(?=0.237, p=0.039). Discussion 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.