Moderating effect of cognitive reserve on the association between grey matter atrophy and memory varies with age in older adults

Abstract

Background: Educational attainment and verbal intelligence, which indirectly reflect an individual's cognitive reserve (CR), is suggested to buffer the effect of late-life brain degradation on cognitive performance outcome. We aimed to explore how the relationship between whole grey matter volume (GMV) and episodic memory function is altered by CR proxy as well as age in healthy older adults. Methods: Elderly Verbal Learning Test (EVLT) and structural magnetic resonance imaging were administered to 110 community-residing older adults. Moderated moderation model tested whether the association between whole GMV and episodic memory was moderated by both CR and chronological age. Results: The results showed that the moderating effect of CR on Immediate Recall, Short-delay Recall, and Recognition scores of EVLT differed across age groups. The elderly with higher CR showed steeper GMV effect on EVLT at the Age-Younger condition, while such moderating effect was reversed in the Age-Older condition, suggesting an alleviated brain atrophy effect in higher CR elderly. Conclusion: These findings suggest that although higher CR elderly may exhibit earlier GMV-related memory decline, the buffering effect of CR on the cognitive decline due to brain atrophy would become more evident in old-old elderly people who are likely to have accumulated more neuropathological changes. This study underscores chronological age as an important moderating factor in examining the moderating role of CR in late-life memory function.

Verbal intelligence is a more robust cross-sectional measure of cognitive reserve than level of education in healthy older adults

“…Robust moderation effects of CR proxies on the association between brain structure-as measured by GM volume, hippocampal volume, or mean cortical thicknessand cognition were not identified here. This lack of evidence is in line with previously reported non-significant moderation effects on the relationship between episodic memory and GM volume [59] and right hippocampal volume [102] but conflicts with previous evidence of significant moderation effects reported for CR proxies in similar brain-cognition models [46,124,135]. However, the evidence for moderation is largely inconsistent as highlighted by the finding of moderation effects reported on 1 measure, but not on 2 other measures, of episodic memory within the same study [135] and even findings of a positive moderation effect, which contradicts the CR hypothesis, on the relationship between left hippocampal volume and episodic memory [102].…”

Verbal intelligence is a more robust cross-sectional measure of cognitive reserve than level of education in healthy older adults

“…This is a novel nding as the most robust composite -occupational complexity and verbal intelligence -has never (to the best of our knowledge) been used previously as a CR proxy, likely due to the predominant use of education both as an individual proxy and in composites. The next most robust composite of education and verbal intelligence has been widely used (42,43,45,46,59,78,111) and our results support a previous positive association between this composite and episodic memory, controlling for GM volume (59). A speculative explanation for the greater robustness of occupational complexity and verbal intelligence as a composite may be that occupational complexity and verbal intelligence are less strongly correlated with each other than educational attainment and verbal intelligence (see Fig.…”

“…The composite of verbal intelligence and education moderated the relationship of subcortical grey matter (GM) volume and cortical thickness with uid reasoning but not memory or processing speed and attention (46). This composite was also associated with memory controlling for GM volume (59) and global cognition controlling for a composite AD-biomarker (45). Although other composites have been associated with cognition (50), there is very little empirical evidence regarding their effects within complete CR models.…”

Verbal Intelligence, Not Level of Education, Robustly Assesses Cognitive Reserve

“…This is a novel nding as the most robust composite -occupational complexity and verbal intelligence -has never (to the best of our knowledge) been used previously as a CR proxy, likely due to the predominant use of education both as an individual proxy and in composites. The next most robust composite of education and verbal intelligence has been widely used (60)(61)(62)81,82,107,108) and our results support a previous positive association between this composite and episodic memory, controlling for GM volume (61). A speculative explanation for the greater robustness of occupational complexity and verbal intelligence as a composite may be that occupational complexity and verbal intelligence are less strongly correlated with each other than educational attainment and verbal intelligence (see Fig.…”

“…The composite of verbal intelligence and education has been reported to moderate the relationship of subcortical grey matter (GM) volume and cortical thickness with uid reasoning but not memory or processing speed and attention (60). This composite has also been associated with memory controlling for GM volume (61) and global cognition controlling for a composite AD-biomarker (62). Aside from the composite of verbal intelligence and education, there is very little empirical evidence regarding the effects of different CR composites within complete models.…”