Education mitigates age-related decline in N-Acetylaspartate levels

Abstract

Background: Greater educational attainment is associated with better neurocognitive health in older adults and is thought to reflect a measure of cognitive reserve. In vivo neuroimaging tools have begun to identify the brain systems and networks potentially responsible for reserve.

Methods: We examined the relationship between education, a commonly used proxy for cognitive reserve, and N-acetylaspartate (NAA) in neurologically healthy older adults (N=135; mean age=66 years). Using single voxel MR spectroscopy, we predicted that higher levels of education would moderate an age-related decline in NAA in the frontal cortex.

Results: After controlling for the variance associated with cardiorespiratory fitness, sex, annual income, and creatine levels, there were no significant main effects of education (B=0.016, P=0.787) or age (B=-0.058, P=0.204) on NAA levels. However, consistent with our predictions, there was a significant education X age interaction such that more years of education offset an age-related decline in NAA (B=0.025, P=0.031). When examining working memory via the backwards digit span task, longer span length was associated with greater education (P<0.01) and showed a trend with greater NAA concentrations (P<0.06); however, there was no age X education interaction on digit span performance nor a significant moderated mediation effect between age, education, and NAA on digit span performance.

Conclusions: Taken together, these results suggest that higher levels of education may attenuate an age-related reduction in neuronal viability in the frontal cortex.

Keywords: Aging; brain reserve; cognitive reserve; education; fitness.

Figure 1

Location of the single voxel in the magnetic resonance spectroscopy sequence. The voxel contained portions of the inferior frontal gyrus, middle frontal gyrus, insula, and anterior basal ganglia.

Figure 2

For graphical purposes, the sample was divided into groups, fewer years of education (<17 years; solid line) and higher amounts of education (>17 years; dotted line), based on the Johnson–Neyman calculated threshold of significance. The figure shows that older age is associated with lower NAA levels, but only in the lower education group. This effect was significant after controlling for sex, fitness level, Cr, and income.