Effects of education mediated by brain size on regional brain volume in adults.

Abstract

Brain structure and function change with age. Both educational attainments, a proxy for cognitive reserve, and intracranial volume (ICV), a proxy for brain reserve, could contribute to resilience against degenerative change in the brain with aging. Whether the effect of educational attainment on regional brain volume in adults is mediated by ICV is yet unclear. We aimed to investigate the direct and indirect effects (mediated through ICV) of education in early life on regional brain volume in later life. We investigated the association between ICV and education level and regional brain volume in adults using magnetic resonance imaging scans of 1,731 individuals from multicenter studies. The mediation effect of ICV was analyzed to determine the association between educational attainment at an earlier age and regional brain volume in adults. Our results showed that the effect of education on regional brain volume was significantly mediated by ICV in both men and women. The indirect (mediated via ICV) effect of education on brain volume amounted to 75% of the total effect in the hippocampus (p<0.001) and 100% in the frontal and insular gray matter (p<0.001). Our study demonstrated that the association between educational attainment in early life and regional brain volume in later life was largely mediated by ICV. Attention should be given to the effect of educational attainment and ICV on regional brain size in adults as a measurable resilience effect in brain aging.