| Although the impact of the &egr;4 allele of the Apolipoprotein E gene (APOE-&egr;4) on cognitive functioning in adults has been widely studied, researchers have produced little information regarding the nature of this relationship in children. Broadly, the current studies aimed to explore APOE-related differences in cognitive functioning in early life. Study 1 explored the relationship between APOE genotype and educational attainment in a sample of elderly adults. Results indicated that even after accounting for Alzheimer's disease (AD) diagnostic status and gender, &egr;4-positive individuals attained fewer years of education relative to &egr;2-positive individuals. Studies 2, 3, 4 and 5 examined APOE-related differences in cognitive and achievement test performances in a sample of school-aged children. Scores on group achievement tests and on a measure of visuospatial functioning were compared between the genotype groups in Study 2, and results indicated significantly worse performance among &egr;2-positive children relative to &egr;3/3 homozygotes and &egr;4-positive children on a test of visuospatial functioning. Notably, an increased prevalence of left-handedness was also observed among &egr;2-positive individuals in both Studies 1 and 2. Study 3 examined achievement test data from multiple time points, and results indicated generally stable and equivalent performances over time across APOE genotype. Study 4, which is based on findings of atypical hemispheric asymmetries in normal-functioning young adults, investigated the extent to which the &egr;4 allele is associated with cognitive discrepancies in school-aged children. Findings indicated that APOE genotype is associated with cognitive asymmetry in early life, but that gender is a significant moderator of this association. Finally, Study 5, a preliminary study, explored whether APOE genotype interacts with a family history of AD to further impact the development of cognitive reserve. Remarkably, results showed a synergistic effect of APOE-&egr;4 status and family history of AD such that children with both risk factors showed the lowest test scores. Taken together, these studies suggest that APOE genotype is associated with early life brain and cognitive functioning. Results are discussed within the context of antagonistic pleiotropy, which suggests that APOE genotype may be associated with different effects at different developmental stages. |
