Introduction: It is well established that the Apolipoprotein E (APOE) ε4 allele is associated with cognitive impairment and Alzheimer's disease in old age. By contrast, several studies have demonstrated cognitive benefits in young ε4 carriers. It is therefore possible that the ε4 allele exhibits a pleiotropic association with cognition across the life span where ε4-related benefits in youth reverse to become risk factors for cognitive impairment and dementia in later life. To date, though, there has been no broad quantitative review of work assessing APOE-cognition associations in children, adolescents and young adults.
Method: Based on 20 studies investigating cognitive performance in ε4-carrying young persons and their non-ε4 counterparts, a meta-analytic study was conducted to examine APOE ε4-related differences in cognitive performance. Additionally, we assessed whether the level of executive demands affected the strength of associations between the ε4 allele and cognitive measures.
Results: In all analyses, estimated APOE ε4-related population effect sizes did not reliably differ from zero. Furthermore, the level of executive demands of the task did not affect this finding.
Conclusion: We found no APOE ε4-related cognitive benefits in young adults, adolescents and children, and findings were not moderated by the level of executive demands in a cognitive task. Given the current empirical evidence therefore, suggestions that APOE ε4 exhibits a pleiotropic association with cognition across the life span should be treated with caution.