Meta-analysis of cognitive ability differences by apolipoprotein e genotype in young humans

The apolipoprotein (APOE) epsilon 4 allele has been proposed as an example of an antagonistic pleiotropy gene, conferring a beneficial effect on cognition in early life and a detrimental impact on cognition during later years. However, findings on the cognitive associations of the epsilon 4 allele in younger persons are mixed. This PRISMA conforming study aimed to investigate APOE genotype (e4/non-e4) associations across seven cognitive domains (intelligence/achievement, attention/working memory, executive functioning, memory, language, processing speed and visuospatial abilities) in younger humans using a meta-analytic approach. Of 689 records reviewed, 29 studies (34 data-points) were selected for the quantitative synthesis. Participants' ages ranged from 2-40. Results showed that young epsilon 4 carriers did not statistically differ from non-epsilon 4 carriers across any cognitive domains. Overall, findings do not provide compelling support for an antagonistic pleiotropic effect of the epsilon 4 allele across the lifespan.