Apolipoprotein E and Cognitive Performance: A Meta-Analysis.

The epsilon4 allele of the apolipoprotein E (APOE) gene is a known risk factor for Alzheimer's disease and may also affect cognitive performance in normal aging. Evidence of the presence and magnitude of epsilon4-related cognitive deficits was examined with a meta-analysis of the available literature. Thirty-eight studies were included, and cognitive performance was collapsed into 8 domains. Results indicated significant APOE-epsilon4 group differences for global cognitive functioning, episodic memory, and executive functioning, in favor of non-epsilon4 carriers. In addition, older age and APOE-epsilon4 heterozygosity was associated with smaller epsilon4-related impairments. The meta-analysis results suggest that APOE-epsilon4 genotype does affect cognitive performance in healthy aging, although the influence is relatively small and specific to certain domains of cognitive performance.