Cortical thickness is associated with different apolipoprotein E genotypes in healthy elderly adults

Previous studies have consistently suggested that the ɛ4 allele of apolipoprotein E (APOE) gene is a major risk factor for Alzheimer's disease (AD). However, whether the ɛ2 allele, a possible protective factor for AD, will express its protective effect in terms of cortical thickness in healthy elderly carriers is unclear. The goal of this study is to clarify the effects of APOE genotypes on cortical thickness in nondemented elderly subjects. We used 164 healthy, cognitively normal, elderly subjects, who were grouped into ɛ2 carriers, ɛ3 homozygotes, and ɛ4 carriers respectively. The APOE ɛ2 carriers had a significant thicker (corrected p < 0.05) cortical thickness in the superior temporal cortex compared with the ɛ3 homozygotes. In addition to this area, the APOE ɛ2 carriers had a significantly thicker region in the dorsolateral prefrontal cortex (corrected p < 0.05) than did the ɛ4 carriers. These findings suggest that the different alleles of the APOE gene have distinct neuroanatomic effects in elderly healthy subjects and may play specific roles in the development of AD.