Apolipoprotein E ϵ4 allele and hippocampal volume in twins with normal cognition

We examined the relation of APOE-ϵ4, hippocampal volume, and cognitive performance in ten pairs of cognitively normal twins who had a mean age of 62.5 years (SD = 7.8). There were no significant differences in neuropsychological measures of the groups categorized by the presence of an ϵ4 allele. However, the mean normalized right and left hippocampal volumes were smaller in the ϵ4 group compared to the group without ϵ4. Combined with prior reports, these findings suggest that ϵ4 is associated with differences in brain morphology that may be evident when no symptoms of dementia are present.