Reduced size of right hippocampus in 39- to 80-year-old normal subjects carrying the apolipoprotein E epsilon 4 allele

Hippocampal size on magnetic resonance imaging was compared between normal subjects with the apolipoprotein E (ape E) epsilon 4 allele (epsilon 4/4, epsilon 4/3, and epsilon 4/2) and those without the epsilon 4 allele (epsilon 3/3, epsilon 3/2, and epsilon 2/2) in the age range of 39-80 years. The Mini-Mental State Examination (MMSE) scores did not differ between the two groups. The right hippocampal area and its ratio to hemisphere area and intracranial cavity area were significantly smaller in epsilon 4 carriers than non-carriers, whereas hemisphere area did not differ between the two groups, These results suggest that as early as their forties, apo E epsilon 4 allele carriers have a markedly smaller right hippocampus with no apparent cognitive impairment, which may have some significance in the high prevalence of the epsilon 4 allele in Alzheimer's disease as well as other conditions that cause dementia. (C) 1997 Elsevier Science Ireland Ltd.