APOLIPOPROTEIN EPSILON-4 ALLELE IN SWEDISH TWINS AND SIBLINGS WITH ALZHEIMER-DISEASE

Allelic frequencies of apolipoprotein epsilon 4 were compared in 13 di zygotic twin pairs and 13 sibling pairs in which at least one member h as Alzheimer disease (AD). Among discordant pairs of twins and sibling s, frequencies were significantly greater in affected than intact part ners. There was no significant difference in allelic frequencies betwe en twins with a positive family history and twins with a negative fami ly history. The epsilon 4 allele was more common in the sibling sample selected for family aggregation of AD than the twin sample. Several l ines of evidence indicate that while the epsilon 4 allele appears to b e one risk factor for AD, other etiological factors must be considered as well.