Little evidence of reduced survival to adulthood of apoE epsilon 4 homozygotes in Down's syndrome

IT has been proposed that homozygosity for the apolipoprotein E (apoE) epsilon 4 allele decreases the probability of an individual with Down's syndrome (DS) surviving to adulthood. We performed a meta-analysis of 11 published DS series for which apoE genotype data were available. Seven epsilon 4 homozygotes out of a total of 538 DS adults have been reported in the literature. This number is not significantly different from that expected based on the epsilon 4 allele frequencies in the individual series (p = 0.72). We conclude that there is little evidence that epsilon 4/epsilon 4 genotype frequency is substantially reduced in DS adults.