Little evidence of reduced survival to adulthood of apoE ε4 homozygotes in Downʼs syndrome

IT has been proposed that homozygosity for the apolipoprotein E (apoE) ε4 allele decreases the probability of an individual with Downʼs syndrome (DS) surviving to adulthood. We performed a meta-analysis of 11 published DS series for which apoE genotype data were available. Seven ε4 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 ε4 allele frequencies in the individual series (p = 0.72). We conclude that there is little evidence that ε4/ε4 genotype frequency is substantially reduced in DS adults.