Onset of dementia is associated with apolipoprotein E epsilon4 in Down's syndrome

We examined the influence of apolipoprotein E (apoE) genotype on risk of dementia in 82 adults with Down's syndrome (DS). Compared with those with an apoE 3/3 genotype, the group of adults with DS with apoE 2/4, 3/4, and 4/4 genotypes were 5 times more likely to become demented (RR = 4.7; 95% CI = 1.2, 17.9). We hypothesize that the increased risk of dementia may be mediated by exacerbation of beta-amyloid deposition.