Apo E genotypes and risk of dementia in Down syndrome.

The relationship between apo E genotypes and risk of dementia in Down syndrome is not clear. Accordingly, we have analysed this locus in 20 demented and 25 nondemented individuals with Down syndrome and combined these data with other studies in a meta-analysis. The meta-analysis revealed an estimated odds ratio for dementia of 2.74 (95% CI 1.34-5.58) (P =.0004) for apo epsilon4 carriers compared with apo epsilon3/epsilon3, similar to that observed in late-onset Alzheimer's disease. An additional parallel with late-onset Alzheimer's disease was shown by the apo epsilon2 allele, which was associated with decreased dementia risk in Down syndrome (odds ratio for apo epsilon2/epsilon2 + epsilon2/epsilon3 = 0.37 (95% CI 0.14-0. 96)). Thus, apo E genotypes are associated with similar risk effects in Down syndrome dementia and late-onset Alzheimer's disease.