Elevated plasma amyloid beta-peptide 1-42 and onset of dementia in adults with Down syndrome

We compared levels of plasma amyloid p-peptides A beta1-42 and A beta1-40 i n 108 demented and nondemented adults with Down syndrome (DS) and 64 adults from the general population. A beta1-42 and A beta1-40 levels were signifi cantly higher in adults with DS than in controls (P = 0.0001). Compared to nondemented adults with DS, A beta1-42 levels in demented adults with DS we re selectively increased by 26% (28.2 pg/ml vs. 22.4 pg/ml, P = 0.004). In addition, mean plasma levels of A beta1-42 were 22% higher in DS cases with the apolipoprotein epsilon4 allele than in DS subjects without an epsilon4 allele 125.9 pgi mi vs. 21.2 pg/ml, P = 0.01), while mean plasma levels of A beta1-40 did not vary by APOE genotype. These results support the hypoth esis that A beta1-42 plays an important role in the pathogenesis of dementi a associated with DS, as it does in Alzheimer's disease, and that variation s in plasma levels may be related to disease progression. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.