Plasma beta-amyloid and duration of Alzheimer's disease in adults with Down syndrome.
OBJECTIVE
To investigate the relation of plasma levels of Abeta peptides (Abeta1-40 and Abeta1-42) and apolipoprotein E (APOE) genotype to dementia status, and the duration of Alzheimer's disease (AD) in adults with Down syndrome (DS).


METHODS
Adults with DS were recruited from community settings and followed up for a mean period of 6.7 years. Plasma levels Abeta1-40 and Abeta1-42 and APOE genotype were determined at the last visit.


RESULTS
There were 83 nondemented participants and 44 participants with prevalent AD. Overall, plasma levels of Abeta1-42, Abeta1-40 and the ratio Abeta1-42/Abeta1-40 did not differ significantly between the adults with DS. Among demented participants, the mean level of Abeta1-40 was significantly lower (157.0 vs. 195.3) and the ratio of Abeta1-42/Abeta1-40 was significantly higher (0.28 vs. 0.16) in those with more than 4 years duration of dementia than in those with 4 or fewer years' duration of dementia. This pattern was generally similar in those with and without an APOE epsilon4 allele.


CONCLUSIONS
There is an association between plasma Abeta peptide levels and the duration of AD in older persons with DS. The predictive and diagnostic roles of Abeta1-42 and Abeta1-40 measurements for AD, however, remain controversial. Change in Abeta peptide levels with onset of AD and with the duration of dementia may account for a lack of difference between prevalent cases and nondemented individuals and for variation in the predictive power of Abeta peptide levels.
Prasher
V P
VP
Monyhull Hospital, Liverpool John Moore University, c/o The Greenfields, Monyhull, Birmingham, UK. vprasher@compuserve.com
Sajith
S G
SG
Mehta
P
P
Zigman
W B
WB
Schupf
N
N
D000328:Adult; D000368:Aged; D000483:Alleles; D000544:Alzheimer Disease / Q000097:blood* / Q000175:diagnosis / Q000235:genetics; D016229:Amyloid beta-Peptides / Q000097:blood*; D053327:Apolipoprotein E4 / Q000235:genetics; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D003704:Dementia / Q000097:blood / Q000175:diagnosis; D004314:Down Syndrome / Q000097:blood* / Q000235:genetics; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood* / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011237:Predictive Value of Tests; D013997:Time Factors
D016229:Amyloid beta-Peptides; D053327:Apolipoprotein E4; D015415:Biomarkers; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)