@article {1025, title = {Plasma amyloid levels and the risk of AD in normal subjects in the Cardiovascular Health Study.}, journal = {Neurology}, volume = {70}, year = {2008}, month = {2008 May 06}, pages = {1664-71}, abstract = {

OBJECTIVES: To examine the association between incident Alzheimer disease (AD), and plasma A beta 1-40 and A beta 1-42 levels in normal and mild cognitive impairment (MCI) subjects in a subgroup of participants of the Cardiovascular Health Study Cognition Study.

METHODS: We determined the plasma A beta 1-40 and A beta 1-42 levels of 274 nondemented subjects (232 normals and 42 with MCI) in 1998-1999 and repeated the measurements in 2002-2003. The mean age of the subjects at baseline was 79.3 +/- 3.6 years. We examined the association between A beta levels and incident AD over the ensuing 4.5 years, controlling for age, cystatin C level (marker of glomerular function), apolipoprotein E-4 allele, Modified-Mini-Mental State Examination scores, and MRI-identified infarcts.

RESULTS: In an unadjusted prospective model in normal subjects, both A beta 1-40 and A beta 1-42 levels in 1998-1999 were associated with incident AD (n = 55) in 2002-2003 (longitudinal analysis). In the fully adjusted multivariate model, neither A beta 1-42 nor A beta 1-40 nor their ratio was associated with incident AD. However, adjustment had a very small effect on point estimates for A beta 1-42, from an odds ratio (OR) of 1.61 (p = 0.007) in the unadjusted model to an OR of 1.46 (p = 0.08) in the fully adjusted model. In 2002-2003 (cross-sectional analysis), only the unadjusted models showed that both peptides were associated with AD.

CONCLUSIONS: Plasma A beta levels are affected by age and by systemic and CNS vascular risk factors. After controlling for these conditions, A beta-40 and A beta 1-42 are weak predictors of conversion to Alzheimer disease (AD) in normal subjects and are only weakly associated with AD in cross-sectional analysis. Consequently, plasma levels of A beta do not seem to be useful biomarkers for AD.

}, keywords = {Age Factors, Aged, Aged, 80 and over, Alzheimer Disease, Amyloid beta-Peptides, Apolipoprotein E4, Biomarkers, Brain, Cerebrovascular Disorders, Comorbidity, Cross-Sectional Studies, Cystatin C, Cystatins, Female, Humans, Incidence, Longitudinal Studies, Magnetic Resonance Imaging, Male, Models, Statistical, Neuropsychological Tests, Peptide Fragments, Predictive Value of Tests, Prospective Studies, Reference Values, Risk Factors}, issn = {1526-632X}, doi = {10.1212/01.wnl.0000306696.82017.66}, author = {Lopez, O L and Kuller, L H and Mehta, P D and Becker, J T and Gach, H M and Sweet, R A and Chang, Y F and Tracy, R and DeKosky, S T} }