P3-070: CSF Total tau and gray matter density in Alzheimer's disease–specific brain regions: A study of normal aging

CSF Total tau (T-tau) is a reliable predictor of Alzheimer's disease (AD) at the MCI stage, but little is known about its ability to recognize pathology in earlier clinical stages. Using MRI, we tested the validity of T-tau as an AD risk marker in a cognitively normal population. Our hypothesis was that CSF T-tau levels would be correlated with gray matter (GM) density in AD-related brain regions. The study included 93 cognitively healthy individuals (age 63.1±9.6, range 40–86 years; 66% women). All signed IRB approved written informed consent, and underwent a comprehensive clinical assessment, lumbar puncture and MRI. CSF T-tau was determined using the Innogenetics kit. For image analysis, voxel based morphometry (VBM) was performed with MATLAB 7.1 and Statistical Parametric Mapping (SPM'2) procedures. All high resolution scans were realigned, normalized and segmented to GM, white matter and CSF images. The GM images were re-normalized to GM templates and smoothed. First, the measures of global GM density were extracted and a regression model (SPSS 12.0 Chicago, IL) was employed to evaluate the association between T-tau and global GM. Second, a regression model (SPM'2) was used to assess the relationship between the T-tau and GM density on a regional basis. Results were examined over the whole brain at p<0.001 with a minimum cluster size of 100 voxels. Anatomical location of areas showing GM effects was described using the Talairach and Tournoux coordinates. Global effects: Global GM density was inversely associated with T-tau (F1,91=5.8, p