P3-156: Elevated cardiovascular risk is associated with altered myelin content

Cardiovascular (CV) risk factors affect cognitive health and increase risk of dementia; however, the relationship between CV health and brain microstructure remains poorly understood. Myelinated white matter is a critical component to brain function and may be impacted by diminished CV health. In this work, we measured MRI T1 and T2 relaxation times as well as the myelin water fraction (MWF), a novel measure of myelin content, to examine the relationship between CV health and the myelo-architecture. Participants from the Wisconsin Registry for Alzheimer's Prevention study (N=73, 45-74 years, mean age = 62.22 ± 6.81 years) were imaged on a GE MR750 3T scanner. Multi-flip angle SPGR and bSSFP images were acquired and an actual flip-angle imaging strategy was used to correct for B1 inhomogeneities. Framingham CV risk scores were calculated for each subject. Three-pool mcDESPOT processing was used to calculate T1, T2, and MWF maps. A population-specific template was created using the high flip-angle SPGR image from each subject using the Advanced Normalization Tools software package and T1, T2, and MWF parameter maps were transformed to this template space. The relationship between each parameter and the Framingham CV risk factor was tested using FSL's randomise tool. We observed a positive relationship (p<0.05, uncorrected) between T2 and the CV risk scores and a negative relationship (p<0.05, uncorrected) between MWF and CV risk scores. These observed relationships suggest that as CV health decreases, myelinated white matter microstructure is altered in such a way that is consistent with decreasing myelin content and increasing free water (increasing T2).