Abstract 9: Pervasive White Matter Microstructure Dysintegrity Related To High Blood Pressure Among Asymptomatic Population

Abstract

Background: Blood pressure is the strongest contributor to clinically evident cerebrovascular disease. We investigated the role of blood pressure on white matter (WM) microstructure among asymptomatic individuals without clinically evident cerebrovascular disease. Methods: We conducted a nested study within the UK Biobank, restricting our analysis to participants without cerebrovascular disease or dementia and with available brain diffusion tensor imaging (DTI). We tested for association between systolic blood pressure (SBP) and six different DTI metrics: fractional anisotropy (FA), mean diffusivity (MD), tensor mode (MO), intra-cellular volume fraction (ICVF), isotropic or free water volume fraction (ISOVF), and orientation dispersion index (OD) across 48 WM tracts using multivariable linear regression adjusted for potential confounders. We used Bonferroni-corrected p-values (0.05/48) for statistical significance. Results: We analyzed 33,440 participants. Mean age was 63.0 (SD 7.7), and 17,688 (53%) were female. Higher SBP is independently associated with pervasive decrease in FA and ICVF and increase in MD (Figure), after adjustment for vascular risk-factors. SBP was also associated with lower neurite OD (a more specific metric of axonal damage) in bilateral posterior corona radiata, external capsule, medial lemniscus, and corticospinal tracs. FA and OD of external capsule and posterior corona radiata had the largest drop per 10 mmHg increase of SBP (steepest slope). Conclusions: Higher SBP is associated with pervasive WM microstructure dysintegrity in asymptomatic individuals without evident cerebrovascular disease. DTI metrics of the posterior corona radiata and external capsule are most reflective of variations in SBP and may provide a potential biomarker to assess subtle WM microstructural damage in hypertensive patients or monitor treatment response in clinical trials.