Water exchange rate across the blood-brain barrier is associated with CSF amyloid-ß 42 in healthy older adults.

INTRODUCTION: We tested if water exchange across the blood-brain barrier (BBB), estimated with a noninvasive magnetic resonance imaging (MRI) technique, is associated with cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) and neuropsychological function. METHODS: Forty cognitively normal older adults (67-86 years old) were scanned with diffusion-prepared, arterial spin labeling (DP-ASL), which estimates water exchange rate across the BBB (kw ). Participants also underwent CSF draw and neuropsychological testing. Multiple linear regression models were run with kw as a predictor of CSF concentrations and neuropsychological scores. RESULTS: In multiple brain regions, BBB kw was positively associated with CSF amyloid beta (Aß)42 concentration levels. BBB kw was only moderately associated with neuropsychological performance. DISCUSSION: Our results suggest that low water exchange rate across the BBB is associated with low CSF Aß42 concentration. These findings suggest that kw may be a promising noninvasive indicator of BBB Aß clearance functions, a possibility which should be further tested in future research.