Abnormal sleep blood pressure patterns are associated with diffusion tensor imaging along perivascular spaces index in cognitively impaired individuals

Blood pressure (BP) physiologically dips during sleep, and lack of dipping associates with adverse health outcomes and cognitive decline. Vascular pulsatility is the main driver of glymphatic cerebrospinal fluid transport, which removes metabolic waste products from the brain during sleep. We hypothesized that abnormal sleep BP patterns may affect glymphatic system health, and that this relationship may result in lower diffusion tensor imaging along perivascular spaces (DTI-ALPS) indices, a proposed neuroimaging index of glymphatic health. Twenty-one participants with mild-to-moderate cognitive impairment underwent 24-hour ambulatory BP monitoring, DTI-MRI and Alzheimer’s disease (AD) biomarker studies. Eight participants were classified as dippers (≥10%) and 13 as non-dippers (<10%), using sleep/awake systolic BP percentage of change. We found that non-dippers had lower DTI-ALPS even when adjusted by age and clinical stage (p=0.013). Stiffness measures (pulse wave velocity) were negatively correlated to DTI-ALPS (r=-0.5), but the association disappeared when adjusted by age. Positive AD biomarkers were more frequent in individuals who were classified as non-dippers of both systolic and diastolic BP, as compared to systolic and diastolic dippers (p=0.041). Our findings suggest that deviations of the physiological dipping sleep BP pattern may relate to poorer glymphatic function and increased AD pathology.