AbstractBackgroundGlymphatic exchange of interstitial solutes may underlie the observed clinical association between sleep, aging, and Alzheimer’s Disease (AD). Furthermore, glymphatic function is currently primarily measured by contrast‐based (CE) MRI, limiting its clinical utility. In this work we test a wearable device to assess sleep architecture and a diffusion‐based intravoxel incoherent motion (IVIM) protocol to detect sleep‐related changes in the glymphatic system at two sites.Method Site 1: We recruited 13 participants (age = 62±3 yrs. old, 4F) and assessed them prior to and following overnight sleep and sleep deprivation. Sleep efficiency, relative slow delta power, N2, N3, and REM durations were measured with the wearable device. Using CE‐MRI, delayed contrast enhancement in the subarachnoid (SASe) was measured at ∼4 hrs after contrast injection to assess brain parenchymal solute clearance during a second recovery sleep opportunity. For contrast‐free MRI, we measured slow subarachnoid CSF flow (D*) in the SAS using IVIM at night and in the morning. Cognitive assessments were conducted in the morning only. Site 2: We conducted an identical sleep/sleep deprivation study (N = 10, age = 54±5 yrs. old, 9F), but without CE MRI. We tested the correlation between SASe and D*. Next, we compared changes in D* between a night of sleep and sleep deprivation and tested associations with sleep parameters.Result A. Change in D* after sleep or awake opportunity was significantly associated with SASe (p = 0.05) Greater SAS D* was associated with lesser contrast in the SAS. B. Although not significant, D* reproducibly decreases with sleep deprivation and remains unchanged after sleep. C‐D. Differences in D* during sleep were significantly associated with slow wave spindle number (p = 0.03) and N3 duration (p = 0.04). E. D* measurement concurrent with PVT administrations showed that while greater D* after staying awake was associated with longer reaction times, greater D* after a night of sleep was associated with shorter reaction times.ConclusionWith a wearable device, remote sleep assessment was successfully performed. IVIM‐derived D* was associated with CE MRI measures in the SAS providing a non‐invasive alternative to study brain fluid transport. D* showed associations with sleep parameters as well as sleep‐associated cognition.