Association of sleep quality and diffusion MRI derived interstitial fluid content – insights in cerebral waste clearance

Abstract

AbstractBackgroundDisruptions in sleep are associated with Alzheimer’s disease (AD) progression. As cerebral waste clearance is most active during sleep, these reductions in sleep quality could induce impaired clearance function. Waste products are washed through the parenchyma in the interstitial fluid (ISF), its volume being regulated by the sleep‐wake cycle. A smaller ISF‐volume is found in awake states and after sleep deprivation. IntraVoxel Incoherent Motion (IVIM) MRI can detect the diffusion of cerebral ISF (Dint) and its volume fraction (fint).Using IVIM, the current exploratory study investigates whether alterations in a proxy of ISF‐volume (fint) are related to hours of sleep or self‐reported sleep quality.MethodTwenty neurotypical elderly subjects (Table 1) underwent ultra‐high field MRI (7T research system, Siemens Healthcare GmbH, Erlangen, Germany) (Table 2).The intermediate diffusion components (Dint) in the range 1.5*10‐3<Diffusivity<4.0*10‐3 mm2/s were calculated using spectral analysis (Figure 1). The relative signal contribution of Dint was quantified by the ISF‐fraction (fint). Median fint values were extracted from the white matter (WM) and gray matter (GM).Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI). In addition to the clinically used total PSQI (sum of all 7 components), the PSQI1 (Subjective sleep quality) and PSQI3 (Sleep duration) components were considered.Pearson correlations were computed between the PSQI scores and fint for WM and GM. To check for potential confounding influences, partial correlations were performed adjusting for age and time of MRI‐acquisition.ResultThe sample characteristics and descriptive statistics are summarized in Table 1. Worse reported sleep quality (PSQI1) significantly relates to lower WM fint (Table 3 and Figure 2). After adjusting for potential confounding influences, a trend towards significance remained (R=‐0.437, p=0.061).ConclusionThe current explorative study identified a lower diffusion MRI‐derived proxy of ISF‐volume in the WM of subjects who reported a subjective feeling of long‐term sleep deprivation. A reduction in ISF‐volume may leave less space for waste products, such as soluble Amyloid‐beta, to be cleared from in‐between the cells. Thereby, this study puts forward a potential method for future studies to investigate impaired clearance function in relation to sleep in patients with AD pathology.