Reduced slow‐wave sleep is associated with greater tau accumulation and reduced cortical thickness in the temporal lobe

Abstract

AbstractBackgroundSlow wave sleep (SWS) plays an important role in overnight memory consolidation and promotes overnight clearance of amyloid‐β and tau proteins. Reduced SWS has been associated with higher amyloid burden in CSF in preclinical stages of Alzheimer’s disease (AD). However, little is known about the relationship between SWS, tau burden and neurodegeneration in cognitively unimpaired (CU) adults. Thus, we investigated the relationships between slow‐wave sleep, regional tau PET (18F‐flortaucipir; FTP‐PET) and temporal lobe cortical thickness in cognitively unimpaired adults at risk of AD.MethodsThis study included 39 CU adults from the Harvard Aging Brain Study (mean age 74.6 years, 61.5% females) who underwent at‐home polysomnography (PSG; Compumedics Somte), tau PET (FTP‐PET, amyloid PET (PIB‐PET) and MRI (Table 1). We used separate multivariate linear regressions to assess associations between the percentage of slow‐wave sleep (SWS) and tau PET signal in the following ROIs: entorhinal cortex, inferior temporal cortex, and a temporal composite comprised of entorhinal, inferior temporal, middle temporal and fusiform cortices. Primary analyses were adjusted for age and sex. Secondary analyses also adjusted for global amyloid (PiB‐PET) burden. Lastly, we investigated the relationship between SWS and cortical thickness in the same ROIs, assessed using FreeSurfer v6.0.ResultsLower percentage of SWS was associated with greater tau burden in entorhinal (p = 0.036), inferior temporal (p = 0.011), and temporal composite ROIs (p = 0.005). Associations between reduced SWS and greater FTP‐PET signal in the inferior temporal cortex and temporal composite ROI remained after controlling for PiB‐PET (p = 0.028; p = 0.017, respectively; Table 2). Additionally, lower SWS was associated with reduced cortical thickness in the entorhinal (p = 0.031), inferior temporal (p = 0.023) and temporal composite ROIs (p = 0.002) (Table 3).ConclusionsLower SWS in CU adults was associated with higher tau burden in regions of the temporal lobe that are commonly sites of early tau accumulation. These effects were independent of amyloid burden, suggesting disrupted sleep may lead to increased tau accumulation via an amyloid‐independent pathway. Importantly, lower SWS was also associated with reduced cortical thickness in temporal regions, suggesting that disrupted sleep may be tied to early AD‐related neuronal loss in the temporal lobe.