Heterogeneity in the links between sleep arousals, amyloid-β, and cognition.

BACKGROUNDTight relationships between sleep quality, cognition, and amyloid-β (Aβ) accumulation, a hallmark of Alzheimer's disease (AD) neuropathology, have been shown. Sleep arousals become more prevalent with aging and are considered to reflect poorer sleep quality. However, heterogeneity in arousals has been suggested while their associations with Aβ and cognition are not established.METHODSWe recorded undisturbed night-time sleep with EEG in 101 healthy individuals aged 50-70 years, devoid of cognitive and sleep disorders. We classified spontaneous arousals according to their association with muscular tone increase (M+/M-) and sleep stage transition (T+/T-). We assessed cortical Aβ burden over earliest affected regions via PET imaging and assessed cognition via neuropsychological testing.RESULTSArousal types differed in their oscillatory composition in θ (4-8 Hz) and β (16-30 Hz) EEG bands. Furthermore, T+M- arousals, interrupting sleep continuity, were positively linked to Aβ burden (P = 0.0053, R²β* = 0.08). By contrast, more prevalent T-M+ arousals, upholding sleep continuity, were associated with lower Aβ burden (P = 0.0003, R²β* = 0.13), and better cognition, particularly over the attentional domain (P < 0.05, R²β* ≥ 0.04).CONCLUSIONContrasting with what is commonly accepted, we provide empirical evidence that arousals are diverse and differently associated with early AD-related neuropathology and cognition. This suggests that sleep arousals, and their coalescence with other brain oscillations during sleep, may actively contribute to the beneficial functions of sleep and constitute markers of favorable brain and cognitive health trajectories.TRIAL REGISTRATIONEudraCT 2016-001436-35.FUNDINGFRS-FNRS Belgium (FRSM 3.4516.11), Actions de Recherche Concertées Fédération Wallonie-Bruxelles (SLEEPDEM 17/27-09), ULiège, and European Regional Development Fund (Radiomed Project).