Hypocretin/Orexin, Sleep and Alzheimer's Disease.

Advances in translational research provide key opportunities to explore the physiological and pathological effects of sleep in different neurodegenerative diseases. Recent findings suggest that sleep-wakefulness dysfunctions may predispose to neurodegenerative disorders such as Alzheimer's disease (AD), and vice versa. New theories on the link between sleep and β-amyloid and tau secretion, accumulation and clearance, and its interaction with hypocretins/orexins (key neuropeptides regulating wakefulness) suggest mechanistic ways to better understand the impact of sleep alterations in the pathogenesis of AD. Further studies should validate whether changes in circadian rhythm and sleep-wakefulness patterns could be used for early AD diagnosis and as prognostic markers for cognitive decline. Longitudinal studies are needed, not only to validate these biomarker interactions and to determine the cause-effect relationship and the role of sleep-wakefulness behavior in the regulation of amyloid plaque and neurofibrillary tangle formation, but also to identify the best sleep therapies and related preventive strategies for AD.