Orexins regulate wakefulness and stabilize sleep–wake transitions; thus, selective antagonists (orexin receptor blockers) have been effective and are currently available for treating insomnia,143with emerging research suggesting, beyond insomnia treatment, potential roles in modulating disease course in AD.144PD patients might instead benefit from orexin agonists,145as PD is associated with lower orexin levels.146As discussed above, treatment of obstructive sleep apnea reduces the risk of neurovascular and neurodegenerative disorders. Here, HCRT is linked to Alzheimer disease.