Chapter 17: Sleep and Sleep–Wake Disorders

Sleep is regulated by coordinating neural structures like the midbrain reticular formation, thalamus, and cerebral cortex, and alternates between two primary states: Non-Rapid Eye Movement (NREM), or slow-wave sleep, which progresses through four deepening stages characterized by specific brain wave activity like theta and delta waves; and Rapid Eye Movement (REM) sleep, a highly active state marked by suppressed muscle tone, fluctuating vital signs, and vivid dreaming. The timing of this cycle is governed by the 24-hour circadian rhythm, controlled by the suprachiasmatic nucleus (SCN), which interacts with the pineal gland to regulate melatonin release based on the light–dark cycle. Diagnosis of sleep disturbances relies on clinical history, sleep logs, actigraphy, and objective laboratory tests such as polysomnography (PSG). Specific disorders covered include Insomnia—difficulty initiating or maintaining sleep—treated often with cognitive-behavioral therapy (CBT) and improved sleep hygiene; and Narcolepsy, a central disorder of excessive sleepiness that may involve cataplexy and is linked to hypocretin deficiency. The chapter also details Circadian Rhythm Sleep–Wake Disorders (like Delayed Sleep-Wake Phase Disorder and jet lag), Sleep-Related Movement Disorders (including Restless Legs Syndrome and Periodic Limb Movement Disorder), and the significant public health concern of Obstructive Sleep Apnea (OSA), caused by upper airway collapse during sleep and treated primarily with Continuous Positive Airway Pressure (CPAP). Finally, undesirable events known as Parasomnias (e.g., sleepwalking and sleep terrors, which occur during deep NREM sleep) are explored, along with the specific changes in sleep architecture and increased prevalence of sleep problems observed across both pediatric and older adult populations.