[Sleep Disorders].

Insomnia is a common sleep disorder that, owing to difficulties falling asleep or maintaining sleep and/or early morning awakening, causes daytime functional impairment. Other sleep disorders include sleep-related breathing disorders; sleep-related movement disorders, such as periodic limb movement disorder and restless legs syndrome; parasomnias, such as rapid eye movement sleep behavior disorder and sleepwalking; and central disorders of hypersomnolence, such as narcolepsy. This article describes sleep disorders that are routinely observed in daily clinical practice.