Sleep Disorders

Sleep Disorders
* Author: Roy H Lubit, MD, PhD; Chief Editor: Iqbal Ahmed, MBBS, FRCPsych (UK)
Background
Sleep disorders are among the most common clinical problems encountered in medicine and psychiatry. Inadequate or nonrestorative sleep can markedly impair a patient’s quality of life.[1] Sleep disorders may be primary or may result from a variety of psychiatric and medical conditions.Primary sleep disorders result from an endogenous disturbance in sleep-wake generating or timing mechanisms, often complicated by behavioral conditioning. They may be divided into the following 2 broad categories:
* Parasomnias – These are unusual experiences or behaviors that occur during sleep; they include sleep terror disorder and sleepwalking (which occur during stage 4 sleep) andnightmare disorder (which occurs during rapid eye movement [REM] sleep).
* Dyssomnias – These are characterized by abnormalities in the amount, quality, or timing of sleep; they include primary insomnia and hypersomnia, narcolepsy, breathing-related sleep disorder (ie, sleep apnea), and circadian rhythm sleep disorder
It is important to distinguish these primary sleep disorders from secondarysleep disorders. At times, determining whether anxiety and depression are causing sleep problems or the anxiety and depression are secondary to a primary sleep problem is difficult. (See Anxiety Disorders and Depression.)
Primary insomnia is the general term for difficulty in initiating or maintaining sleep. Because sleep requirements vary from individual to individual, insomnia is consideredclinically significant when a patient perceives the loss of sleep as a problem. Insomnia may be further characterized as either acute (transient) or chronic.
Next Section: Pathophysiology
Pathophysiology
Sleep is divided into the following 2 categories, each of which is associated with distinct patterns of central nervous system (CNS) activity:
* REM sleep – This is characterized by muscleatony, episodic REMs, and low-amplitude fast waves on electroencephalography (EEG); dreaming occurs mainly during REM sleep
* Non-REM (NREM) sleep – This is further subdivided into 4 progressive categories, termed stages 1-4 sleep; the arousal threshold rises with each stage, and stage 4 (delta), characterized by high-amplitude slow waves, is the sleep state from which arousal is most difficultDisturbances in the pattern and periodicity of REM and NREM sleep are often found when people admit to experiencing sleep disorders.
Sleep-wake cycles are governed by a complex group of biologic processes that serve as internal clocks. The suprachiasmatic nucleus, located in the hypothalamus, is thought to be the body’s anatomic timekeeper, responsible for the release of melatonin on a 25-hourcycle. The pineal gland secretes less melatonin when exposed to bright light; therefore, the level of this chemical is lowest during the daytime hours of wakefulness.
Multiple neurotransmitters are thought to play a role in sleep. These include serotonin from the dorsal raphe nucleus, norepinephrine contained in neurons with cell bodies in the locus ceruleus, and acetylcholine from the pontinereticular formation. Dopamine, on the other hand, is associated with wakefulness.
Abnormalities in the delicate balance of all of these chemical messenger systems may disrupt various physiologic, biologic, behavioral, and EEG parameters responsible for REM (ie, active) sleep and NREM (slow-wave) sleep.
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Etiology
The major causes of insomnia may bedivided into medical conditions, psychological conditions, and environmental problems.
Medical conditions
Cardiac conditions that may give rise to disordered sleep include ischemia and congestive heart failure. Neurologic conditions include stroke, degenerative conditions, dementia, peripheral nerve damage, myoclonic jerks, restless leg syndrome, hypnic jerk, and central sleep apnea. Endocrine...