INTRODUCTION	Section 2 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

Background: Sleep disorders are among the most common clinical problems encountered in medicine, including in psychiatry. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) divides all sleep disorders into 3 general groups: primary, secondary to a mental disorder, and others, namely those related to a general medical condition or substance abuse.

Primary sleep disorders are presumed to result from an endogenous disturbance in sleep-wake generating or timing mechanisms, often complicated by behavioral conditioning. Primary sleep disorders are further subdivided into parasomnias and dyssomnias. Parasomnias are characterized by abnormal behavioral or physiological events in association with sleep, sleep stages, or sleep-wake transitions, rather than increased or decreased sleep. Parasomnias include nightmare disorder, sleep terror disorder, and sleepwalking disorder. Dyssomnias are characterized by abnormalities in the amount, quality, or timing of sleep. These include primary insomnia and hypersomnia, narcolepsy, breathing-related sleep disorder (ie, sleep apnea), and circadian rhythm sleep disorder. This article focuses primarily on insomnia, rather than the numerous other sleep disorders.

Primary insomnia is the general term for difficulty in initiating or maintaining sleep. Because sleep requirements vary from individual to individual, insomnia is considered clinically significant when a patient perceives the loss of sleep as a problem. Insomnia may be characterized further as acute (transient) or chronic.

Pathophysiology:

Rapid eye movement and nonrapid eye movement

Sleep is divided into 2 categories, rapid eye movement (REM) and nonrapid eye movement (NREM). Each of these sleep states is associated with distinct central nervous system activity.

NREM sleep is further divided into 4 progressive categories, termed stages 1-4 sleep. The arousal threshold rises with each stage of sleep, with stage 4 (delta) being the sleep state from which a person is least able to be aroused, characterized by high-amplitude slow waves.

REM sleep is characterized by muscle atonia, episodic REMs, and low-amplitude fast waves on electroencephalogram (EEG) readings. Dreaming occurs mainly during REM sleep.

Disturbances in the pattern and periodicity of REM and NREM sleep are often found when people aver to experiencing sleep disorders.

Sleep-wake cycles

Sleep-wake cycles are governed by a complex group of biological 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-hour cycle.

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 pontine reticular 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.

Frequency:

• In the US: Approximately one third of all Americans have sleep disorders at some point in their lives. Approximately 20-40% of adults report difficulty sleeping at some point each year. Approximately 17% of adults consider the problem to be serious. Sleep disorders are a common reason for patient visits throughout medicine. Approximately one third of adults have insufficient sleep syndrome. Twenty percent of adults report chronic insomnia.

Mortality/Morbidity:

• Chronic insomnia is associated with an increased risk of depression and accompanying danger of suicide, anxiety, excess disability, reduced quality of life, and increased use of health care resources.

• Insufficient sleep can result in industrial and motor vehicle crashes, somatic symptoms, cognitive dysfunction, depression, and decrements in daytime work performance owing to fatigue or sleepiness.

Sex:

• Primary insomnia is more common in women, with a female-to-male ratio of 3:2. Hormonal variations during the menstrual cycle or during menopause may cause disruptions in sleep.

• Obstructive sleep apnea is more common in men (4%) than in women (2.5%).

Age:

• Increasing age predisposes to sleep disorders (5% in persons aged 30-50 y and 30% in those aged 50 y or older).

• People who are elderly experience a decrease in total sleep time, with more frequent awakenings during the night.

• People who are elderly have a higher incidence of general medical conditions and are more likely to be taking medications that cause sleep disruption.

	CLINICAL	Section 3 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

History: Insomnia may present as decreased sleep efficiency or decreased total hours of sleep, with some associated decrease in productivity or well-being. Sleep quality is more important than the total number of hours slept because sleep requirements vary from person to person. Compare the total number of hours slept with each individual's lifelong normal night sleep time.

• Initial insomnia is characterized by difficulty falling asleep, with increased sleep latency (time between going to bed and falling asleep). Initial insomnia is frequently related to anxiety disorders.

• Middle insomnia refers to difficulty maintaining sleep. Decreased sleep efficiency is present, with fragmented unrestful sleep and frequent waking during the night. Middle insomnia may be associated with medical illness, pain syndromes, or depression.

• In terminal insomnia, also referred to as early morning wakening, patients consistently wake up earlier than needed. This symptom is frequently associated with major depression.

• Alterations of the sleep-wake cycle may be a sign of circadian rhythm disturbances, such as those caused by jet lag and shift work.

• Hypersomnia, or excessive daytime sleepiness, is often attributable to ongoing sleep deprivation or poor quality sleep for reasons ranging from sleep apnea to substance abuse or medical problems.

• In delayed sleep phase syndrome, the patient is unable to fall asleep until very early morning. As time progresses, the onset of sleep becomes progressively delayed.

• Sleepwalking, also called somnambulism, refers to episodes of complex behaviors during NREM sleep (stages 3 and 4) of which the patient is amnestic afterward.

• Nightmares are repeated awakenings from sleep caused by vivid and distressing recall of dreams. Nightmares usually occur during the second half of the sleep period. Upon wakening from the dream, the person rapidly reorients to time and place.

• Night terrors are recurrent episodes of abrupt awakening from sleep characterized by a panicky scream, with intense fear and autonomic arousal. The individual usually has no recall of the details of the event and is unresponsive during the episode. Night terrors occur during the first third of the night, during stages 3 and 4 of NREM sleep.

• The bed partner of patients who snore may provide a history of snoring. Such a history may help identify whether a patient experiences obstructive sleep apnea.

Causes: The major causes of insomnia may be divided into medical conditions, psychological conditions, and environmental problems.

• Medical conditions

• Cardiac conditions 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 conditions affecting sleep are related to hyperthyroidism, menopause, the menstrual cycle, pregnancy, and hypogonadism in elderly men.

• Pulmonary conditions include chronic obstructive pulmonary disease, asthma, central alveolar hypoventilation (the Ondine curse), and obstructive sleep apnea syndrome (associated with snoring).

• Gastrointestinal conditions include gastroesophageal reflux disease.

• Hematological conditions include paroxysmal nocturnal hemoglobinuria, which is a rare, acquired, hemolytic anemia associated with brownish-red morning urine.

• Substances that may result in insomnia include stimulants, opioids, caffeine, and alcohol, or, withdrawal from any of these also may cause insomnia.

• Medications implicated in insomnia include decongestants, corticosteroids, and bronchodilators.

• Other conditions include fever, pain, and infection.

• Psychiatric conditions: Bear in mind that the major psychiatric conditions now are known to have a biological basis and constitute a subset of medical conditions.

• Depression may cause alterations in REM sleep. As many as 40% of people with depression have insomnia.

• Posttraumatic stress disorder (PTSD) can produce vivid and terrifying nightmares.

• Anxiety disorders predispose to insomnia. The most common of these are generalized anxiety disorder, panic disorder, and anxiety disorders not otherwise specified.

• Thought disorders and misperception of sleep state are other potential states that cause insomnia.

• Psychotropic medications, such as antidepressants, may interfere with normal REM sleep patterns.

• Rebound insomnia from benzodiazepines or other hypnotic agents is common.

• Environmental problems

• Stressful or life-threatening events (eg, bereavement, PTSD) may cause insomnia.

• Shift work may disturb the sleep cycle, as might jet lag or changes in altitude.

• Sleep deprivation may occur as a result of an overly warm sleeping environment, environmental noise, or frequent intrusions (such as in an intensive care unit setting).