Sleep Disorders
I. General Introduction
Sleep is a universal behavior that has been demonstrated in every animal species studied, from insects to mammals. It is one of the most significant of human behaviors, occupying roughly one third of human life. Approximately 30% of adults in the United States experience a sleep disorder during their lifetime, and over half do not seek treatment. Lack of sleep can lead to the inability to concentrate, memory complaints, deficits in neuropsychological testing, and decreased libido. Additionally, sleep disorders can have serious consequences, including fatal accidents related to sleepiness. Disturbed sleep can be a primary diagnosis itself or a component of another medical or psychiatric disorder (Table 21-1). Careful diagnosis and specific treatment are essential. Female sex, advanced age, medical and mental disorders, and substance abuse are associated with an increased prevalence of sleep disorders.
In the text revision of the fourth edition of the Diagnostic Statistical Manual of Mental Disorders (DSM-IV-TR), sleep disorders are classified on the basis of clinical diagnostic criteria and presumed etiology. The three major categories are (1) primary sleep disorders, (2) sleep disorders related to another mental disorder, and (3) other sleep disorders (due to a general medical condition and substance induced).
A. Sleep stages.
Sleep is comprised of two physiological states: rapid eye movement (REM) sleep and nonrapid eye movement (NREM) sleep. NREM sleep consists of four sleep stages, named stage I through stage IV. Dreaming occurs mostly in REM sleep, but additionally, some dreaming occurs in stages III and IV sleep. Sleep is measured with a polysomnograph, which simultaneously measures brain activity (electroencephalogram [EEG]), eye movement (electrooculogram), and muscle tone (electromyogram). Other physiological tests can be applied during sleep and measured along with the above. EEG findings are used to describe sleep stages (Table 21-2).
It takes the average person 15 to 20 minutes to fall asleep; this is the sleep latency. During the next 45 minutes, one descends from stages I and II of sleep to stages III and IV. Stages III and IV comprise the deepest sleep; that is, the largest stimulus is needed to arouse one in these stages of sleep. Approximately 45 minutes after stage IV begins, the first REM period is reached. Therefore, the average REM latency (the time from sleep onset to REM onset) is 90 minutes. Throughout the night, one cycles through the four stages of sleep followed by REM sleep. As the night progresses, each REM period becomes longer, and stages III and IV disappear. Hence, further into the night, persons sleep more lightly and dream (mostly REM sleep) more. The sleep stages in an adult are approximately 25% REM sleep and 75% NREM sleep, consisting of 5% in stage I, 45% in stage II, 12% in stage III, and 13% in stage IV.
Table 21-1 Common Causes of Insomnia | ||||||||||||
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B. Characteristics of REM sleep (also called paradoxical sleep)
Autonomic instability
Increased heart rate (HR), blood pressure (BP), and respiratory rate (RR).
Increased variability in HR, BP, and RR from minute to minute.
Appears similar to an awake person on EEG.
Tonic inhibition of skeletal muscle tone leading to paralysis.
Rapid eye movements.
Dreaming.
Reduced hypercapnic respiratory drive, no increase in tidal volume as partial pressure of carbon dioxide decreases.
Table 21-2 Sleep Stages
Awake:
Low voltage, random, very fast
Drowsy:
Alpha waves (8–12 CPS), random and fast
Stage I:
Theta waves (3–7 CPS), slight slowing
Stage II:
Further slowing, K complex (triphasic complexes), sleep spindles, true sleep onset
Stage III:
Delta waves (0.5–2 CPS), high amplitude slow waves.
Stage IV:
At least 50% delta waves. Stages III and IV comprise delta sleep.
REM:
Sawtooth waves, similar to drowsy sleep on EEG
CPS, cycles per second.
Relative poikilothermia (cold-bloodedness).
Penile tumescence or vaginal lubrication.
Reduced sensitivity to sounds.
II. Primary Sleep Disorders
The DSM-IV-TR defines primary sleep disorders as those not caused by another mental disorder, a physical condition, or a substance but, rather, are caused by an abnormal sleep–wake mechanism and often by conditioning. The two main primary sleep disorders are dyssomnias and parasomnias.
A. Dyssomnias.
A heterogeneous group of sleep disorders characterized by abnormalities in the quality, amount, or timing of sleep.
Primary insomnia. Diagnosed when the chief complaint is difficulty in initiating or maintaining sleep or nonrestorative sleep for at least 1 month.
Insomnia is the most common type of sleep disorder.
Causes are listed in Table 21-1.
Treatment includes deconditioning techniques, transcendental meditation, relaxation tapes, sedative–hypnotic drugs, and nonspecific measures, such as sleep hygiene, described in Table 21-3.
Primary hypersomnia. Diagnosed when there is no other cause found for greater than 1 month of excessive somnolence (daytime sleepiness) or excessive amounts of daytime sleep. Usually begins in childhood. Treatment consists of stimulant drugs.
Narcolepsy
Narcolepsy consists of the following characteristics:
Excessive daytime somnolence (sleep attacks) is the primary symptom of narcolepsy.
Distinguished from fatigue by irresistible sleep attacks of short duration (less than 15 minutes).
Sleep attacks may be precipitated by monotonous or sedentary activity.
Naps are highly refreshing and effects usually last 30 to 120 minutes.
Table 21-3 Nonspecific Measures to Induce Sleep (Sleep Hygiene)
- Arise at the same time daily.
- Limit daily in-bed time to the usual amount before the sleep disturbance.
- Discontinue CNS-acting drugs (caffeine, nicotine, alcohol, stimulants).
- Avoid daytime naps (except when sleep chart shows they induce better night sleep).
- Establish physical fitness by means of a graded program of vigorous exercise early in the day.
- Avoid evening stimulation; substitute radio or relaxed reading for television.
- Try very hot, 20-minute, body temperature–raising bath soaks near bedtime.
- Eat at regular times daily; avoid large meals near bedtime.
- Practice evening relaxation routines, such as progressive muscle relaxation or meditation.
- Maintain comfortable sleeping conditions.
From Regestein QR. Sleep disorders. In: Stoudemire A, ed. Clinical Psychiatry for Medical Students. Philadelphia: Lippincott, 1990:578.
Cataplexy
Reported by over 50% of narcoleptic patients.
Brief (seconds to minutes) episodes of muscle weakness or paralysis.
No loss of consciousness if episode is brief.
When attack is over, the patient is completely normal.
May manifest as partial loss of muscle tone (weakness, slurred speech, buckled knees, dropped jaw).
Often triggered by laughter (common), anger (common), athletic activity, excitement or elation, sexual intercourse, fear, or embarrassment.
Flat affect or lack of expressiveness develops in some patients as an attempt to control emotions.
A diagnosis of cataplexy automatically results in a diagnosis of narcolepsy. If cataplexy does not occur, multiple other characteristics are necessary for the diagnosis of narcolepsy.
Sleep paralysis
Temporary partial or complete paralysis in sleep–wake transitions.
Conscious but unable to move or open eyes.
Most commonly occurs on awakening.
Generally described as an anxiety-provoking, “scary” event.
Generally lasts less than 1 minute.
Reported by 25% to 50% of the general population, though for a much shorter duration.
Hypnagogic and hypnopompic hallucinations
Dreamlike experience during transition from wakefulness to sleep and vice versa.
Vivid auditory or visual hallucinations or illusions.
Sleep-onset REM periods (SOREMPs)
Defined as appearance of REM within 15 minutes of sleep onset (normally approximately 90 minutes).
Narcolepsy can be distinguished from other disorders of excessive daytime sleepiness by SOREMPs seen on polysomnographic recording.Related posts:
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