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SLEEP DISORDERS
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The DSM-IV classifies sleep disorders
based on what causes them. Primary sleep disorders are distinguished
from those that are not caused by other mental disorders,
prescription medications, substance abuse, or medical conditions.
The two major categories of primary sleep disorders are the
dyssomnias and the parasomnias.
Dyssomnias
Dyssomnias are primary sleep disorders in which the patient suffers
from changes in the amount, restfulness, and timing of sleep. The
most important dyssomnia is primary insomnia, which is defined as
difficulty in falling asleep or remaining asleep that lasts for at
least one month. It is estimated that 35% of adults in the United
States experience insomnia during any given year, but the number of
these adults who are experiencing true primary insomnia is unknown.
Primary insomnia can be caused by a traumatic event related to sleep
or bedtime, and it is often associated with increased physical or
psychological arousal at night. People who experience primary
insomnia are often anxious about not being able to sleep. The person
may then associate all sleep-related things (their bed, bedtime,
etc.) with frustration, making the problem worse. The person then
becomes more stressed about not sleeping. Primary insomnia usually
begins when the person is a young adult or in middle age.
Hypersomnia is a condition marked by excessive sleepiness during
normal waking hours. The patient has either lengthy episodes of
daytime sleep or episodes of daytime sleep on a daily basis even
though he or she is sleeping normally at night. In some cases,
patients with primary hypersomnia have difficulty waking in the
morning and may appear confused or angry. This condition is
sometimes called sleep drunkenness and is more common in males. The
number of people with primary hypersomnia is unknown, although 5-10%
of patients in sleep disorder clinics have the disorder. Primary
hypersomnia usually affects young adults between the ages of 15- 30.
Nocturnal myoclonus and restless legs syndrome (RLS) can cause
either insomnia or hypersomnia in adults. Patients with nocturnal
myoclonus wake up because of cramps or twitches in the calves. These
patients feel sleepy the next day. Nocturnal myoclonus is sometimes
called periodic limb movement disorder (PLMD). RLS patients have a
crawly or aching feeling in their calves that can be relieved by
moving or rubbing the legs. RLS often prevents the patient from
falling asleep until the early hours of the morning, when the
condition is less intense.
Kleine-Levin syndrome is a recurrent form of hypersomnia that
affects a person three or four times a year. Doctors do not know the
cause of this syndrome. It is marked by two to three days of
sleeping 18-20 hours per day, hypersexual behavior, compulsive
eating, and irritability. Men are three times more likely than women
to have the syndrome. As of 1998, there is no cure for this disorder.
Narcolepsy is a dyssomnia characterized by recurrent "sleep attacks"
that the patient cannot fight. The sleep attacks are about 10-20
minutes long. The patient feels refreshed by the sleep, but
typically feels sleepy again several hours later. Narcolepsy has
three major symptoms in addition to sleep attacks: cataplexy,
hallucinations, and sleep paralysis. Cataplexy is the sudden loss of
muscle tone and stability ("drop attacks"). Hallucinations may occur
just before falling asleep (hypnagogic) or right after waking up (hypnopompic)
and are associated with an episode of REM sleep. Sleep paralysis
occurs during the transition from being asleep to waking up. About
40% of patients with narcolepsy have or have had another mental
disorder. Although narcolepsy is often regarded as an adult disorder,
it has been reported in children as young as three years old. Almost
18% of patients with narcolepsy are 10 years old or younger. It is
estimated that 0.02-0.16% of the general population suffer from
narcolepsy. Men and women are equally affected.
Breathing-related sleep disorders are syndromes in which the
patient's sleep is interrupted by problems with his or her breathing.
There are three types of breathing-related sleep disorders:
Obstructive sleep apnea syndrome. This is the most common form of
breathing-related sleep disorder, marked by episodes of blockage in
the upper airway during sleep. It is found primarily in obese people.
Patients with this disorder typically alternate between periods of
snoring or gasping (when their airway is partly open) and periods of
silence (when their airway is blocked). Very loud snoring is a clue
to this disorder.
Central sleep apnea syndrome. This disorder is primarily found in
elderly patients with heart or neurological conditions that affect
their ability to breathe properly. It is not associated with airway
blockage and may be related to brain disease.
Central alveolar hypoventilation syndrome. This disorder is found
most often in extremely obese people. The patient's airway is not
blocked, but his or her blood oxygen level is too low.
Mixed-type sleep apnea syndrome. This disorder combines symptoms of
both obstructive and central sleep apnea.
Circadian rhythm sleep disorders are dyssomnias resulting from a
discrepancy between the person's daily sleep/wake patterns and
demands of social activities, shift work, or travel. The term
circadian comes from a Latin word meaning daily. There are three
circadian rhythm sleep disorders. Delayed sleep phase type is
characterized by going to bed and arising later than most people.
Jet lag type is caused by travel to a new time zone. Shift work type
is caused by the schedule of a person's job. People who are
ordinarily early risers appear to be more vulnerable to jet lag and
shift work-related circadian rhythm disorders than people who are
"night owls". There are some patients who do not fit the pattern of
these three disorders and appear to be the opposite of the delayed
sleep phase type. These patients have an advanced sleep phase
pattern and cannot stay awake in the evening, but wake up on their
own in the early morning.
Parasomnias
Parasomnias are primary sleep disorders in which the patient's
behavior is affected by specific sleep stages or transitions between
sleeping and waking. They are sometimes described as disorders of
physiological arousal during sleep.
Nightmare disorder is a parasomnia in which the patient is
repeatedly awakened from sleep by frightening dreams and is fully
alert on awakening. The actual rate of occurrence of nightmare
disorder is unknown. Approximately 10-50% of children between three
and five years old have nightmares. They occur during REM sleep,
usually in the second half of the night. The child is usually able
to remember the content of the nightmare and may be afraid to go
back to sleep. More females than males have this disorder, but it is
not known whether the sex difference reflects a difference in
occurrence or a difference in reporting. Nightmare disorder is most
likely to occur in children or adults under severe or traumatic
stress.
Sleep terror disorder is a parasomnia in which the patient awakens
screaming or crying. The patient also has physical signs of arousal,
like sweating, shaking, etc. It is sometimes referred to as pavor
nocturnus. Unlike nightmares, sleep terrors typically occur in stage
3 or stage 4 NREM sleep during the first third of the night. The
patient may be confused or disoriented for several minutes and
cannot recall the content of the dream. He or she may fall asleep
again and not remember the episode the next morning. Sleep terror
disorder is most common in children 4-12 years old and is outgrown
in adolescence. It affects about 3% of children. Fewer than 1% of
adults have the disorder. In adults, it usually begins between the
ages of 20 and 30. In children, more males than females have the
disorder. In adults, men and women are equally affected.
Sleepwalking disorder, which is sometimes called somnambulism,
occurs when the patient is capable of complex movements during
sleep, including walking. Like sleep terror disorder, sleepwalking
occurs during stage 3 and stage 4 NREM sleep during the first part
of the night. If the patient is awakened during a sleepwalking
episode, he or she may be disoriented and have no memory of the
behavior. In addition to walking around, patients with sleepwalking
disorder have been reported to eat, use the bathroom, unlock doors,
or talk to others. It is estimated that 10-30% of children have at
least one episode of sleepwalking. However, only 1-5% meet the
criteria for sleepwalking disorder. The disorder is most common in
children 8-12 years old. It is unusual for sleepwalking to occur for
the first time in adults.
Unlike sleepwalking, REM sleep behavior disorder occurs later in the
night and the patient can remember what they were dreaming. The
physical activities of the patient are often violent.
Sleep disorders related to other conditions
In addition to the primary sleep disorders, the DSM-IV specifies
three categories of sleep disorders that are caused by or related to
substance use or other physical or mental disorders.
Sleep disorders related to mental disorders
Many mental disorders, especially depression or one of the anxiety
disorders, can cause sleep disturbances. Psychiatric disorders are
the most common cause of chronic insomnia.
Sleep disorders due to medical conditions
Some patients with chronic neurological conditions like Parkinson's
disease or Huntington's disease may develop sleep disorders. Sleep
disorders have also been associated with viral encephalitis, brain
disease, and hypo- or hyperthyroidism.
Substance-induced sleep disorders
The use of drugs, alcohol, and caffeine frequently produces
disturbances in sleep patterns. Alcohol abuse is associated with
insomnia. The person may initially feel sleepy after drinking, but
wakes up or sleeps fitfully during the second half of the night.
Alcohol can also increase the severity of breathing-related sleep
disorders. With amphetamines or cocaine, the patient typically
suffers from insomnia during drug use and hypersomnia during drug
withdrawal. Opioids usually make short-term users sleepy. However,
long-term users develop tolerance and may suffer from insomnia.
In addition to alcohol and drugs that are abused, a variety of
prescription medications can affect sleep patterns. These
medications include antihistamines, corticosteroids, asthma
medicines, and drugs that affect the central nervous system.
Sleep disorders in children and adolescents
Pediatricians estimate that 20-30% of children have difficulties
with sleep that are serious enough to disturb their families.
Although sleepwalking and night terror disorder occur more
frequently in children than in adults, children can also suffer from
narcolepsy and sleep apnea syndrome. |
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