Sleep Disorders

Basics

Sleep disorders can manifest as an inability to sleep (insomnia), daytime sleepiness, abnormal movements or behavior during sleep, or an inability to sleep at the appropriate time. Insomnia, defined as a persistent difficulty falling or staying asleep that impairs daytime function, is the most common sleep complaint. Insomnia can be caused by a variety of conditions, and can take many forms.

People with daytime sleepiness are fatigued, have a tendency to fall asleep in inappropriate places at inappropriate times, and have poor concentration, among other problems.

Some people have abnormal behaviors during sleep that may manifest as leg jerking or other body movements. Common causes of this disorder include restless leg movement disorder, periodic limb movement disorder, or seizures.

Other disorders, related to sleep deprivation, result in sleepiness and an inability to fall asleep at appropriate times.

There are four different types of major sleep disorders: dyssomnias, parasomnias, those caused by medical, neurological, or psychiatric problems, and proposed sleep disorders, a category for which little information is currently available [Table 1]. Dyssomnias produce insomnia or excessive sleepiness as a result of either disturbed nighttime sleep or impaired wakefulness. The dyssomnias are a mix of disorders originating in different body systems, and are further divided into intrinsic, extrinsic, and circadian–rhythm sleep disorders. Intrinsic disorders such as narcolepsy, obstructive sleep apnea syndrome (OSAS), and restless legs syndrome (RLS) occur as a result of internal causes. Extrinsic dis-orders typically occur as a result of environmental factors. Circadian–rhythm disorders are a result of sleep–wake cycle disruption.

Parasomnias are undesirable phenomena, such as night terrors or sleepwalking, that occur during sleep. Parasomnias include rapid eye movement (REM)–related parasomnias that interfere with sleep, as well as disorders of arousal and sleep–wake transition.

Disorders associated with medical, psychiatric, and neurologic problems include conditions such as chronic obstructive pulmonary disease (COPD), anxiety disorders, alcoholism, and dementia.

Proposed sleep disorders comprise a category for cases in which there is not enough information to make a standard sleep disorder diagnosis. For example, it is not known whether short sleepers and long sleepers should be categorized as patients with sleep disorder, or if their time asleep merely represents an extreme in the range of normal sleep physiology.

Sleep disorders affect about one–third of the population. While individuals of all ages—even infants—can be affected, the elderly are especially prone to sleep disorders. Fortunately, most sleep disorders can be treated successfully through behavior modification and/or medication.

Causes

Medical or surgical problems, neurological disorders, and psychiatric disorders can all cause sleep disorders.

The numerous medical problems affecting sleep include asthma, heart disease, peptic ulcer disease, chronic obstructive pulmonary disease, and rheumatic disorders. Any sort of chronic pain may also impair sleep. Neurological disorders such as neurodegenerative diseases, strokes, headache syndromes, and neuromuscular disorders are associated with sleep disorders.

Psychiatric disorders such as depression, anxiety disorders, and panic attacks may be the underlying cause for approximately half of all cases of insomnia.

Drug and alcohol use can induce insomnia. Although some people use it to relax, alcohol, like other sedatives, disrupts sustained sleep. The nicotine found in cigarettes, as well as the caffeine in coffee, tea, and chocolate can also prevent you from falling asleep. In fact, for individuals sensitive to caffeine, even a few cups of coffee consumed in the morning can adversely affect sleep at night. Stimulant drugs such as amphetamines and antidepressants postpone sleep, as does phenylpropanolamine, which is present in many nonprescription decongestant treatments and diet aids.

Disruptions in internal sleep–wake cycles (circadian rhythm) can cause sleep disorders. Circadian rhythm refers to biologic changes throughout a 24–hour cycle. In mammals, nerve cell pacemakers control the biological rhythms involving the sleep–wake cycle.

Patients with circadian rhythm sleep disorders typically experience delayed–sleep phase syndrome, causing them to stay up well after midnight and wake up late in the morning. Delayed sleep phase syndrome is most commonly found in adolescents and young adults, and the onset of this disorder usually occurs around puberty.

Individuals with advanced–sleep phase syndrome retire early in the evening and awaken early in the morning.

Jet travel and night shift work contribute to circadian rhythm disruptions. Jet lag from rapid travel across time zones and shift–work sleep disorder are the most common circadian rhythm sleep disorders.

Stress and environmental factors can also lead to sleep problems. Stressful events related to financial problems, marital or family difficulties, or work demands are common causes of insomnia. For some patients, conditioning factors may cause sleep disruptions to persist even after the stressful event has passed.

Being at a high altitude alters breathing patterns, and thus can disturb sleep. People in this situation may awaken several times throughout the night, and will have poor–quality sleep. Although this sleep disturbance usually is worse during the first few nights spent at a high altitude, it may continue for a longer period of time.

Other factors, such as ventilation, humidity, noise, or an uncomfortable mattress can negatively affect sleep.