Synonyms of Apnea, Sleep
- Pediatric Obstructive Sleep Apnea
- Central Sleep Apnea
- Mixed Sleep Apnea
- Obstructive Sleep Apnea (Upper Airway Apnea)
- Pickwickian Syndrome
Sleep apnea is a sleep disorder characterized by temporary, recurrent interruptions of breathing (respiration) during sleep. Symptoms of this disorder include periodic wakefulness during the night, excessive sleepiness during the day, and loud snoring during sleep. People with this disorder are frequently overweight. Diagnosis and treatment of sleep apnea can avoid serious medical problems that may arise as a consequence of oxygen deprivation in untreated individuals. Sleep apnea occurs in three different forms: obstructive, central, and mixed.
An individual's rate of respiration is regulated by group of nerve cells in the brain that control the rhythm of breathing in response to changing oxygen levels in the blood (respiratory drive). In some apneas, the respiratory drive is abnormal. Obstructive sleep apnea (upper airway apnea) the most common form of sleep apnea, results from the blockage of the respiratory passages during sleep. Affected individuals may struggle to breathe and experience increased respiratory effort. Respiratory drive is unaffected in people with this form of sleep apnea but the blockage prevents them from breathing normally. Obstructive apnea is more likely than central apnea to be associated with snorting and arousal from sleep.
In the rare central sleep apnea, the brain does not send adequate signals to the diaphragm and lungs during sleep, resulting in low respiratory drive. In this form of sleep apnea, breathing stops and does not resume until the oxygen-deprived brain finally sends impulses to the diaphragm and lungs. In infants, central sleep apnea is defined as lasting 20 seconds or more.
Mixed sleep apnea is a combination of improper brain signals and obstruction of the respiratory passages. In some cases, sleep apnea is referred to as "Pickwickian Syndrome." In these cases, obstructive apnea is combined with obesity and an abnormally short neck. Infantile sleep apnea affects children less than one year old, and its cause is unknown. (For more information on infantile sleep apnea, see the Related Disorders section of this report.)
The most common symptoms of sleep apnea include excessive daytime sleepiness and loud snoring during the night. In obstructive apnea, labored breathing during sleep is interrupted by the narrowing (constriction) of airways. The episode ends when the muscles of the diaphragm and the chest build up sufficient pressure to force the airway open. Partial awakening then occurs, as the person gasps for air; sleep is resumed as breathing begins again. This cycle may be repeated many times during the night, and may lead to sleep deprivation. A person may wake in the morning feeling as if he/she has hardly slept.
If sleep apnea is not treated, various complications may occur. These include high blood pressure (hypertension), irregular heartbeats (arrhythmias), abnormal blood levels of oxygen and carbon dioxide, and swelling due to the accumulation of fluid in the arms and/or legs (peripheral edema). Other possible complications of untreated sleep apnea include heart disease and, brain damage due to lack of oxygen, sleepwalking, impotency, blackouts, automatic "robot-like" behavior, hallucinations, anxiety, irritability, and behaviors that are characteristic of sleep deprivation, such as memory loss. Affected individuals may also experience loss of interest in sex, morning headaches, and bedwetting.
Pediatric obstructive sleep apnea is characterized by snoring, difficulty breathing, excessive sleepiness and behavior problems. In some cases, it may be associated with developmental delays and growth failure.
Several physical conditions are often (but not always) associated with obstructive sleep apnea. These include obesity, a short thick neck, and reduction in muscle tone in the roof of the mouth (soft palate), the uvula, and the throat (pharynx). The upper airway may be narrowed by abnormally enlarged tonsils or adenoids, a deviated nasal septum, polyps in the nose, or congenital abnormalities. At high altitudes sleep disruption may occur because of the low oxygen concentration in the air.
Central apnea and the associated unstable respiratory control in the brain may be the result of an abnormally high partial pressure of carbon dioxide (portion of total blood gas pressure) in the blood. This form of sleep apnea may also be associated with a decrease in the rate of metabolism during sleep. Central sleep apnea may also be caused by lesions in the brain stem (primary respiratory neurons of the medulla) or in the spinal cord (descending cervical pathways) which control the rate of respiration (respiratory drive).
In some cases, obstructive sleep apnea is thought to be inherited as an autosomal dominant genetic trait. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.
Sleep apnea is a common sleep disorder that affects approximately 2.5 million people in the United States. Males are affected by this disorder more often than females. The prevalence of the obstructive form of sleep apnea is estimated to be about 2 to 2.5 percent in females and approximately 4 percent in males. Many individuals affected by sleep apnea are at least 20 percent above ideal body weight. Not all affected individuals are overweight. Overweight men over the age of 40 are most likely to develop sleep apnea, however, it may occur at any age, even during childhood. Most people with sleep apnea are not properly diagnosed and they tend to blame their chronic tiredness on other lifestyle factors.
Recent studies indicate that approximately two percent of women and four percent of men in the middle-age work force meet the minimal criteria for sleep apnea. Both men and women who snore habitually tend to have a higher incidence of sleep apnea. It is felt that the occurrence of undiagnosed sleep apnea is high among men and much higher than previously thought in women. According to one study, pediatric obstructive sleep apnea occurs in approximately 2 percent of children. However, it is also believed to be underdiagnosed.
Symptoms of the following disorders can be similar to those of sleep apnea. Comparisons may be useful for a differential diagnosis:
Narcolepsy is a rare neurological sleep disorder characterized by excessive drowsiness during the day, and the inability to resist sleep. Sleep attacks, called cataplexy, can include extreme muscle weakness, hallucinations, and paralysis while sleeping. The symptoms of this disorder typically begin between the ages of 10 and 20 years and symptoms vary greatly from patient to patient. Exaggerated daytime drowsiness is usually the first symptom of Narcolepsy. Sleep attacks can be triggered by extreme emotions such as laughing or surprises, or quiet environments such as listening to a lecture or television. (For more information on this disorder, choose "Narcolepsy" as your search term in the Rare Disease Database.)
Congenital Central Hypoventilation Syndrome is a rare neurological disorder characterized by the dysfunction of that portion of the brain that regulates respiration. The disorder typically affects infants, but may also occur in adolescents and adults. The primary symptom of Congenital Central Hypoventilation Syndrome is an abnormally slow rate of respiration while sleeping (nocturnal hypoventilation). (For more information on this disorder, choose "Central Hypoventilation" as your search term in the Rare Disease Database.)
Infantile sleep apnea is a neurological disorder of infancy characterized by the temporary cessation of breathing as a result of the abnormal function of the area of the brain that controls respiration. Infantile apnea is defined as an apnea occurring in children less than 1 year old. Infants with this disorder stop breathing temporarily which can result in low levels of oxygen in the blood and an abnormally slow heartbeat. (For more information on this disorder, choose "infantile apnea" as your search term in the Rare Disease Database.)
Chronic daytime tiredness and loud snoring with periodic gasping for breath during the night should be a warning sign that evaluation at a sleep disorders clinic is warranted. Diagnosis of sleep apnea requires evaluation at a sleep disorder center where overnight testing for at least one night, or daytime sleep tests that monitor respiration, can be performed. (See Association of Sleep Disorder Centers in the Resources section of this report.) Nocturnal polysomnography or nocturnal oximetry may be used to confirm a suspected diagnosis of pediatric obstructive sleep apnea.
Treatment of mild cases of obstructive sleep apnea usually consists of sleeping in a recliner chair, or elevating the bed's headposts by 6 to 8 inches. Elevation of the head can keep the tongue from falling backward and blocking the upper airway if the tongue causes the obstruction. In some cases, drugs may be used to stimulate breathing including theophylline, tricyclic antidepressants such as protriptyline and clomipramine, central nervous system stimulants such as pemoline or tranquilizers such as thioridazine. The drug nicotine initially stimulates nerve impulses and subsequently (in high doses), inhibits nerve impulses.
Some people are diagnosed with positional sleep apnea that occurs while sleeping in certain positions (e.g., on their backs) that cause a breathing obstruction. Sewing a bulky object in the back of the sleeping garment can make sleeping on the back (supine) so uncomfortable that the person turns over and instinctively avoids sleeping in the position. This may help to clear the obstruction to the airway that occurs as a result of positional sleep apnea.
Individuals with either central or obstructive sleep apnea that is not caused by a sleeping position are treated with a medical device called Continuous Positive Airway Pressure (CPAP). At night an affected individual's nose is connected through a tube to the CPAP machine, which is about the size of a small television. This device forces air through the tube at low pressure, just sufficient to keep the individual's upper airway open and permit air to enter the lungs. It is designed not to harm the user should it malfunction or the power fail. The pressure is set to fit an individual's own breathing pattern as determined by sleep testing. The device must be prescribed by a doctor. Approximately 85% of individuals with obstructive sleep apnea are helped with this type of device; oxygen levels return to normal and excessive daytime sleepiness disappears.
A surgical technique that is sometimes used for people who do not adjust to the CPAP device is uvulo-palato-pharyngoplasty (UPPP). Loose tissues are tightened in the back of the mouth and top of the throat, and excess tissues that block the airway in those areas are trimmed away. UPPP has been helpful in about 55 percent of individuals with obstructive sleep apnea who have undergone this surgery.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
Currently (2007) there is great investigational interest in this condition. This is evidenced by the more than 60 clinical trials for sleep apnea listed on www.clinicaltrials.gov. These trials deal with a wide range of topics and are concerned with treatment, diagnoses, and the effects of this condition.
Apnea, Sleep Resources
NORD Member Organizations:
(To become a member of NORD, an organization must meet established criteria and be approved by the NORD Board of Directors. If you're interested in becoming a member, please contact Susan Olivo, Membership Manager, at email@example.com.)
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FROM THE INTERNET
McKusick VA., ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No:107650; Last Update: 4/30/99.
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