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Sleep apnea is a serious disorder in which breathing repeatedly stops long enough to disrupt sleep and often temporarily decrease the amount of oxygen and increase the amount of carbon dioxide in the blood.
People with sleep apnea often are very sleepy during the day, snore loudly, and have episodes of gasping or choking, pauses in breathing, and sudden awakenings with a snort.
Although the diagnosis of sleep apnea is in part based on symptoms, doctors usually use polysomnography to confirm the diagnosis and determine the severity.
Continuous positive airway pressure, oral appliances fitted by dentists, and sometimes surgery can be used to treat sleep apnea.
There are three types of sleep apnea: obstructive sleep apnea, central sleep apnea, and a mixed type.
Obstructive sleep apnea, the most common type, is caused by repeated closure of the throat or upper airway during sleep. This type of apnea affects about 2 to 9% of people in the United States. Obstructive sleep apnea is more common in obese people. Obstructive sleep apnea occurs when breathing is interrupted repeatedly during sleep for periods of more than 10 seconds. People have from 5 to 30 or more episodes of interrupted breathing per hour. Obesity, perhaps in combination with aging and other factors, leads to narrowing of the upper airway. Excessive use of alcohol and use of sedatives worsens obstructive sleep apnea. Having a narrow throat, thick neck, and round head—features that tend to run in families—increases the risk of sleep apnea. Hypothyroidism or excessive and abnormal growth due to excessive production of growth hormone (acromegaly) can contribute to obstructive sleep apnea. Sometimes a stroke can cause obstructive sleep apnea. In children, enlarged tonsils or adenoids, some dental conditions (such as a large overbite), and some birth defects (such as an abnormally small lower jaw) can cause obstructive sleep apnea.
Central sleep apnea, a much rarer type, is caused by a problem with the control of breathing in the brain (which is accomplished in the brain stem). Normally, the brain stem is very sensitive to changes in the blood level of carbon dioxide (a by-product of metabolism). When levels are high, the brain stem signals the respiratory muscles to breathe deeper and faster to remove carbon dioxide through exhalation, and vice versa. In central sleep apnea, the brain stem is less sensitive to changes in the carbon dioxide level. As a consequence, people who have central sleep apnea breathe less deeply and more slowly than normal. Using an opioid, a strong prescription pain reliever, can cause central sleep apnea. Being at high altitude can also cause central sleep apnea. A brain tumor is very rare cause. Unlike obstructive sleep apnea, central sleep apnea is not associated with obesity. In one form of central sleep apnea, called Ondine's curse, which usually occurs in newborns, people may breathe inadequately or not at all except when they are fully awake.
Mixed sleep apnea, the third type, is a combination of central and obstructive factors occurring in the same episode of sleep apnea. Episodes of mixed sleep apnea most often begin as obstructive apneas and are treated like obstructive apneas.
Symptoms during sleep are usually first noticed by a sleep partner, roommate, or housemate. In all types of sleep apnea, breathing may become abnormally slow and shallow, or breathing may suddenly stop (sometimes for up to 1 minute), then resume.
In obstructive sleep apnea, the most common symptom is snoring (see Snoring), but most people who snore do not have sleep apnea. In obstructive sleep apnea, snoring tends to be disruptive, with episodes of gasping or choking, pauses in breathing, and sudden awakenings with a snort. The person may awaken choking and frightened. In the morning, people are often not aware that have awoken many times during the night. When obstructive sleep apnea is severe, repeated bouts of sleep-related snorts and loud snores occur at night, and sleepiness or involuntary naps occur during the day. In people who live alone, daytime sleepiness may be the most noticeable symptom. Eventually, sleepiness interferes with daytime work and reduces the quality of life. For example, the person may fall asleep while watching television, while attending a meeting, or in more extreme sleepiness even while stopped at a red light when driving. Memory may be impaired, sex drive may be reduced, and interpersonal relationships suffer because the person is unable to participate actively in relationships due to sleepiness and irritability. In obstructive sleep apnea, the risk of stroke, heart attack, atrial fibrillation (an abnormal, irregular heart rhythm), and high blood pressure is increased. If middle-aged men have episodes of obstructive sleep apnea more frequently than about 30 per hour, the risk of premature death is increased.
People who are extremely obese can have obesity-hypoventilation syndrome (termed the Pickwickian syndrome) alone or in combination with obstructive sleep apnea. Excess body fat interferes with the movement of the chest, and excess body fat below the diaphragm compresses the lungs, which combine to cause shallow, less effective breathing. Excess body fat around the throat compresses the upper airway, reducing air flow. The control of breathing may be disordered, causing central sleep apnea.
Almost all affected children snore. Other sleep symptoms may include restless sleep and sweating at night. Daytime symptoms may include mouth breathing, morning headache, and problems concentrating. Learning and behavior problems are often common symptoms of obstructive sleep apnea in children. Children may also have growth delays. Excessive daytime sleepiness is less common than among adults with obstructive sleep apnea.
In central sleep apnea, snoring is not as prominent. However, the tempo of breathing is irregular and interrupted by pauses. Cheyne-Stokes respiration (periodic breathing) is one type of central apnea. In Cheyne-Stokes respiration, breathing gradually becomes more rapid, gradually slows down, stops for a short period, then starts again. Then the cycle repeats. Each cycle lasts 30 seconds to 2 minutes.
In all types of sleep apnea, the disturbances in sleep can result in daytime sleepiness, fatigue, irritability, headaches in the mornings, slowness of thought, and difficulty concentrating. Because oxygen levels in the blood may decrease significantly, atrial fibrillation may develop, and blood pressure may increase.
Prolonged, severe sleep apnea of any type increases the risk of heart failure and constriction of lung blood vessels. Then the heart cannot pump enough blood to the body, and the lungs cannot provide enough oxygen to or remove enough carbon dioxide from the body.
Sleep apnea is suspected on the basis of symptoms. The diagnosis is usually confirmed and severity is best determined in a sleep laboratory by using a test called polysomnography. In this test, electroencephalography (EEG—see page Tests for Brain, Spinal Cord, and Nerve Disorders : Electroencephalography) is used to monitor changes in levels of sleep and eye movements. The oxygen level in the blood is measured with an electrode placed on a finger or an earlobe (a procedure called oximetry). Airflow is measured with devices placed in front of the nostrils and mouth, and the motion and pattern of breathing are measured with a monitor placed on the chest. This evaluation can help doctors distinguish between obstructive and central sleep apnea.
Portable monitors used at home are being used more often to help diagnose sleep apnea. These monitors measure heart rate, level of oxygen in the blood, effort of breathing, position, and nasal airflow.
People with sleep apnea may be tested for complications, such as heart failure, high blood pressure, and atrial fibrillation. If doctors suspect central sleep apnea, testing may rarely be needed to determine the cause.
People should be warned of the risks of driving, operating heavy machinery, or engaging in other activities during which falling asleep would be hazardous. People who are undergoing surgery should inform their anesthesiologist that they have sleep apnea, because anesthesia can sometimes cause additional airway narrowing.
Support groups can provide information and help people with sleep apnea and their family members cope with the condition.
With treatment, the prognosis is usually excellent. Life span is not affected, and most serious complications can be prevented. Losing weight, quitting smoking, and not using alcohol excessively can help. Nasal infections and allergies should be treated. Hypothyroidism and acromegaly should be treated. Weight loss (bariatric) surgery frequently reduces sleep apnea and reverses symptoms in people who are very overweight (morbidly obese), but even people who lose a lot of weight as a result of surgery may not experience a significant decrease in sleep apnea symptoms.
Heavy snorers and people who often choke in their sleep should not consume alcohol or take sleep aids, sedating antihistamines, or other drugs that cause drowsiness. Sleeping on the side or elevating the head of the bed can help reduce snoring. Special devices strapped on the back help prevent people from sleeping on their back. The various other devices and sprays marketed to reduce snoring may help simple snoring, but they have not been shown to relieve obstructive sleep apnea. There are several surgical procedures marketed for snoring as well, but there is little proof of how well they work and how long they are effective.
People with obstructive sleep apnea, particularly those who have excessive daytime sleepiness, benefit most predictably from continuous positive airway pressure (CPAP). With CPAP, people breathe through a face or nose mask that provides a slightly higher pressure in the airway. This increased pressure props the throat open as the person breathes in. CPAP can be given with or without humidifying the delivered air. Close follow-up by a health care practitioner is needed during the first 2 weeks of use to ensure proper mask fit and provide appropriate encouragement as the person learns to sleep with the mask. Some people who use CPAP still have excessive daytime sleepiness. These people may benefit from taking modafinil.
Removable oral appliances, fitted by dentists, can help relieve obstructive sleep apnea (and snoring) in people with mild to moderate sleep apnea. These appliances, which are worn only while sleeping, help keep the airway open. Most appliances separate the jaws and push the lower jaw forward so the tongue cannot move backward to block the throat. Others hold the tongue forward.
Surgery of the head or neck as a treatment for sleep apnea is useful if there are enlarged tonsils or an obvious blockage of the upper airway by another structure. Surgery is sometimes used in people without obvious blockage if no other treatments have worked. The most common procedure is a uvulopalatopharyngoplasty, in which tissue from around the upper airways (for example, the tonsils and adenoids) is removed. It is most often helpful in people who have mild sleep apnea. Other surgical procedures are sometimes used, but they have not been studied as thoroughly. In children, removal of the adenoids and tonsils usually relieves sleep apnea.
The underlying disorder is treated if possible. For example, drugs may be given to reduce the severity of heart failure (see page Some Drugs Used to Treat Heart Failure). Otherwise, there are few, well-conducted clinical trials. Oxygen delivered by nasal prongs (not under pressure) may reduce episodes of apnea in people whose levels of blood oxygen become low while sleeping. Some people with central sleep apnea may benefit from CPAP. People with central apnea of the Cheyne-Stokes type have fewer episodes of apnea and a lower severity of heart failure with this treatment but do not survive longer. Acetazolamide can help people who have central sleep apnea caused by high altitude and possibly even people at sea level. Some people benefit from surgery to implant a device that stimulates the diaphragm (a diaphragmatic/phrenic nerve stimulator) to help the person breathe.
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