Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Sleep Apnea


Kingman P. Strohl

, MD, Case School of Medicine, Case Western Reserve University

Reviewed/Revised Oct 2022
Topic Resources

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.

  • Sleep apnea increases the risk of certain medical disorders and premature death.

  • Although the diagnosis of sleep apnea is in part based on a doctor's evaluation of 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.

Sleep apnea is a very common problem. Over 1 billion people are affected worldwide. There are different types of sleep apnea with different causes and risk factors.

Types of Sleep Apnea

There are two types of sleep apnea:

  • Obstructive sleep apnea

  • Central sleep apnea

Some people have a combination of obstructive and central sleep apnea.

Sleep Apnea

Did You Know...

  • People who have excessive daytime sleepiness and who snore should discuss these symptoms with their doctor.

Obstructive sleep apnea

Obstructive sleep apnea, the most common type of sleep apnea, is caused by repeated closure of the throat or upper airway during sleep. The upper airway includes the passageway from mouth and nostrils to throat and down to voice box, and these structures may change position as a person breathes.

This type of apnea affects the health and well being of about 8 to 16% of adults. Obstructive sleep apnea is more common in people with obesity.

Doctors diagnose obstructive sleep apnea when the following occur:

  • Breathing is interrupted during sleep

  • There are 5 or more breathing interruptions per hour

  • Each interruption lasts for more than 10 seconds

Many risk factors increase the likelihood of obstructive sleep apnea. Obesity Obesity Obesity is a chronic, recurring complex disorder characterized by excess body weight. Obesity is influenced by a combination of factors that includes genetics, hormones, behavior, and the environment... read more Obesity , perhaps in combination with aging and other factors, leads to narrowing of the upper airway. Excessive use of alcohol and use of sedatives worsen 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. Low levels of thyroid hormone (hypothyroidism Hypothyroidism Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more Hypothyroidism ), having gastroesophageal reflux disease (GERD) Gastroesophageal Reflux Disease (GERD) In gastroesophageal reflux disease, stomach contents, including acid and bile, flow backward from the stomach into the esophagus, causing inflammation in the esophagus and pain in the bottom... read more Gastroesophageal Reflux Disease (GERD) or angina Angina Angina is temporary chest pain or a sensation of pressure that occurs while the heart muscle is not receiving enough oxygen. A person with angina usually has discomfort or pressure beneath the... read more at night, or excessive and abnormal growth due to excessive production of growth hormone (acromegaly Gigantism and Acromegaly Overproduction of growth hormone causes excessive growth. In children, the condition is called gigantism. In adults, it is called acromegaly. Excessive growth hormone is almost always caused... read more Gigantism and Acromegaly ) can contribute to obstructive sleep apnea. Sometimes a stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more can cause obstructive sleep apnea. Sleep apnea tends to run in families, so there may be a genetic risk.

Did You Know...

  • People with obstructive sleep apnea should avoid alcohol and sedating drugs, particularly before bedtime.

Obstructive sleep apnea in children

Most affected children snore. Other sleep symptoms may include restless sleep and sweating at night. Some children wet the bed. Daytime symptoms may include mouth breathing, morning headache, and problems concentrating. Learning and some behavior problems (such as hyperactivity) are often common symptoms of severe obstructive sleep apnea in children. Children may also have growth delays. Excessive daytime sleepiness is less common in children than among adults with obstructive sleep apnea.

Central sleep apnea

Central sleep apnea is rare, compared to obstructive sleep apnea. It is caused by a problem with the control of breathing in the part of the brain called the brain stem. Normally, the brain stem is very sensitive to changes in the blood level of carbon dioxide (a by-product of the body's normal chemical reactions). When carbon dioxide 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 does not respond appropriately to changes in the carbon dioxide level. As a consequence, during sleep, people who have central sleep apnea may have pauses in their breathing or may breathe less deeply and more slowly than normal.

There are many reasons why the brain stem may not send out appropriate breathing signals. For example, a stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more , brain infection (encephalitis Encephalitis Encephalitis is inflammation of the brain that occurs when a virus directly infects the brain or when a virus, vaccine, or something else triggers inflammation. The spinal cord may also be involved... read more ), or birth defect of the brain may affect the brain stem. Opioids used for pain relief and a number of other drugs can cause central sleep apnea. Being at high altitude can also cause central sleep apnea. Central sleep apnea can occur in people with heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more Heart Failure (HF) . A brain tumor is a very rare cause. Unlike obstructive sleep apnea, central sleep apnea is not caused by obesity.

In one form of central sleep apnea, called Ondine curse, which usually occurs in newborns, people may breathe inadequately or not at all except when they are fully awake. Ondine curse can be fatal.

Symptoms of Sleep Apnea

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 all types of sleep apnea, the disturbances in sleep can result in daytime sleepiness Insomnia and Excessive Daytime Sleepiness (EDS) The most commonly reported sleep-related problems are insomnia and excessive daytime sleepiness. Insomnia is difficulty falling asleep or staying asleep, waking up early, or a disturbance in... read more , fatigue, irritability, headaches in the mornings, slowness of thought, and difficulty concentrating. People who have excessive sleepiness are at increased risk of injury when operating motor vehicles or heavy machinery or doing other activities during which it is dangerous to be sleepy. They may have difficulties at work and sexual dysfunction. Because oxygen levels in the blood may decrease significantly, atrial fibrillation Atrial Fibrillation and Atrial Flutter Atrial fibrillation and atrial flutter are very fast electrical discharge patterns that make the atria (upper chambers of the heart) contract very rapidly, with some of the electrical impulses... read more may develop, and blood pressure may increase.

Obstructive sleep apnea

In obstructive sleep apnea, the most common symptom is snoring Snoring Snoring is a raspy noise produced in the nose and throat during sleep. It is quite common and becomes more common as people age. About 57% of men and 40% of women snore. However, what qualifies... read more , 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. Some people wake with a sore throat or a dry mouth. 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.

People may have difficulty staying asleep.

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 people with sleep apnea who live with others, their noisy, restless sleep may adversely affect their relationships with bed partners, roommates, and/or housemates.

Did You Know...

  • Only a few people who snore have obstructive sleep apnea, but most people who have obstructive sleep apnea snore.

Central sleep apnea

In central sleep apnea, snoring is not as prominent. 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.

Obesity-hypoventilation syndrome

People with extreme obesity can have obesity-hypoventilation syndrome (termed the Pickwickian syndrome) alone or in combination with obstructive sleep apnea. In obesity-hypoventilation syndrome, 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.

Diagnosis of Sleep Apnea

  • Doctor's evaluation

  • Polysomnography

Sleep apnea is suspected on the basis of the person's symptoms. Sometimes doctors use questionnaires to help screen for symptoms, such as excessive daytime sleepiness, which may be due to obstructive sleep apnea. The diagnosis is usually confirmed and severity is best determined by monitoring the person's breathing during sleep. The first step is usually monitoring at home with portable equipment that the person wears for several nights. This equipment can monitor breathing, heart rate, airflow through the nose, and oxygen levels. A more thorough test can be done using a polysomnography, during which the person sleeps overnight in a sleep laboratory. This evaluation can help doctors distinguish between obstructive and central sleep apnea.

In polysomnography:

The sleep tests determine the apnea-hypopnea index (AHI). The AHI represents the average number of episodes of nonbreathing (apnea) and decreased breathing (hypopnea) occurring per hour of sleep time. The more events that occur, the more severe the sleep apnea and the greater the likelihood of adverse effects. Doctors use the AHI plus the person's symptoms to diagnose sleep apnea.

Sometimes additional testing is needed to help doctors determine the cause. People with sleep apnea may be tested for complications, such as high blood pressure and atrial fibrillation. If doctors suspect central sleep apnea, testing may rarely be needed to determine the cause.

Treatment of Sleep Apnea

  • Control of risk factors

  • Continuous positive airway pressure or mouth guards or other devices fitted by a dentist

  • Possibly airway surgery or electrical stimulation of the upper airway

Treatment is directed at both risk factors and sleep apnea itself.

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.

Obstructive sleep apnea

If people are prescribed treatment and they follow that treatment, the prognosis is usually excellent. Life span is not affected, and most serious complications can be prevented. Blood pressure usually drops a few points.

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 is helpful but can be very difficult, particularly for people who are sleepy and fatigued. Thus, weight-loss (bariatric) surgery is often recommended for people who are very overweight (have severe obesity). In such people, bariatric surgery reduces sleep apnea and reverses symptoms in about 85% of people.

Heavy snorers and people who often choke in their sleep should not consume alcohol or take sleep aids, sedating antihistamines, or other medications 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.

Continuous positive airway pressure (CPAP) is the main treatment for people with obstructive sleep apnea, particularly those who have excessive daytime sleepiness. With CPAP, people breathe through a face or nose mask connected to a device 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. If a person has a deviated nasal septum, doctors may recommend surgery to repair the deviated septum (septoplasty) because repair may make CPAP treatment more successful.

However, many people find CPAP hard to tolerate and so they stop using it or use it only sometimes. If doctors and technicians help people find a device that fits them properly and encourage them, people are more likely to have long-term success with CPAP.

Some people who use CPAP still have excessive daytime sleepiness. These people may benefit from taking a mild stimulant used to treat daytime sleepiness in people with obstructive sleep apnea (for example, modafinil or solriamfetol). Other medications are also being tested for people with obstructive sleep apnea.

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 consist of two pieces of plastic molded to the shape of the upper and lower teeth. The two pieces link together and are designed to pull the lower jaw forward so the tongue cannot move backward to block the throat.

Because snoring is common and troubles some and because CPAP use can be difficult, some alternative devices that have not been thoroughly studied are marketed and sold directly to consumers. Prior to starting any treatment plan, people should discuss their treatment options with a health care provider.

Upper airway stimulation is a procedure in which an implanted electrical device is used to stimulate one of the cranial nerves Overview of the Cranial Nerves Twelve pairs of nerves—the cranial nerves—lead directly from the brain to various parts of the head, neck, and trunk. Some of the cranial nerves are involved in the special senses (such as seeing... read more that controls the tongue (the hypoglossal nerve). Stimulating this nerve activates muscles that push the tongue forward and help keep the airway open. This therapy can be successful in some people with moderate to severe obstructive sleep apnea who are unable to tolerate CPAP therapy.

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. In children, surgery to remove the tonsils and adenoids is the most common treatment (called adenoidectomy). This type of surgery usually relieves sleep apnea, particularly if the tonsils or adenoids are enlarged. Surgery is sometimes used in people without obvious blockage if no other treatments have worked.

Uvulopalatopharyngoplasty is a surgical procedure that opens the upper airway by removing some tissue from the upper airways (for example, from the palate, uvula, tonsils, and adenoids). It is most often helpful in people who have mild sleep apnea. However, this procedure has been largely replaced by less aggressive approaches that, for example, attempt to stabilize the walls of the pharynx (the cavity behind the nose and mouth). Other surgical procedures are sometimes used, but they have not been studied as thoroughly for predictability and durability.

Tracheostomy (making a permanent opening in the windpipe to insert a breathing tube) is the most effective treatment for obstructive sleep apnea. However, tracheostomy is done only as a last resort for people with the worst disease who have not responded to other treatments.

Central sleep apnea

In people with central sleep apnea, the underlying disorder is treated if possible. For example, medications may be given to reduce the severity of heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more Heart Failure (HF) . People also are advised to avoid or reduce alcohol and any drugs that worsen the sleep apnea. 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 low levels of CPAP. People with central apnea of the Cheyne-Stokes type have fewer episodes of apnea and better heart function with this treatment but do not survive longer.

People who have central sleep apnea caused by high altitude, and some who have heart failure, may benefit from the drug acetazolamide.

Some people benefit from a procedure to implant a device that stimulates the nerves controlling the diaphragm (a diaphragmatic/phrenic nerve stimulator) to help the person breathe.

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Diamox, Diamox Sequels
quiz link

Test your knowledge

Take a Quiz!