Sleep Apnea

Table of Contents

The symptoms are common. Snoring. Daytime sleepiness. Repeated awakening during the night. Weight gain. The feeling of gasping and choking.

These are some of the symptoms of sleep apnea, one of the most common and potentially damaging sleep disorders. It is also one of the most treatable. Sleep apnea affects more than 18 million adults in the US, and 100 million worldwide.

Like many sleep disorders, sleep apnea is underdiagnosed. (1) Only in the last thirty years have the health effects of the disorder — and the urgent need to treat it — become clear.

Note: The content on Sleepopolis is meant to be informative in nature, but it shouldn’t take the place of medical advice and supervision from a trained professional. If you feel you may be suffering from any sleep disorder or medical condition, please see your healthcare provider immediately.

What is Sleep Apnea?

Sleep apnea is a pause in breathing during sleep. Breathing typically stops for at least ten seconds, and may stop a hundred or more times each hour. An episode of stopped breathing is referred to as an apnea. Each apnea must last at least ten seconds to have an impact on the oxygenation of the blood. (2)


To be considered sleep apnea, pauses in breathing must occur at least five times each hour. The disorder is categorized as mild, moderate, or severe depending on the frequency and length of pauses in breathing.

  • Mild sleep apnea: 5 to 15 episodes per hour
  • Moderate sleep apnea: 15 to 30 episodes per hour
  • Severe sleep apnea: more than 30 episodes per hour

Severe sleep apnea is the most dangerous form, and is associated with weight gain, an elevated risk of cardiovascular disease, and long-term sleep debt. (3) Even mild and moderate sleep apnea have physical and cognitive repercussions, including daytime sleepiness and dysfunction of the metabolism.


From the Greek word apnous, meaning breathless.

Sleep Apnea Symptoms

Consistent snoring is the most common symptom of sleep apnea. Though snoring is often dismissed as a natural part of sleeping, it indicates a structural or cognitive problem that may result in serious health consequences.

In addition to snoring, there are numerous other symptoms of sleep apnea. These include:

  • Gasping, choking, or feeling short of breath during sleep
  • Daytime sleepiness
  • Waking with a dry throat or mouth
  • Feeling restless during sleep
  • Frequent waking at night, including visits to the bathroom
  • Headaches upon waking

Other less common symptoms of sleep apnea include acid reflux that occurs overnight, feeling hot, or perspiring excessively during sleep. In addition to symptoms directly related to apnea events, the disorder can cause the full range of sleep debt symptoms, which include:

  • An increased risk of accidents, injuries, and falling asleep while driving
  • Metabolic dysfunction
  • Stroke
  • Heart attack
  • Obesity

These conditions occur due to the hypoxia characteristic of sleep apnea, as well as insufficient and fragmented sleep. (4Lack of oxygen may cause chronic inflammation that leads to the cardiovascular effects seen in severe or long-term sleep apnea.

Sleep apnea-related obesity is caused by metabolic dysfunction, which increases fat storage, levels of the hunger hormone ghrelin, and the risk of diabetes. Once sleep apnea is treated, metabolism and appetite hormones often regulate, reducing simple carbohydrate cravings and balancing the body’s fat storage mechanism.


Q: What is hypoxia? A: The condition that results when the body or part of the body is deprived of oxygen.

What Causes Sleep Apnea?

Most people think of sleep apnea as a disorder with a single cause, but there are three types of sleep apnea, each occurring due to different physical processes. A sleep study can help determine the type and severity of the apnea, as well as the best options for treatment.

Obstructive sleep apnea, or OSA. OSA is the most common type of sleep apnea, with cases rising rapidly. (5) The disorder is caused by obstruction of the airway by the tongue or soft tissues of the palate or throat. The muscles of the throat relax during sleep, and may allow the tongue to fall into the back of the throat. The flow of air is restricted, causing snoring and preventing adequate oxygen from reaching the brain.

The risk of obstructive sleep apnea increases in men over 50 who smoke or have high blood pressure. A family history of sleep apnea also raises the risk, as does being black, Hispanic, or from the Pacific islands. A neck circumference of over 15.75 inches is more likely to be associated with sleep apnea, particularly if BMI is high. (6)

Anatomical features such as a smaller jaw can contribute to sleep apnea, as can excessive weight around the neck. Enlarged tonsils, allergies, and other causes of nasal congestion may increase the risk of airway obstruction. Sleep position — particularly lying on the back — can have a significant role in obstructive sleep apnea.

Central sleep apnea. Central sleep apnea is caused by a failure of the brain to send the proper signals to the muscles that control breathing. (7) Central sleep apnea is much less common than obstructive sleep apnea, and is typically a result of a serious medical condition such as stroke, kidney failure, or spinal cord injury. Use of certain medications, alcohol, or recreational substances may also contribute to central sleep apnea.

Complex sleep apnea. Complex sleep apnea is a combination of central and obstructive sleep apnea. (8) Complex sleep apnea may result from congestive heart failure and other medical conditions, as well as medication use. Narcotic pain medications are particularly associated with central and complex sleep apnea.

Congestive heart failure

A cardiac condition involving weakness and/or stiffness of the heart muscle. This type of heart failure is usually the result of such conditions as coronary artery disease and high blood pressure.

Diagnosing Sleep Apnea

There are no sleep apnea tests that take the place of a sleep study. Both home and laboratory sleep studies measure the apnea-hypopnea index, or AHI. An AHI of five or above is indicative of sleep apnea. Because sleep apnea may be worse or better depending on body position, home and lab sleep studies measure AHI while the body is in various positions during sleep.

The AHI score determines the degree of sleep apnea, and is categorized as follows:

  • mild sleep apnea — 5-14.9
  • moderate sleep apnea — AHI 15-29.9
  • severe sleep apnea —  AHI ≥30

As demand for diagnosis of sleep apnea and other sleep disorders has grown, the need for a more convenient and cost-effective method of diagnosis has increased, as well. The use of home sleep studies is becoming more common, and more accepted by physicians as an alternative means of diagnosis. (9)


Q: What does apnea-hypopnea mean? A: Apnea is the number of pauses in breathing, while hypopnea refers to the number of slow or shallow breaths.

A home sleep study typically arrives in the mail, is conducted at home, and then is sent back to the sleep study company to interpret. Results are usually sent to the doctor, who explains them to the patient. Some sleep study companies offer a post-study telephone or internet consultation with a sleep specialist. The specialist may discuss test results and prescribe treatment, which might include a dental device, CPAP machine, or surgery.

Home sleep studies usually include three types of sensors: a machine strapped around the chest, a pulse oximetry device that measures oxygen saturation, and a sensor worn in the nose to measure breathing and oxygen levels.

The home study recording device is light, usually about 3 ounces, and is strapped to the chest belt. An accurate diagnosis requires at least four hours of sleep while connected to the sleep study machine.

Though home sleep studies are becoming increasingly popular, the gold standard for diagnosing sleep apnea is a study in a laboratory specializing in sleep disorders. (10) A laboratory study requires spending a full night away from home. (11) Also known as a polysomnogram, a laboratory study records the following information during sleep:

  • Brain waves
  • Heart rate
  • Breathing
  • Eye movements
  • Limb movements
  • Oxygen levels in the blood

Some doctors may also ask for what’s known as a “split-night” lab study, which involves a typical sleep study for several hours followed by a study of the patient while connected to a CPAP machine.

What Happens During Sleep Apnea?


An apnea occurs when the tongue or soft tissues block the airway during sleep, or when the brain fails to send the proper signals to the muscles that control breathing. During obstructive sleep apnea, the throat or airway muscles relax, allowing the tongue to block the throat. This causes a pause in breathing that may last longer than ten seconds, and result in snoring, gasping, and/or choking.

Inadequate oxygen during an apnea event signals the brain to wake up so that breathing can start again. This may cause full awakening, or change the stage of sleep to a lighter, less restorative phase. Sleep apnea events tend to occur most frequently during REM sleep.

When breathing is obstructed, the muscles of the diaphragm and chest increase their effort to inhale. This can cause gasping and choking, and for the apnea sufferer awakened from sleep, a feeling of suffocating. In an effort to receive sufficient oxygen, the brain causes a full or partial awakening. If sleep apnea is severe, this may happen dozens of time each night.

REM sleep

The stage of sleep when brain activity is most similar to being awake. Dreams are most vivid during REM sleep, and muscles are paralyzed to prevent the acting out of dreams.

The Physical and Cognitive Effects of Sleep Apnea

The lack of oxygen and deep, restorative sleep can have a significant effect on the physical and mental functioning of sleep apnea sufferers. (12) Cognitive effects of sleep apnea can include:

  • Mood changes, including irritability, depression, and anxiety
  • Memory deficits
  • High blood pressure
  • Difficulties with concentration and learning
  • Decreased reaction times
  • Trouble controlling emotional responses

Research suggests that people with sleep apnea have trouble converting short-term memories into long-term ones. This may be due to repeated interruptions to the processing and storing of memories that take place during sleep.

Sleep apnea not only starves the brain of oxygen, it changes the brain’s shape. Research shows that sleep apnea can cause shrinkage of parts of the brain that store episodic memories. (13) Episodic memories refer to the recollection of times, places, and people, or “who, what, when, where, and why” knowledge.

Areas of gray and white brain matter are also smaller in sleep apnea sufferers. This damage may be the cause of the poor memory, emotional impacts, and learning difficulties seen in people who experience chronic breathing difficulties during sleep. CPAP therapy appears to reverse the damage sleep apnea causes to these parts of the brain. (14)


Another potential complication of sleep apnea is atrial fibrillation, one of the most common cardiac arrhythmias. Both sleep apnea and atrial fibrillation are associated with higher risk of stroke and premature death. (15) Sleep apnea may contribute to atrial fibrillation through increased strain on parts of the heart, particularly in an obese person. Atrial fibrillation is particularly common in later life, when sleep apnea is more likely to occur.

Recent research has found an association between sleep apnea and a deadly blood cancer called multiple myeloma. (16) Sleep apnea appears to drive certain cancers or make them more aggressive through its detrimental effect on immunity and other essential physical functions.

Sleep Apnea in Children

Sleep apnea diagnoses in children are increasing due in part to increasing levels of obesity. Known as pediatric obstructive sleep apnea, the disorder is nearly always a result of a blockage of the airway.

Unlike symptoms in adults, symptoms of pediatric sleep apnea are less likely to include daytime sleepiness. Children can display warning signs during sleep and waking hours. Symptoms during sleep may include:

  • Snoring
  • Pauses in breathing
  • Restless sleep
  • Snorting, coughing or choking
  • Mouth breathing
  • Bed wetting
  • Night terrors

Common warning signs of pediatric sleep apnea during wakefulness include:

  • Poor academic performance
  • Difficulties with learning and concentration
  • Weight gain
  • Hyperactivity and other behavioral issues

The most common cause of sleep apnea in children is enlargement of the tonsils and adenoids, the lymphatic tissue behind the nasal cavity. (17) Removal of the tonsils and other obstructive tissue may eliminate the disorder in children. If obesity is the cause, weight loss of at least 10% of body weight can improve or eliminate symptoms.


Q: How many children are affected by pediatric sleep apnea? A: Approximately 2-4%, with peak ages between 2 and 8 years old when tonsils tend to enlarge, and adolescence due to weight gain.

Sleep Apnea Treatment

Treatment of sleep apnea is crucial to preventing the detrimental physical and mental impacts that often result from the disorder. Treatments are varied, and depend on the type and severity of the disorder, as well as the tolerance of the patient.


CPAP, or sleep apnea machine

The most common treatment for sleep apnea involves a CPAP machine, or continuous positive airway pressure device. A CPAP applies gentle air pressure into the blocked airway, allowing oxygen to enter the lungs. (18)

CPAP can help reduce some of the most serious effects of hypoxia and sleep debt by providing sufficient oxygen to the body and improving the quality and duration of sleep. (19) Most CPAP machines use a nasal mask attached to a hose, which then attaches to the machine itself. Some CPAP machines include a built-in humidifier, as well. Machines come in full sizes, and smaller sizes for use while traveling.

Sleep specialists typically recommend that the CPAP machine be used at all times during sleep, including naps. Wearing the CPAP machine may take an adjustment, and a doctor may need to correct the pressure settings.

Benefits of a CPAP vs. other types of other sleep apnea treatment include the following:

  • CPAP is the “gold standard” of sleep apnea treatment
  • The machines are typically covered by insurance
  • The CPAP is appropriate for moderate to severe sleep apnea, which oral devices may not be able to correct
  • Also available in smaller sizes for travel
  • Many different models to choose from

Oral Appliances

Oral appliances for sleep apnea fit like a mouth guard, and work by pulling the jaw and tongue forward and opening the airway. (20) They are typically not prescribed for people with severe sleep apnea, but may be an option for those diagnosed with mild to moderate OSA.

Oral appliances are typically fitted by dentists who specialize in dental devices for sleep apnea. These devices are custom-made for the needs and anatomy of each individual. A number of oral appliances are available without a custom fitting at a significantly lower cost, but may not correct sleep apnea due to their “one size fits all” approach.

Dental sleep medicine practitioner

A dentist who specializes in treating sleep apnea using oral appliances.

Because some off-the-shelf oral devices are bulky and don’t fit in the mouth the way custom-fit devices do, they can worsen sleep apnea by blocking the airway further. Sleep specialists typically recommend a device that is custom fitted by a dentist instead of one that is not custom-fitted, and has limited scientific research behind it. Custom-fit devices may require a period of titration, or adjustment, to maximize comfort and effectiveness.

Benefits of oral appliances compared to CPAP include:

  • Better compliance vs. other apnea treatments
  • Quiet. A CPAP machine requires electricity to run its motor, which may be disruptive to sleep depending on brand. An oral device is silent
  • Small and portable
  • When the mouth is closed, the device is not visible to a bed partner
  • May require less adjustment time


CPAP and oral appliances are generally the first line of treatment for sleep apnea. Surgery may be recommended for sleep apnea sufferers who can’t tolerate the CPAP machine or dental devices, or for whom these treatments are ineffective. (20)

Nasal Surgery. Nasal obstruction and congestion can cause or worsen sleep apnea. Surgery may be performed to correct nasal abnormalities or open the airway. Most nasal surgery to improve sleep apnea involves straightening the septum between nasal passages and reducing the size of the turbinates, the structures that help humidify and clean the nose. Smaller turbinates and a straightened septum may allow more room for breathing, reducing the risk of apnea events.

Jaw Surgery. Jaw surgery, or maxillomandibular advancement, may be recommended if sleep apnea is caused or worsened by anatomical features that make airway obstruction more likely. Because jaw surgery can be complex and require considerable recovery time, it is often a treatment of last resort. It may be helpful to sleep apnea sufferers with a small jaw, as this facial feature can allow the tongue to more easily drop back into the throat and block the airway during sleep.

UPPP Surgery. A uvulopalatopharyngoplasty, or UPPP, is one of the most frequently performed surgeries for sleep apnea, with approximately 33.000 patients undergoing the procedure each year. During a UPPP, the surgeon removes excess tissue from the pharynx and soft palate. This part of the mouth and throat is called the oropharynx.

UPPP surgery can reduce or eliminate the vibration of the soft palate and pharnyx, which causes snoring and narrows the size of the airway. The surgery requires an overnight stay in the hospital, as the recovery can be painful for up to one week.  Patients who suffer from snoring gain a great deal of improvement from this procedure, as snoring is often due to the reverberation of the soft palate against the back wall of the pharynx.

Tongue Surgery. Tongue surgery may be recommended for sleep apnea sufferers with excessive tissue at the back of the tongue. This tissue can block the airway during sleep, making breathing difficult, particularly when lying on the back.

Bariatric Surgery. Bariatric surgery for weight loss can improve or eliminate sleep apnea once BMI decreases. This is typically a surgery of last resort, unless the patient desires it for purposes of weight loss in addition to sleep apnea treatment.


Medications are not typically recommended for treating sleep apnea. Though the narcolepsy medication Modafinil may be used to treat daytime sleepiness in sleep apnea sufferers, most specialists prefer to improve sleepiness and other symptoms by treating the underlying causes of the disorder itself.

Last Word From Sleepopolis

Though all sleep disorders have effects on the body and cognitive function, sleep apnea is one of the most potentially harmful. Experts believe that  4% of men and 2% of women suffer from sleep apnea, though these numbers are likely to be low.

Despite common and easily recognizable symptoms, many cases of sleep apnea go untreated or undiagnosed. The disorder is a frequently overlooked cause of such health conditions as cardiovascular disease, diabetes, and obesity. Recognizing the signs of sleep apnea and seeking a diagnosis are important steps toward successfully treating this serious disorder.


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Rose MacDowell

Rose is the former Chief Research Officer at Sleepopolis. An incurable night owl, she loves discovering the latest information about sleep and how to get (lots) more of it. She is a published novelist who has written everything from an article about cheese factories to clock-in instructions for assembly line workers in Belgium. One of her favorite parts of her job is connecting with the best sleep experts in the industry and utilizing their wealth of knowledge in the pieces she writes. She enjoys creating engaging articles that make a difference in people’s lives. Her writing has been reviewed by The Boston Globe, Cosmopolitan, and the Associated Press, and received a starred review in Publishers Weekly. When she isn’t musing about sleep, she’s usually at the gym, eating extremely spicy food, or wishing she were snowboarding in her native Colorado. Active though she is, she considers staying in bed until noon on Sundays to be important research.