What is sleep apnea?

Sleep apnea is a serious, potentially life-threatening condition that is far more common than generally understood. Sleep apnea occurs in all age groups and both genders. It is more common in men, although it may be under-diagnosed in women and young African-Americans. It is estimated that as many as 18 million Americans have sleep apnea.

Early recognition and treatment of sleep apnea is important, as it may be associated with:

  • Irregular heartbeat

  • High blood pressure

  • Heart attack

  • Stroke

  • Daytime sleepiness

  • Increased risk of motor vehicle accidents

What are the different types of sleep apnea?

Sleep apnea is a breathing disorder characterized by brief interruptions of breathing during sleep. There are two types of sleep apnea:

  • Central sleep apnea occurs when the brain fails to send the appropriate signals to the muscles to initiate breathing. Central sleep apnea is less common than obstructive sleep apnea.

  • Obstructive sleep apnea occurs when air cannot flow into or out of the person's nose or mouth although efforts to breathe continue.

Who is affected by sleep apnea?

Sleep apnea seems to run in some families, suggesting a possible genetic basis. People most likely to have or develop sleep apnea include those who:

  • Snore loudly

  • Are overweight

  • Have high blood pressure

  • Have some physical abnormality in the nose, throat, or other parts of the upper airway

Use of alcohol and sleeping pills increases the frequency and duration of breathing pauses in people with sleep apnea.

What are the characteristics of sleep apnea?

Sleep apnea is characterized by a number of involuntary breathing pauses or "apneic events" during a single night's sleep. There may be as many as 20 to 30 or more events per hour. These events are almost always accompanied by snoring between apnea episodes (although not everyone who snores has sleep apnea). Sleep apnea may also be characterized by choking sensations. The frequent interruptions of deep, restorative sleep often lead to early morning headaches and excessive daytime sleepiness.

During the apneic event, the person is unable to breathe in oxygen and to exhale carbon dioxide, resulting in low levels of oxygen and increased levels of carbon dioxide in the blood. The reduction in oxygen and increase in carbon dioxide alert the brain to resume breathing and cause an arousal. With each arousal, a signal is sent from the brain to the upper airway muscles to open the airway; breathing is resumed, often with a loud snort or gasp. Frequent arousals, although necessary for breathing to restart, prevent a person from getting enough restorative, deep sleep.

What are the causes of sleep apnea?

Certain mechanical and structural problems in the airway cause the interruptions in breathing during sleep. Apnea occurs:

  • When the throat muscles and tongue relax during sleep and partially block the opening of the airway.

  • When the muscles of the soft palate at the base of the tongue and the uvula relax and sag, the airway becomes blocked, making breathing labored and noisy and even stopping it altogether.

  • In obese people when an excess amount of tissue in the airway causes it to be narrowed.

  • With a narrowed airway, the person continues his or her efforts to breathe, but air cannot easily flow into or out of the nose or mouth.

How is sleep apnea diagnosed?

Diagnosis of sleep apnea is not simple because there can be many different causes. Primary care physicians, pulmonologists, neurologists, or other physicians with specialty training in sleep disorders may be involved in making a definitive diagnosis and initiating treatment. Several tests are available for evaluating a person for sleep apnea, including:

  • Polysomnography is a test that records a variety of body functions during sleep, such as the electrical activity of the brain, eye movement, muscle activity, heart rate, respiratory effort, air flow, and blood oxygen levels.

  • Multiple Sleep Latency Test (MSLT) is a test that measures the speed of falling asleep. People without sleep problems usually take an average of 10 to 20 minutes to fall asleep. Individuals who fall asleep in less than five minutes are likely to require some type of treatment for sleep disorders.