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Sleep Apnea

by Kingman P. Strohl, MD

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.

Did You Know...

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

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

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