Sleep apnea syndromes are a group of serious sleep disorders in which breathing repeatedly stops long enough during sleep to decrease the amount of oxygen and increase the amount of carbon dioxide in the blood and brain.

Sleep apnea occurs when breathing is temporarily interrupted during sleep. There are three types.

Obstructive sleep apnea, the most common type, is caused by a blockage in the throat or upper airway. It affects about 4 to 6% of middle-aged men and 1 to 2% of middle-aged women in the United States. Obstructive sleep apnea most commonly occurs in obese people, who tend to sleep on their back. Obesity, perhaps in combination with aging body tissues and other factors, leads to narrowing of the upper airway. Smoking and excessive use of alcohol worsen obstructive sleep apnea. Lung disorders (such as emphysema) contribute to the lack of oxygen. Having a narrow throat and upper airway, which tend to run in families, increases the risk of sleep apnea. In children, enlarged tonsils or adenoids can cause obstructive sleep apnea.

Central sleep apnea, a much rarer type, is caused by dysfunction in the part of the brain that controls breathing (brain stem). Normally, the brain stem is very sensitive to changes in the blood level of carbon dioxide (a by-product of the metabolism of oxygen).

When the level is high, the brain stem signals the respiratory muscles to breathe harder 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. Because the brain stem responds slowly to the buildup of carbon dioxide in the blood, the body’s response is exaggerated, resulting in prolonged hyperventilation.

Similarly, because the brain stem responds slowly to the removal of carbon dioxide from the blood, the body’s response a pause in breathing and is prolonged. Brain stem dysfunction that leads to central sleep apnea may be due to brain tumors. People who have heart failure may have central sleep apnea. In one form of central sleep apnea, called Ondine’s curse, people may breathe inadequately or not at all except when they are fully awake. Central sleep apnea is not associated with obesity.

Mixed sleep apnea, the third type, is a combination of obstructive sleep apnea and central sleep apnea. For example, obstructive sleep apnea sometimes causes central sleep apnea by decreasing oxygen levels and increasing carbon dioxide levels in the blood long enough to cause the brain stem to malfunction. Mixed sleep apnea is rare.

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This entry was posted on Wednesday, May 2nd, 2007 at 3:53 am and is filed under Sleep Apnea. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.