All about sleep apnea
MySleepCentral.com
The term apnea means a pause in breathing. Everyone takes small pauses occasionally in breathing; however, it is abnormal to pause your breathing during sleep for 10 seconds or longer. When breathing completely stops for this long, the term apnea is used. When breathing continues, but is decreased to half of what it had been for 10 or more seconds, the term hypopnea is used.
A condition that includes both apnea and hypopnea is commonly known as obstructive sleep apnea. It is being renamed to be more inclusive of other similar problems and will soon be called obstructive sleep apnea hypopnea syndrome (OSAHS). OSAHS is a disease in which the airway, somewhere from the nostrils to the vocal cords, collapses or closes off during sleep. One of the most fascinating features about this syndrome is that it only occurs in sleep.
Who Gets OSAHS?
What causes a collapse in the upper airway, so one cannot take normal breaths during sleep? It looks as if the primary risk factor for OSAHS in adults is being overweight. Doctors are not entirely sure why being overweight cause apneas. They do know, however, that fat can deposit in certain areas of the upper airway and tongue, making the airway smaller. It also seems that the upper airway is shaped differently in overweight people, which may make the airway more collapsible.
Not everyone who gets OSAHS is overweight. In fact, the biggest risk factor for children is large tonsils. Other people (adults and children) are simply born with narrowed nasal passages, small facial bones (cheek bones and/or jaw bones), or extra-soft tissues within the backs of their throats.
OSAHS is a relatively common disease. At least 4 percent of adult males in the United States have OSAHS and 2 percent of adult females have the disease. As people age, they commonly gain more weight, which causes the upper airway tissues to sag and become more collapsible. For these reasons, OSAHS is even more common in older individuals. Although doctors are still uncertain of the exact numbers, this disease is most likely present in at least 1 percent of children.
Understanding Your Body
When people have OSAHS, why do they breathe normally while awake, but not while asleep? Individuals who have OSAHS use the muscles in the nose, throat and neck to keep the airway perfectly open while awake. One of these muscles is located within the tongue. Most of the tongue is a muscle and, while awake, people keep their tongues forward in their mouths in order to keep the airway behind the tongue open.
Other muscles are located within the uvula (the floppy tissue that hangs down in the back of the throat). The uvula has small muscles within it that pull it forward, up, and out of the way for breathing. Other muscles are below the jaw on the front of the neck. These muscles pull the neck tissues forward to keep the rest of the upper airway open.
Everyone has different anatomy. Some people with OSAHS have large tongues and their main problem in sleep is that the tongue moves toward the back of the mouth and closes off the airway. Other people have small facial bones, narrowed nasal passages, a large uvula, large tonsils, or a large neck. All of these people use different combinations of the upper airway muscles described above to keep their airways open. By using some or all of these muscles while they are awake, people do not snore and their breathing is perfectly normal. When someone goes to sleep, it is normal for muscles throughout the body to relax and the airway muscles are no exception. As these muscles relax, the tongue or uvula can fall back in the throat and block the airway; whichever muscles are helping to keep the airway open may relax in sleep and no longer do their job sufficiently. If the airway is completely blocked, a person has an apnea. If it is only partly blocked, the person has a hypopnea.
When people with OSAHS fall asleep and the muscles within the upper airway relax, the amount of air reaching the lungs decreases. This means that the blood oxygen levels will drop and the carbon dioxide levels in the blood will rise.
The degree to which an individual's oxygen level drops depends upon how much that person weighs (heavy people have faster and more significant drops in their oxygen levels), how much breathing stops, and how low the person's oxygen level was before sleep. Low blood oxygen levels from apneas and hypopneas decrease the amount of oxygen that the brain, heart and other organs receive. This puts stress on these organs and may predispose people with OSAHS to strokes and heart attacks.
Low oxygen levels continually wake up patients, so that no matter how many hours they sleep, they still feel groggy. Due to the frequent wake ups, people with untreated OSAHS may never get into a deep or dream sleep. The sleepiness, and maybe the low oxygen levels, can have serious adverse consequences on daily life activities including driving and job performance.
Aside from low oxygen levels and sleepiness, people with OSAHS may wake up frequently feeling as if they are suffocating. This sends a big jolt of adrenaline through the body causing the blood pressure to suddenly increase and the heart to race. Studies are under way, which hopefully will determine how dangerous this is for the heart; intuitively, it does not sound healthy to have boosts in adrenaline all through the night. Not all patients remember these episodes because they quickly fall back to sleep and lose the memory of these events.
There are other problems that OSAHS can cause, including reduced sexual performance with a lower sex drive and/or the inability to achieve an erection for males. OSAHS frequently sends bed-partners to sleep in separate bedrooms because of the noise of the apneas. Finally, a substantial number of people with OSAHS have at least a mild depression. The good news is that most of these symptoms can improve dramatically with adequate treatment.
Date published: June 1998
Date reviewed: August 30, 1999 This content has been reviewed for medical accuracy by
Dartmouth Medical School
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