(from the Greek a (lack of) + pnea (air))
A medical condition in which the tongue, soft palate, and other soft tissues of the mouth and upper throat relax to the point where one's airway is blocked enough to interfere with respiration. It is often characterized by loud snoring, though snoring does not necessarily indicate the condition.
A sleep apnea sufferer will partially awaken in order to resume normal breathing. This can happen dozens or even hundreds of times over the course of a night. The constant partial awakenings, though the patient is not consciously aware of them, make it virtually impossible to reach REM sleep, and thus to get a proper night's sleep.
The patient's bed partner tends to fare little better, for he or she may be awakened by the loud snoring, and frequently must nudge the patient in order to get him or her to start breathing again.
In severe cases, breathing can actually stop completely for several seconds. This can result in a heart attack or stroke. Cass Elliot died due to a heart attack brought on by severe obstructive sleep apnea, and not by choking on a ham sandwich as the myth has it.
Sleep apnea can only be diagnosed properly by spending a night under observation at a sleep clinic. Heart rate, breathing rate, blood oxygen levels, and brain wave patterns (among other things) are monitored as the patient sleeps. This determines how often respiration is interrupted, and whether the apnea is severe enough to interfere with proper sleep. This test is expensive, but it is often covered by insurance.
There are several methods of treatment available. Since the condition is caused by the mass of soft tissue in the mouth and by poor muscle tone in that region, weight loss can make a difference. Surgery is another option, to remove the excess tissue which causes the obstruction, though this is effective only a little more than 50% of the time. The patient can also sleep with a machine known as a CPAP (continuous positive airway pressure), a respirator-like device which supplies pressurized air for the patient to breathe. The high-pressure air forces the patient's airway open. These machines are expensive (US$1500 or more) and count as durable medical equipment, which insurance may not cover completely.
If you suspect that you suffer from sleep apnea, consult your otolaryngologist or ear-nose-throat specialist. He or she can perform some simple tests which will indicate whether a full sleep study is necessary.