Obstructive Sleep Apnea

Obstructive sleep apnea, or OSA, arises from what is basically a mechanical problem. During sleep the patient's tongue falls back against his or her soft palate, and the soft palate and uvula fall back against the back of the throat, effectively closing the airway.

Result: when the sleeper expands the chest to inhale, no air enters the lungs.

Why this blockage occurs is some people and not others is not clear. The condition appears to develop more frequently among people who sleep on their back, are middle-aged, are overweight, and are male. The differences are relative, however. OSA is seen in both sexes and in patients of all ages, body types, and favored sleeping positions.

Some researchers believe the mechanical failings that give rise to OSA are neurological in origin, that the flaccidity of the tongue and throat muscles results from improper or inadequate signaling from the brain.

Whatever its cause, OSA left untreated is a serious matter. In many cases it leads to debilitating daytime sleepiness, morning headaches, depression, and a general sense of unwellness. Over time it gives rise to high blood pressure, heart disease, strokes, diabetes, and other life-threatening and life-shortening diseases.

Wikipedia and PubMed Health offer more detailed discussions of OSA.

Habib M'henni/Wikimedia Commons
As this graphic shows, this sleeper's tongue has fallen back against the soft palate, the soft palate has collapsed against the back of the throat, and both the nasal and the oral airways are obstructed, creating an apnea.