In one study, Stanford University researchers looked at 159 truck drivers. They found that 79 percent had sleep apnea, and many were unable to control when they fell asleep driving. In another study looking at accidents in which drivers fell asleep at the wheel, 87 percent of the drivers died, taking with them one or two other people.

Men suffer from the condition almost three times more often than women, , in part because of anatomical differences in the upper airways. But because many women who suffer from it are post-menopausal, there is some speculation it also may be hormone-related, he said.

The most common and severe form of sleep apnea is obstructive sleep apnea. In many cases, it's caused by sagging muscles at the base of the throat, enlarged tonsils, a small airway opening or a large tongue, according to the American Medical Association Encyclopedia of Medicine. In about 20 percent of cases, being overweight is a major cause of the problem.

Obstructing the airway makes breathing labored and causes loud snoring. If there is complete blockage, the breathing stops altogether and the sleeper is briefly silent. This makes the diaphragm and chest muscles work harder; the sleeper gasps and briefly awakes as breathing is started again.

In central sleep apnea, the airway is opened but the diaphragm and chest muscles don't work, perhaps because of a disturbance in the brain's regulation of breathing during sleep, according to the AMA encyclopedia.

If you suspect you're suffering from sleep apnea, talk to your doctor, who may refer you to a lab where your sleep can be monitored. Losing weight and avoiding alcohol before bedtime may help. Wearing a mask attached to an air compressor that forces oxygen into the airway is an effective treatment for severe cases. And surgery that removes excess tissue from the throat is another possibility.

First think through what you want from the doctor and make it clear to him or her. For instance, if you go to the doctor with lower back pain and your blood pressure is high, your doctor may concentrate on treating the blood pressure because it's potentially life-threatening. However you should make it clear the back pain is still something you want treated.

Second, ask questions. Studies show patients who ask questions do better, he said.

Third, be honest about what you can and can't do. If you can't take your medicine four times a day, tell the doctor. Maybe he can give it to you in another form. If you can't diet or exercise, it's important the doctor knows this, too.