Within the past year, sleep specialists have discovered a new non-surgical treatment for sleep apnea, a disorder in which the individual temporarily stops breathing while he sleeps. That can cause serious cardiovascular and arterial problems and, until now, was treated mostly with surgery.

According to Dr. Wallace Mendelson, chief of sleep studies at the National Institute of Mental Health, the new treatment relies on a device called the "C-PAP," continuous positive air pressure. It is, said Mendelson, "a little machine about the size of a small TV set that just sits on your bed table. A hose goes to a little mask that fits on your nose, and it exerts a tiny bit of air pressure into the upper throat. That is just enough to open up the airway."

As a result, people who previously would have required surgery can be helped to sleep with this device instead.

"It is really a marvelous thing," Mendelson said. "It is non-invasive for one thing. A lot of people who have apnea, including many older people, are not good surgical candidates. Here's a very lovely treatment that will handle many of the patients."

The C-PAP, as it turns out, does more than just keep the throat open, Mendelson said. For example, patients on a steady treatment -- using it, say, four nights a week -- find that they do better the other nights as well. They actually seem to increase the muscle tone."

A change in the technology only in the past year has made the C-PAP -- until now used in hospitals for certain pulmonary patients -- small enough and inexpensive enough to be used by patients at home, Mendelson said.

Sleep apnea affects about 1 million Americans, including children and the elderly. It is especially prevalent among middle-aged, overweight males with short, thick necks. It is often associated with loud snoring.

It is one of the disorders discovered by sleep researchers only in the past decade or so, and although it is potentially fatal, it has been notoriously resistent to treatment.

People with apena stop breathing usually for about 10 to 15 seconds at a time, sometimes hundreds of times during the night. Efforts to resume breathing or the lack of oxygen itself cause the person to wake up each time and start breathing again. These hundreds of mini-wakenings may go unnoticed by the victim, but may have serious side effects and daytime symptoms, primarily daytime sleepiness.

It is often caused when flabby throat muscles and tissue permit the tongue to fall back and block the flow of air, or when the pharyngeal wall tends to collapse during sleep. This phenomenon is known as obstructive apnea, and can be helped by surgery.

Another kind of sleep apnea occurs when the respiratory center in the brain fails to signal a breathing command to the body. Most cases involve a combination of the two types.

The most serious cases may require a tracheostomy, a permanent hole into the windpipe -- life-saving, but requiring changes in life style not always acceptable to the patient.

More recently, specialists have developed a less radical operation known as UvuloPalatoPharyngoPlasty (UPPP), which is said to be up to 95 percent effective in snore control and somewhat less effective for eliminating sleep apnea.

Mendelson and his colleagues at NIMH are currently investigating the relationship between sleep disorders and behavioral as well as physiological problems. For example, he said recently, "when sleep apnea first became well known, people concentrated on the medical consequences of it, which are very real -- hypertension and heart disease, for example, and people concentrated on that.

"Now, however, it is becoming clear that there are some real psychological consequences, and it is my belief that a fair number of people thought to have depression, and who are unsuccessfully treated for depression, actually have sleep apnea. Many of the people with sleep apnea develop trouble with memory, have trouble concentrating, are irritable, moody, have sexual difficulties and some develop unreasonable jealousies.

"And," he said, "the reason I emphasize this is that I've just given you a list of the symptoms of depression. Often the sleep apnea isn't recognized by the physician, because he isn't looking for it. Obviously, I think this is a small minority, but I think it is an overlooked cause of depression."

Researchers are finding similar things among children as well.

"There are many cases of kids who have always been straight arrows and do well in school, and then suddenly over the course of six months, the teacher will be writing notes home to parents that they are being impulsive and aggressive, and all sorts of bad things. Then you study the youngsters and find out they have sleep apnea.

"And in kids," Mendelson continued, "treating it is often just a matter of taking out tonsils and adenoids that were blocking proper breathing at night, and the behavior problems clear up. So you can actually treat behavior surgically."