Gary Stewart never had trouble falling asleep, but he seldom felt rested, even after a full night's sleep. Then there was the nightly racket of his snoring.

Stewart sought treatment late last year after adding 45 pounds to his 230-pound frame. The extra weight further constricted his breathing passages and made it even more difficult to get a restful sleep. His worsening condition left him sluggish, sleepy and depressed.

``Trying to watch `Lord of the Rings' without falling asleep was nearly impossible,'' said Stewart, a record company executive in his 40s. ``And those art films, forget it.''

In January, after a physician's recommendation, Stewart underwent a polysomnogram, or sleep study. He was diagnosed with sleep apnea, a condition characterized by brief breathing interruptions during sleep. An estimated 20 million Americans suffer from the condition, whose symptoms range from the merely annoying to the potentially deadly.

The most common signs of the disorder are morning headaches, loud snoring, irritability and difficulty concentrating. Left undiagnosed or untreated, it can cause high blood pressure, sexual dysfunction and depression. People with sleep apnea often have difficulty staying awake at work, or may fall asleep at inappropriate times. They are three times more likely to be involved in an automobile accident.

A sleep study, which costs about $1,500 and is usually covered by health insurance, is often used to diagnose the condition. The study, in which the patient is monitored by medical specialists while sleeping, measures bodily functions such as brain waves, eye movement, heart rate and air flow.

In a patient like Stewart, in which sleep apnea is suspected, doctors are especially watching for halts in breathing. ``Everyone, including myself, has a breathing pause during sleep,'' said Dr. Frisca L. Yan-Go, medical director of the Sleep Disorders Center at Santa Monica-UCLA Medical Center.

She explains that as many as five breathing pauses an hour, lasting a few seconds, are normal. But people with sleep apnea may have as many as 60 stoppages, lasting 10 seconds or more in severe cases.

The interruptions trigger a ``fight or flight'' response in the brain, rousing the person from sleep in order to breathe again. These frequent stoppages can prevent a person from obtaining so-called REM (rapid eye movement) sleep, which is essential for feeling properly rested.

Diagnosing the problem

In most cases, a patient has to spend the night in a sleep clinic to be tested. At the University of California-Los Angeles clinic, patients typically arrive an hour or so before their normal bedtime. The patient then spends the next 30 to 40 minutes being outfitted with electrodes for sleep. The monitoring devices are affixed to the head, chest and legs. (The latter helps measure restlessness during sleep, even though the sleep sessions often are videotaped as well.)

To supplement the medical data, patients are also asked to keep a written daily record that includes their bedtime, how long it took them to fall asleep and total hours slept.

Also, spouses or roommates, who are often the first ones to sound the alarm about the condition, are asked to fill out a questionnaire to track such traits as snoring volume, restlessness and teeth grinding. Their months or years of complaining about wall-rattling snoring will be validated in the sleep study, which provides a printout of snoring volume. Stewart's study showed he had severe sleep apnea. He stopped breathing during sleep as many as 60 times an hour.

The question now was treatment. Like many patients, Stewart opted for continuous positive airway pressure, or CPAP, therapy. The therapy consists of wearing headgear and a mask hooked up to a shoebox-size machine that delivers pressurized air to the sleeper. The constant and continuous forced air helps prevent breathing pauses by keeping the nasal passages open.

In addition to the CPAP, Stewart also considered surgery. There are several procedures to attack the problem, but the most common one calls for the removal of excess tissue at the back of the throat. The surgery can be quite painful and is thought to be effective in only 30 percent to 60 percent of cases.

But sleeping every night with a mask over your face has obvious drawbacks. ``Just picture yourself as the Dennis Hopper character in `Blue Velvet,' '' jokes Stewart, adding, ``Actually, it's not that bad.''

Stewart experienced some common problems with CPAP, still considered one of the most effective treatments for sleep apnea. After more than six months of using the therapy, he is still making minor adjustments with the mask and the intensity of the airflow.

Problems with CPAP are fairly common, and as many as one in four patients at the UCLA clinic eventually quits the therapy in frustration, said Yan-Go. Dropout rates can run much higher at other clinics if patients receive little training on the proper use of the device, she said.

Another treatment

But another sleep apnea sufferer, Joanne Murphy of Rancho Santa Fe, found great relief in one of the several variations of the CPAP device, known as the bi-level positive airway pressure, or BPAP, machine. The bi-level simply supplies more pressurized air breathing in than out, thus reducing the often disconcerting feeling of exhaling into a wind.

``The difference for me was like night and day,'' said Murphy, 50, a former saleswoman and singer. ``You wake up and you don't ache, you feel rested and it's like, `Oh, my God. It's a beautiful morning. Is this how everyone else feels?' ''

Stewart, meantime, says life is ``slightly to noticeably better'' since beginning therapy. He is also pursuing lifestyle changes meant to further mitigate his symptoms. The single man is trying to lose weight and exercise more frequently.

``Women want a man that sleeps well,'' he said. ``Sleep-ism is really an underrated phenomenon.''