For five years, Gary Wessel struggled every day just to stay alert. Each morning, he woke up exhausted. His wife told him he snored. “I felt like I didn’t sleep at all,” said the 45-year-old New York City electrician. All he wanted was a good night’s sleep.

Finally, Dr. Michael Iannuzzi, chairman of pulmonary and critical care medicine at Mount Sinai Medical Center, who was treating Mr. Wessel for an autoimmune disorder called sarcoidosis, suggested he undergo a sleep study to find out if there was an underlying reason for his constant fatigue.

So one night last month, Mr. Wessel checked into Mount Sinai’s Center for Sleep Medicine at 1176 Fifth Avenue. There, he was hooked up to a series of electrodes from head to toe that measured what was happening in his body and brain during the night. The study showed that he had second-level sleep apnea, a problem that closes off his airway and awakens him 20 times each hour during both slow-wave sleep and rapid eye movement, known as REM sleep.

Slow-wave sleep helps restore our ability to remember, concentrate, and learn. REM sleep is the period in which people have vivid dreams, and sleep experts believe it allows them to awaken feeling refreshed and ready to take on the tasks of their day. Mr. Wessel felt neither. “I’d have to fight all day to have energy to get through the day,” he said. “It has been a constant fight to keep going.”

Mr. Wessel was relieved to know what was wrong, but there was more to investigate. Dr. Stasia Wieber, director of the Center for Sleep Medicine and an assistant professor at the Mount Sinai School of Medicine, recommended a Continuous Positive Airway Pressure or CPAP test. The test determined how much air pressure would be required to flow into Mr. Wessel’s airways to keep them open during sleep. Since the study, he has been sleeping with a simple device that allows him to breathe freely throughout the night. He inserts a tube into his mouth and covers his nose and mouth with a small plastic mask that he straps behind his head. He can even carry it with him when traveling to ensure he gets a good night’s sleep. “I definitely feel a lot more alive,” Mr. Wessel reported. “It’s changed my quality of life.”

Mr. Wessel was one of six patients that night to check into the sleep lab for answers about why he couldn’t sleep.

The center expanded from two beds to six in December, to accommodate the city’s increasingly sleepless population. The original two-bed center was booked ahead for months, leaving patients waiting to be treated. The center studied about 725 patients last year and expects to study 1,800 this year. In the sleep lab, sleep apnea is the most common problem treated. Most of the center’s other patients have been referred by their primary care doctors after complaining of insomnia.

The National Sleep Foundation reports that almost seven in 10 Americans experience frequent sleep problems but most go undiagnosed.

Sleepless nights cost Americans more than $100 billion a year in lost productivity, medical expenses, sick leave, and property damage, but the emotional toll is harder to calculate, according to the National Sleep Foundation.

In a 24/7 city like New York, where entertainment and distractions abound, sleep is not a main concern. “Our culture doesn’t make sleeping a priority,” Dr. Wieber said. “It’s our busy lives that become a priority. People say, ‘I’m too busy to sleep. I don’t have time to sleep.’ They work until 10 p.m., then go to the gym or they’re having dinner at 10 p.m.”

She notes that alcohol is a depressant, and 5while it may work as a nightcap, it later disrupts your sleep. The result is the person doesn’t get what she calls “good sleep.” Healthy sleep occurs when we go through the proper stages during four to six cycles per night. The five consecutive stages of sleep, explains Dr. Wieber, are:

1. Light sleep, from which we will awaken if someone walks into the room.

2. Somewhat deeper sleep, from which we will awaken if a drawer slams.

3 & 4. Slow-wave sleep, which is deep and restorative, and from which people are not easily awakened.

5. REM sleep, during which most of our vivid dreaming occurs.

Sleep apnea usually occurs when mechanical or structural problems close off a person’s airway during sleep, causing breathing to stop. Sometimes, apnea occurs when the throat muscles and tongue relax during sleep and partially block the opening of the airway. Sleep apnea can cause death but rarely does, said Dr. Wieber.

Insomnia can be linked to stress, anxiety, or poor sleep habits. Though 75% to 80% of sleep center patients suffer from sleep apnea or insomnia, others have restless leg, periodic limb movement disorder, REM behavior disorder, seizures, nightmares (which can be related to post-traumatic stress), and night terrors.

Typically, when people speak to their primary care doctors about sleep complaints, they ask for some type of sleeping pill. By the time Dr. Wieber sees patients, they are often desperate. “They want a pill yet they want to get off the pill,” she said. “People can develop bad sleep habits, then get anxious about getting to sleep or getting enough sleep. It’s a vicious cycle.”

A sleep study provides sleep specialists with information about the quality and quantity of a person’s sleep: a summary of the individual’s sleep pattern or sleep architecture as the nighttime pattern is known to sleep specialists. “In a sleep lab we do cognitive testing to see how lack of sleep is affecting you,” Dr. Wieber said. “Sleep is under-recognized as an important asset to health.” A sleep study costs $1,500 to $2,000 at Mount Sinai, and is usually covered by insurance.

Not everyone who comes to the center complaining of insomnia undergoes a sleep study. “We don’t do a sleep study unless I detect an underlying problem,” said Dr. Wieber.

When should a person visit a center for sleep medicine? “When they have a sleep problem that lasts more than a week or two. Very often it’s not until they’re desperate that they wind up at the center. If you’re not happy with the quality or quantity of sleep or the way you feel when you wake up, you’re a candidate,” Dr. Wieber said. “I’m striving to make people sleep better so their quality of life improves.”

For more information about Mt. Sinai’s Center for Sleep Medicine, call 212-241-5098 or visit www.mssm.edu.