Students who experience excessive daytime fatigue despite getting an adequate amount of sleep at night might unknowingly be suffering from sleep apnea, experts say.

Sleep apnea is a disorder in which a person repeatedly stops breathing while sleeping due to an obstruction in the airway, said Alexandros Vgontzas, a physician and researcher in the department of psychiatry at the Hershey Medical Center.

But he said many people who suffer from sleep apnea do not even realize it.

"When you stop breathing, you awaken for two or three seconds but you don't remember it," Vgontzas said.

He said one symptom of sleep apnea is loud, constant snoring, which can indicate a partial obstruction of the airway.

But people are often unaware that they snore unless someone else is in the room to hear it and let them in on the information.

"A large percentage of sleep apnea cases are undiagnosed," he said.

He said studies at the medical center have revealed that 4 percent of men and 2 percent of women suffer from sleep apnea, but this data is not conclusive because there is no universal criteria to define the disorder.

For example, one study showed that 17 to 19 percent of men and 5 to 6 percent of women stopped breathing more than five times during one hour of sleep, which could be considered mild sleep apnea, he said.

"Sleep apnea is a very, very prevalent problem, but there is not enough public awareness [about it]," he said.

University physician Edward Rosick said sleep apnea becomes more common with age and therefore it is less common among the majority of college students.

"It's not particularly a problem at Penn State," he said.

"We don't really see it a lot."

However he said people who have nasal problems or who are obese are more likely to experience sleep apnea at a younger age.

"If we [at University Health Services] think someone has sleep apnea, we send them to the Sleep Laboratory at Centre Community Hospital," he explained.

The hospital's Sleep Lab uses more advanced equipment, such as electroencephalograms (EEGs), electromyograms (EMGs) and pulse oximeters, to diagnose sleeping disorders, said Gary Barton, a neurotechnician at the Sleep Lab.

"We conduct sleep studies, especially for sleep apnea," he said.

"We wire the patient from head to toe."

He said EEGs monitor the stages of sleep and any abnormal activity in the brain, while EMGs observe the nerve conduction as well as muscle movements.

Pulse oximeters measure the oxygen level in the patient's bloodstream through the use of a laser pointed into the finger.

In addition, chest belts allow the researchers to monitor the patient's breathing, and leg straps, which have motion sensors, show kicking movements that indicate when the patient stops breathing.

The data collected from all of this equipment is analyzed by a computer that runs all night while the patient sleeps, he said.

"The computer looks for sections where the person stops breathing, and then it scores the person according to the number of times they stop breathing," he said.

"There is a certain percentage that [determines the patient] positive for sleep apnea."

He said the information is also scored manually in case the computer makes any mistakes, and then the doctors do further calculations to help determine the severity of the patient's sleeping disorder.

Severe sleep apnea, if untreated, can cause long-term health complications, Rosick said.

"Over decades it can lead to other problems such as heart disease, brain damage, and memory problems," he said.

Sleep apnea has been linked to cardiovascular problems, diabetes, bedwetting and other problems like anxiety, Vgontzas said.

Furthermore, a Reuters Health article reported last month that researchers may have found a link between sleep apnea and the verbal problem of stuttering.

In addition, even mild sleep apnea can cause excessive fatigue during the daytime hours.

"Sleepiness is a problem because it causes accidents," Vgontzas said.

Mild sleep apnea can be treated simply by altering one's daily lifestyle, he said.

"A healthy lifestyle can help sleep apnea," Vgontzas said.

"Weight loss and regular exercise sometimes help."

Severe sleep apnea, on the other hand, requires more drastic treatment.

"One type of treatment is reconstructive surgery on the nasal passages to eliminate the obstruction," Barton said.

"Another treatment is an external respirator like CPAP or BiPAP."

An external respirator, also called a positive air pressure (PAP) mask, is worn overnight.

It blows air in through the patient's nose, forcing the airway to stay open, he said.

Vgontzas said this method is frequently unsuccessful because there is very low compliance among their patients.

"It's uncomfortable, and people get tired of using it," he said.

Rosick said that while PAP masks help patients sleep better, they only cure the symptoms of sleep apnea and don't work at helping cure the disorder itself.

"If they stop using [the mask], they will continue to experience sleep apnea," he said.