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Sleep Disorders Center: GLOSSARY

APNEA - A complete collapse of the breathing passageway during sleep. With the airway blocked, no breathing occurs and oxygen levels drop. In order to breathe again you must wake up briefly gasping for air, which leads to non‑restful sleep.

AROUSAL - A shift in a person’s level of sleep with a momentary awakening that usually goes unnoticed. These arousals can follow snores, apneas, hypopneas, and sounds.

AWAKENING - An abrupt or gradual change in a person’s sleep, that results in attaining an alert state of mind.

CIRCADIAN RHYTHM - The biological process of a natural rhythm during a 24 hour period. The circadian rhythm is easily upset by shift work and jet lag.

CATAPLEXY - A symptom of narcolepsy. A sudden, brief loss of muscle control, usually triggered by strong emotion, such as laughter, surprise, or anger.

CPAP - Continuous Positive Airway Pressure. The primary and highly effective method of therapy for treating sleep apnea. CPAP machines work by delivering room air through a mask that is fitted over the nose. This air pressure acts as a splint to keep the airway open, allowing normal breathing patterns to be maintained.

EDS - Excessive Daytime Sleepiness. A constant feeling that an individual can’t remain awake and alert, especially if you’re relaxing. EDS often leads to a pattern of repetitive napping.

HYPOPNEA - A partial collapse of the breathing passageway during sleep. Like apneas, hypopneas have the same symptoms and lead to non-restful sleep.

INSOMNIA - The inability to fall asleep within a reasonable amount of time or the inability to remain asleep, once a person has gone to sleep.

MSLT - Multiple Sleep Latency Test. A scientific validated objective test of excessive sleepiness. A MSLT is commonly used after a polysomnogram in which narcolepsy is suspected.

NARCOLEPSY - Excessive drowsiness with a tendency to sleep at inappropriate times. The episodes of narcolepsy may be brought on by stressful situations and may not be completely relieved with sleep. Some symptoms of narcolepsy include EDS, cataplexy, and sleep paralysis.

PLMD - Periodic Limb Movement Disorder. A disorder in which there is an involuntary movement of the limbs while a person is asleep. This may affect a person’s ability to sleep and to function normally during the day.

POLYSOMNOGRAM - A technical term for a sleep study. A recording that includes measurements to monitor brain waves, breathing, heart rate and rhythm, oxygen levels, and other physiological variables to determine if there are sleep pattern deficiencies.

REM SLEEP - Rapid Eye Movement Sleep. The stage of sleep with heightened brain activity and a reduction of muscle tension in the body. The dream state of sleep. Considered to be needed for mental restoration.

RLS - Restless Leg Syndrome. A "creepy, crawly" sensation that occurs in the legs when a person is sitting or lying still, especially at bedtime. Many people who have RLS also have PLMD.

SLOW WAVE - The stages of sleep characterized by brain waves of slow duration.

SLEEP - Considered to be needed for physical restoration.

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