ABA Sleep Medicine key terms

The average number of apneas plus hypopneas per hour of sleep, calculated by dividing the total event count by total sleep time. It is the primary metric used to grade obstructive sleep apnea severity.

An abnormal reduction in airflow during sleep lasting at least ten seconds, usually scored when breathing amplitude falls by a defined percentage and is accompanied by desaturation or arousal.

The number of times per hour of sleep that oxygen saturation drops by a specified amount below baseline. It reflects intermittent hypoxemia burden and is often reported alongside the apnea-hypopnea index.

A partial narrowing of the upper airway that flattens the inspiratory flow waveform without meeting criteria for a hypopnea. It signals increased breathing effort and airway resistance.

A condition with excessive daytime sleepiness and repetitive respiratory effort-related arousals from increased airway resistance, occurring without frank apneas or hypopneas and with normal oxygen saturation.

Cessation of airflow during sleep caused by absent or diminished respiratory effort from the brainstem, rather than by upper airway obstruction. It is scored when effort signals are flat.

A cyclic breathing pattern of gradually increasing then decreasing tidal volume separated by central apneas or hypopneas. It is most often seen in heart failure and at high altitude.

A measure of the stability of the respiratory control system, describing how strongly a disturbance in ventilation drives a corrective response. High loop gain promotes periodic breathing and central apneas.

Delivery of pressurized air through a nasal or oronasal interface to splint the upper airway open during sleep. It is the standard treatment for obstructive sleep apnea.

A mode of positive airway pressure that maintains a constant pressure throughout the respiratory cycle to prevent upper airway collapse in obstructive sleep apnea.

The apnea-hypopnea index remaining while a patient is using positive airway pressure or another therapy. It indicates how well the treatment controls breathing events.

A comprehensive overnight recording of sleep that includes brain waves, eye movements, muscle tone, airflow, respiratory effort, oxygen saturation, heart rhythm, and body position. It is the reference standard for diagnosing sleep disorders.

An abrupt shift in brain wave frequency during sleep lasting at least three seconds, often accompanied by increased muscle tone. Arousals fragment sleep and are scored from the EEG.

An arousal that follows a respiratory event such as increased breathing effort or a hypopnea. It is scored when the arousal occurs within a short interval after the event.

The percentage of time in bed actually spent asleep, calculated as total sleep time divided by time in bed. Low values suggest difficulty initiating or maintaining sleep.

The time from lights out to the first epoch of sleep. It is a key measure in insomnia assessment and in the multiple sleep latency test.

A daytime series of nap opportunities after overnight polysomnography that measures how quickly a person falls asleep. It is used mainly to evaluate excessive daytime sleepiness and narcolepsy.

A daytime test measuring how long a person can stay awake under quiet conditions across several trials. It assesses ability to remain alert rather than sleepiness.

The appearance of rapid eye movement sleep within about fifteen minutes of sleep onset. It is a supportive feature of narcolepsy when seen on polysomnography or the multiple sleep latency test.

A neurological disorder of sleep-wake regulation marked by excessive daytime sleepiness and, in many cases, cataplexy, sleep paralysis, hypnagogic hallucinations, and sleep-onset REM periods.

A sudden, brief loss of muscle tone triggered by strong emotion such as laughter, while consciousness is preserved. It is a hallmark of narcolepsy type 1.

A neuropeptide produced in the lateral hypothalamus that stabilizes wakefulness. Deficiency of hypocretin-producing neurons underlies narcolepsy type 1.

A short self-report questionnaire in which a person rates the likelihood of dozing in eight everyday situations. It gives a subjective measure of daytime sleepiness.

Persistent difficulty falling asleep, staying asleep, or waking too early, with daytime consequences, occurring despite adequate opportunity to sleep. It is diagnosed clinically rather than by polysomnography.

A structured, evidence-based psychological treatment for insomnia that combines sleep education, stimulus control, sleep restriction, cognitive restructuring, and relaxation training. It is first-line therapy for chronic insomnia.

A behavioral treatment that limits time in bed to the estimated average sleep duration, then gradually extends it as sleep efficiency improves. It builds homeostatic sleep drive.

A behavioral technique that strengthens the association between the bed and sleep by restricting the bed to sleep and intimacy and by leaving the bed when unable to sleep.

An internally generated cycle of roughly twenty-four hours that governs timing of sleep, hormone release, body temperature, and alertness. It is synchronized to the environment by light.

A hormone secreted by the pineal gland mainly in darkness that signals biological night and helps time sleep. It is used clinically to shift circadian phase.

A shift of the internal circadian clock to a later time, producing later sleep and wake times. It is typical of delayed sleep-wake phase disorder and is treated with timed morning light.

An urge to move the legs, usually with uncomfortable sensations, that begins or worsens at rest and in the evening and is relieved by movement. It follows a circadian pattern.

Repetitive, stereotyped leg movements during sleep, typically lasting a fraction of a second to a few seconds and recurring at intervals of roughly twenty to forty seconds. They may cause arousals.

Insufficient body iron stores, reflected by low ferritin, that can worsen restless legs syndrome. Iron status is routinely assessed and treated in affected patients.

An abnormal behavior or experience arising from deep non-REM sleep, such as sleepwalking or sleep terrors, often with partial awakening and limited recall.

A parasomnia in which normal muscle paralysis during REM sleep is lost, so people act out dreams, sometimes violently. It can precede neurodegenerative disease.

The profound loss of skeletal muscle tone that normally occurs during rapid eye movement sleep. Its failure permits dream enactment behavior.

A non-REM parasomnia in which a person awakens partially, appearing confused and disoriented, often with slow speech and little memory of the event.

The increased chance of airway complications, difficult intubation, and postoperative respiratory depression in patients with obstructive sleep apnea undergoing surgery or sedation. Screening and planning reduce harm.

A short screening tool for obstructive sleep apnea that scores snoring, tiredness, observed apneas, pressure, body mass index, age, neck circumference, and gender to estimate risk.