ABP Sleep Medicine key terms

The amount of time between lights out and the first appearance of sleep, usually measured in minutes on polysomnography or actigraphy. It is a core metric for insomnia and circadian phase assessment.

The percentage of time spent asleep relative to total time in bed. Values below roughly 85 percent in adults suggest fragmented or insufficient sleep and are commonly reported in insomnia and sleep apnea.

The total minutes spent awake after sleep has begun and before final awakening. It quantifies sleep maintenance difficulty and is elevated in insomnia, apnea, and movement disorders.

The accumulating pressure for sleep that builds with time awake and dissipates during sleep, often modeled as process S. It interacts with circadian timing to determine sleep propensity and alertness.

The endogenous near-24-hour rhythm, driven by the suprachiasmatic nucleus, that modulates sleep-wake tendency, body temperature, and hormone release. It is often modeled as process C opposing homeostatic pressure.

The time in the evening when melatonin rises above a low threshold under dim light. It is a standard marker of circadian phase used to diagnose delayed and advanced circadian rhythm disorders.

The average number of apneas plus hypopneas per hour of sleep. It grades obstructive sleep apnea severity and is the primary polysomnographic summary measure for the disorder.

A partial reduction in airflow during sleep lasting at least ten seconds, scored when it meets amplitude and either desaturation or arousal criteria. Scoring rules differ between adult and pediatric criteria.

The number of oxygen desaturations of a defined depth per hour of sleep, typically three or four percent drops. It reflects intermittent hypoxemia burden in sleep-disordered breathing.

A measure of how strongly a ventilatory control system amplifies a disturbance. High loop gain promotes periodic breathing and central apnea, especially at altitude or in heart failure.

A cyclic pattern of crescendo-decrescendo breathing separated by central apneas or hypopneas, often seen in heart failure. It reflects prolonged circulation time and unstable ventilatory control.

Cessation of airflow during sleep without ongoing respiratory effort, reflecting reduced or absent ventilatory drive. Causes include heart failure, opioids, altitude, and brainstem lesions.

The degree to which a patient uses PAP therapy as prescribed, commonly defined as at least four hours per night on most nights. Adequate adherence is required for Medicare-style coverage and clinical benefit.

The apnea-hypopnea index remaining during positive airway pressure titration or treatment. A persistently elevated value suggests inadequate pressure, mask leak, or a non-obstructive component.

A structured, evidence-based treatment combining sleep restriction, stimulus control, cognitive restructuring, and education. It is first-line therapy for chronic insomnia and outperforms hypnotics over the long term.

A behavioral insomnia treatment that reassociates the bed with sleep by restricting it to sleep and intimacy and by leaving the bed when awake. It targets conditioned arousal at bedtime.

A behavioral treatment that limits time in bed to approximate actual sleep time, then gradually extends it as sleep efficiency improves. It builds homeostatic pressure and consolidates sleep.

A complaint of severely disturbed sleep that is not matched by objective findings on polysomnography or actigraphy. It reflects misperception of sleep state rather than true sleep loss.

The tendency to underestimate time asleep and overestimate sleep latency relative to objective measures. It is common in insomnia and can complicate interpretation of sleep diaries.

A central disorder of hypersomnolence defined by excessive daytime sleepiness plus cataplexy or a low cerebrospinal fluid hypocretin level. It reflects loss of hypocretin-producing neurons.

A sudden, brief loss of muscle tone triggered by emotion, such as laughter, while consciousness is preserved. It is a hallmark of narcolepsy type 1 and reflects REM-related atonia intrusion.

A daytime study of four or five scheduled naps measuring sleep latency and REM onset. Short mean latency with two or more REM-onset naps supports a diagnosis of narcolepsy.

The appearance of REM sleep within about fifteen minutes of sleep onset. It is characteristic of narcolepsy and can also occur in severe sleep deprivation or circadian misalignment.

A central disorder of hypersomnolence with excessive daytime sleepiness and long unrefreshing naps, without cataplexy or hypocretin deficiency. Diagnosis requires excluding other causes of sleepiness.

A circadian rhythm disorder in which sleep onset and wake times are persistently later than desired, causing insomnia and daytime impairment. It is common in adolescents and responds to timed light and melatonin.

Timed exposure to intense light used to shift circadian phase. Morning light advances the rhythm and evening light delays it, making timing critical for circadian sleep-wake disorders.

A circadian rhythm sleep-wake disorder caused by work schedules that conflict with the endogenous clock, producing insomnia or excessive sleepiness. Treatment includes strategic napping, light, and scheduled melatonin.

A parasomnia arising from deep non-REM sleep, including confusional arousals, sleepwalking, and sleep terrors. Episodes typically occur in the first third of the night with impaired awareness.

A partial awakening from slow-wave sleep with disorientation, slow speech, and blunted responsiveness. The episode is usually brief and the patient has little or no recall.

An abrupt arousal from slow-wave sleep with intense fear, screaming, and autonomic activation. The patient is difficult to console and typically does not recall the event.

A parasomnia in which normal REM atonia is lost, so dreams are acted out with movements or vocalizations. It is strongly associated with synucleinopathies such as Parkinson disease.

The polysomnographic finding of persistent muscle tone during REM sleep, scored from chin electromyography. It is the objective substrate of REM sleep behavior disorder.

Repetitive, stereotypic leg movements during sleep, typically lasting under ten seconds and recurring every twenty to forty seconds. They are scored by electromyography and are common in restless legs syndrome.

A sensorimotor disorder with an urge to move the legs, worse at rest and in the evening, relieved by movement. It is a clinical diagnosis often accompanied by periodic limb movements.

An abrupt shift in electroencephalographic frequency lasting at least three seconds, with concurrent autonomic activation. Arousals fragment sleep and are scored to compute arousal indices.

An attended overnight recording of brain waves, eye movements, muscle tone, respiration, oxygen saturation, and cardiac rhythm. It is the reference standard for staging sleep and diagnosing sleep-disordered breathing.

A wrist-worn device that estimates sleep-wake patterns from movement over days to weeks. It is useful for circadian assessment and insomnia monitoring but is not a substitute for polysomnography.

A daytime test measuring the ability to stay awake in a quiet, sedentary setting across several trials. It is used to assess treatment response in excessive sleepiness and fitness for safety-sensitive duties.

Sleep-disordered breathing in children, commonly from adenotonsillar hypertrophy, with different scoring criteria than adults. Symptoms include snoring, labored breathing, and behavioral or learning problems.

Surgical removal of adenoids and tonsils, the first-line treatment for most children with obstructive sleep apnea. Residual disease is common in obesity and requires postoperative reassessment.