ABPN Sleep Medicine key terms

The interval from lights-out to the first epoch scored as sleep on polysomnography or actigraphy. Prolonged latency suggests insomnia or circadian delay, while very short latency may indicate sleep deprivation or a hypersomnia.

Total sleep time divided by time in bed, expressed as a percentage. Values below roughly 85 percent in adults suggest insomnia or poor sleep hygiene, though age-related norms decline in older adults.

The number of apneas plus hypopneas per hour of sleep. Severity bands are commonly 5 to under 15 mild, 15 to 30 moderate, and over 30 severe obstructive sleep apnea.

A partial reduction in airflow during sleep lasting at least 10 seconds. Scoring requires a specified amplitude drop plus either an arousal or a desaturation, depending on the rule set used.

The count of oxygen desaturations of a defined depth (commonly 3 or 4 percent) per hour of sleep. It complements the AHI and reflects the degree of intermittent hypoxemia.

Cessation of airflow for at least 10 seconds without respiratory effort, reflecting absent central drive. Causes include Cheyne-Stokes respiration in heart failure, opioid use, and high-altitude exposure.

A cyclic pattern of crescendo-decrescendo breathing with central apneas, driven by delayed chemoreflex feedback and often seen in heart failure or neurologic disease.

Awake hypercapnia (arterial carbon dioxide above 45 mmHg) in a patient with obesity and no other cause, typically with sleep-disordered breathing. It raises risk of pulmonary hypertension and right heart failure.

Objective use of a PAP device, usually measured as hours per night and proportion of nights meeting a threshold such as 4 hours. Insurance and outcome benchmarks commonly require at least 4 hours on 70 percent of nights.

Delivery of bilevel or volume-targeted ventilatory support through a mask to treat hypoventilation, as in obesity hypoventilation syndrome or neuromuscular weakness, rather than simple obstructive apnea.

An arousal preceded by increasing respiratory effort or flattening of the inspiratory pressure waveform, indicating upper airway resistance without meeting apnea or hypopnea criteria.

Sleepiness and frequent arousals from increased breathing effort with a normal AHI, reflecting flow limitation. It is diagnosed by esophageal pressure or waveform evidence rather than by apnea counts alone.

A daytime nap study with four or five scheduled naps after overnight polysomnography. Mean sleep latency of 8 minutes or less plus two or more sleep-onset REM periods supports narcolepsy.

A daytime protocol measuring ability to stay awake in a quiet, seated situation across several trials. It assesses treatment response and safety rather than diagnosing narcolepsy.

A REM sleep epoch occurring within about 15 minutes of sleep onset in a nap or overnight recording. It is a hallmark of narcolepsy but can occur with severe sleep deprivation or circadian misalignment.

A hypothalamic neuropeptide that stabilizes wakefulness and REM sleep gating. Deficiency, usually from autoimmune loss of producing neurons, causes narcolepsy type 1 with cataplexy and low cerebrospinal fluid levels.

Sudden, brief loss of muscle tone triggered by emotion such as laughter, with preserved consciousness. It is the defining feature of narcolepsy type 1 and reflects REM-related atonia intruding into wakefulness.

Transient inability to move or speak at sleep onset or on awakening while consciousness is retained. It occurs in narcolepsy and, less often, as an isolated benign phenomenon.

Vivid sensory imagery, often visual or auditory, occurring at the transition into sleep. It is a dissociated REM feature and is common in narcolepsy and in healthy people with sleep deprivation.

Vivid sensory experience occurring on awakening from sleep, typically REM sleep. Like hypnagogic imagery, it reflects incomplete dissociation of dreaming from wakefulness.

Excessive daytime sleepiness with long sleep times, unrefreshing naps, and no cataplexy, with normal or prolonged MSLT latency and fewer than two sleep-onset REM periods. Diagnosis is one of exclusion.

Narcolepsy without cataplexy, with MSLT findings of short latency and two or more sleep-onset REM periods but normal hypocretin levels. Cataplexy must be absent and other causes excluded.

Recurrent episodes of severe hypersomnia lasting days to weeks, often with hyperphagia, cognitive change, or disinhibited behavior, separated by normal periods. It mainly affects adolescent males.

A habitual sleep-wake schedule shifted later than desired relative to the internal clock, producing difficulty falling asleep and late awakening. It is common in adolescents and treated with morning light and timed melatonin.

The time in the evening when melatonin rises under dim light, used as a marker of circadian phase. It helps quantify phase delay or advance and guide timing of light and melatonin therapy.

A hormone secreted by the pineal gland at night under circadian control. Exogenous dosing can shift phase when timed correctly and is used for jet lag and circadian rhythm disorders.

Insomnia or excessive sleepiness temporally linked to a work schedule overlapping usual sleep time, causing clinically significant distress or impairment. Treatment includes scheduled sleep, light exposure, and strategic napping.

An NREM parasomnia of partial awakening with disorientation, slow speech, and blunted responsiveness, usually arising from deep sleep early in the night. It is common in children and typically benign.

An abrupt NREM arousal with screaming, autonomic surge, and inconsolability, with little recall afterward. It arises from slow-wave sleep and is distinct from nightmares, which occur in REM.

Complex motor behavior during partial arousal from NREM sleep, ranging from sitting up to walking, with amnesia for the event. It clusters in families and is provoked by sleep deprivation and arousing stimuli.

Acting out dreams with vocalization or limb movement during REM sleep due to loss of normal atonia, confirmed by polysomnography. It often precedes synucleinopathy such as Parkinson disease.

Polysomnographic finding of sustained or excessive muscle tone during REM sleep, the physiologic substrate of dream enactment. It is required for a diagnosis of REM sleep behavior disorder.

Repeated frightening dreams awakening the sleeper from REM sleep with prompt orientation and recall, causing distress or impairment. It differs from sleep terrors by timing, recall, and autonomic intensity.

An urge to move the legs, worse at rest and in the evening, relieved by movement. Diagnosis is clinical; iron deficiency and pregnancy are common contributors, and dopaminergic drugs are used cautiously.

Stereotyped leg movements lasting about 0.5 to 10 seconds, recurring every 20 to 40 seconds, scored on polysomnography. They are common in RLS but can occur without it and are not diagnostic alone.

Worsening of restless legs symptoms with dopaminergic therapy, with earlier onset, greater intensity, or spread to other body parts. Prevention favors avoiding or limiting dopamine agonists.

Wrist-worn monitoring of movement over days to weeks to estimate sleep-wake patterns. It is useful for circadian assessment and insomnia tracking but is less accurate than polysomnography for staging.

A structured, first-line treatment combining sleep restriction, stimulus control, cognitive restructuring, and relaxation. It outperforms hypnotics for durable benefit and is recommended before pharmacotherapy in chronic insomnia.

Behavioral instructions to reserve the bed for sleep and intimacy, leave the bed when awake and frustrated, and return only when sleepy. It strengthens the bed-sleep association in chronic insomnia.

Limiting time in bed to approximate actual sleep time, then gradually extending it as sleep efficiency improves. It builds homeostatic sleep drive and is a core component of CBT-I.

A complaint of little or no sleep despite polysomnographic evidence of near-normal sleep quantity. It reflects misperception of sleep state rather than true sleep loss.

Discrepancy between subjective sleep report and objective measures, with patients underestimating sleep time. It overlaps with paradoxical insomnia and complicates assessment of treatment response.

A graphic display of sleep stages across the night, showing cycles and transitions. It helps visualize sleep architecture, arousals, and REM latency in clinical interpretation.

NREM stage N3, defined by high-amplitude slow activity, predominating in the first third of the night. It is linked to growth hormone release, memory consolidation, and arousal disorders.

A framework in which sleep propensity depends on a homeostatic drive accumulating with wakefulness and a circadian alerting rhythm. The interaction explains timing of sleepiness and vulnerability to shift work.