ABIM Sleep Medicine key terms

The time in minutes from lights-out to the first epoch scored as sleep on polysomnography or actigraphy. It is a core endpoint for insomnia and for the multiple sleep latency test.

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 rather than simply short sleep.

The accumulated drive to sleep that rises with time awake and dissipates during sleep, often indexed by slow-wave activity. It is modeled as process S interacting with the circadian process C.

A framework describing sleep timing as the interaction of a homeostatic sleep drive that builds during wake and a circadian alerting rhythm. Sleep propensity peaks when both processes align.

Non-REM stage N3 sleep, defined by epochs containing at least 20 percent high-amplitude slow waves (0.5 to 2 Hz). It predominates in the first third of the night and reflects homeostatic recovery.

The proportional distribution and cycling of sleep stages across the night, typically about 5 percent N1, 45 to 55 percent N2, 15 to 25 percent N3, and 20 to 25 percent REM in healthy adults.

A sleep stage with mixed-frequency low-amplitude EEG, rapid eye movements, and skeletal muscle atonia, occurring in cycles roughly every 90 minutes and lengthening toward morning. Dream recall is common.

A structured multicomponent treatment combining sleep restriction, stimulus control, cognitive restructuring, and relaxation, delivered in person or digitally. It is first-line therapy for chronic insomnia in adults.

A behavioral technique that limits time in bed to approximately the patient's estimated total sleep time, then extends it gradually as sleep efficiency improves. Daytime sleepiness must be monitored during titration.

Instructions designed to strengthen the bed as a cue for sleep: go to bed only when sleepy, leave the bed if awake and restless, and reserve the bed for sleep and intimacy.

A prospective two-week log of bedtimes, wake times, naps, and subjective sleep quality. It estimates sleep patterns and guides behavioral treatment, and it is a required component of insomnia assessment.

A presentation in which patients report severe insomnia without objective polysomnographic evidence of markedly short sleep or daytime impairment. It is sometimes called sleep state misperception.

The number of apneas plus hypopneas per hour of sleep. It grades obstructive sleep apnea severity as mild (5 to under 15), moderate (15 to under 30), or severe (30 or more).

A reduction in airflow of at least 30 percent lasting at least 10 seconds, accompanied by a 3 percent oxygen desaturation or an arousal, depending on the scoring rule applied.

The number of oxygen desaturations of at least 3 or 4 percent per hour of recording. It is a supportive metric in home sleep apnea testing and in patients with comorbid cardiopulmonary disease.

Cessation of airflow without respiratory effort, often driven by loop gain instability in heart failure or by opioid use. Cheyne-Stokes respiration is a cyclic form seen in systolic heart failure.

Delivery of pressurized air through a nasal or oronasal interface to splint the upper airway open. Modes include fixed CPAP, auto-titrating PAP, and bilevel or adaptive servo-ventilation.

A custom mandibular advancement device that protrudes the lower jaw to enlarge the pharyngeal airway. It suits mild to moderate obstructive sleep apnea and patients intolerant of positive airway pressure.

A daytime study of four or five nap opportunities spaced two hours apart that measures mean sleep-onset latency and the number of sleep-onset REM periods. It supports the diagnosis of narcolepsy and idiopathic hypersomnia.

A daytime protocol in which the patient attempts to remain awake in a quiet, dimly lit room across four trials. It assesses treatment response and fitness for safety-sensitive duties rather than diagnosing hypersomnia.

A central disorder of hypersomnolence with excessive daytime sleepiness and cataplexy, usually caused by hypocretin neuron loss. Cerebrospinal fluid hypocretin-1 is low in most cases.

A sudden, brief loss of skeletal muscle tone triggered by strong emotion, with preserved consciousness. It is the defining feature of narcolepsy type 1 and reflects REM-related atonia intruding into wakefulness.

A central disorder of hypersomnolence with excessive daytime sleepiness, long unrefreshing naps, and prolonged sleep times, without cataplexy and with normal or near-normal hypocretin levels.

The time at which salivary or plasma melatonin begins to rise under dim light, marking circadian phase. It is used to diagnose delayed and advanced circadian phase disorders and to time light or melatonin therapy.

A circadian rhythm disorder in which sleep onset and wake times are persistently later than desired, causing insomnia at bedtime and difficulty waking. Morning light exposure and appropriately timed melatonin are treatments.

Insomnia or excessive sleepiness temporally linked to a work schedule outside conventional daytime hours and associated with clinically significant distress or impairment. Planned light exposure and strategic napping help.

A parasomnia of dream enactment with vocalizations or complex movements during REM sleep, confirmed by polysomnographic REM sleep without atonia. It often heralds synucleinopathy neurodegeneration.

Sustained or excessive chin or limb electromyographic activity during REM sleep on polysomnography. It is the required objective finding for REM sleep behavior disorder and can occur with antidepressants.

A non-REM parasomnia of partial awakening with disorientation, slow speech, and blunted responsiveness, usually arising from slow-wave sleep early in the night. Patients are typically amnestic for the episode.

A non-REM parasomnia with abrupt arousal from slow-wave sleep featuring a scream, intense fear, tachycardia, and inconsolability, with no memory of the event afterward. It is most common in children.

A sensorimotor disorder with an urge to move the legs that is worse at rest and in the evening and is relieved by movement. Iron deficiency and dopaminergic dysfunction are implicated.

Repetitive, stereotyped limb movements lasting 0.5 to 10 seconds, occurring at intervals of 5 to 90 seconds during sleep. The periodic limb movement index is reported on polysomnography.

Worsening of restless legs syndrome during dopaminergic therapy, with earlier onset of symptoms, greater intensity, and spread to other body parts. It is a key reason to avoid dopamine agonists as first-line treatment.

The number of electroencephalographic arousals per hour of sleep, each requiring an abrupt shift in EEG frequency lasting at least 3 seconds. It quantifies sleep fragmentation from apnea, movements, or other causes.

An arousal following a sequence of increasing respiratory effort or flattening of the inspiratory pressure waveform, without meeting hypopnea criteria. It identifies upper airway resistance syndrome.

An unattended recording, typically of airflow, respiratory effort, oximetry, and sometimes position, used to diagnose obstructive sleep apnea in appropriate adults. It underestimates severity and cannot reliably detect central events.

An attended overnight recording of EEG, eye movements, chin and limb electromyography, airflow, respiratory effort, oximetry, ECG, and body position. It is the reference standard for staging sleep and scoring respiratory events.

A wrist-worn device that estimates rest-activity patterns over days to weeks. It supports assessment of circadian rhythm disorders, insomnia, and treatment response, and it complements rather than replaces the sleep diary.

Sleep-disordered breathing that may worsen across gestation because of weight gain, edema, and reduced functional residual capacity. It is associated with hypertensive disorders and should be treated with positive airway pressure.

Insomnia in young children arising from sleep-onset associations or inadequate limit setting, treated with graduated extinction and consistent bedtime routines. Parental education is central to management.