ABFM Sleep Medicine key terms

The average number of complete breathing pauses (apneas) plus partial reductions in airflow (hypopneas) per hour of sleep, used to grade obstructive sleep apnea severity.

A partial reduction in airflow during sleep lasting at least ten seconds, scored when it meets a defined drop in airflow and is accompanied by desaturation or an arousal.

The number of times per hour of sleep that blood oxygen falls by a set percentage below baseline, reflecting the frequency of respiratory events with desaturation.

An attended overnight laboratory study recording brain waves, eye movements, muscle tone, airflow, respiratory effort, oxygen saturation, and heart rhythm to stage sleep and diagnose sleep disorders.

An unattended, limited-channel recording performed outside the laboratory that measures breathing and oxygenation to diagnose obstructive sleep apnea in appropriately selected adults with high pretest probability.

A daytime series of nap opportunities measuring how quickly a person falls asleep and whether REM sleep appears, used mainly to evaluate narcolepsy and idiopathic hypersomnia.

A daytime test in which the patient is asked to stay awake in a quiet, dimly lit room across several trials, quantifying ability to remain awake rather than tendency to fall asleep.

The average time from lights out to sleep onset across nap opportunities on a daytime test; very short values indicate pathologic sleepiness.

The appearance of REM sleep within about fifteen minutes of sleep onset, an abnormal finding that supports a diagnosis of narcolepsy when repeated on testing.

The percentage of time spent in bed that is actually spent asleep, calculated by dividing total sleep time by time in bed and multiplying by one hundred.

An abrupt shift in brain wave frequency lasting at least three seconds during sleep, often triggered by breathing events or limb movements and capable of fragmenting sleep.

Repeated brief awakenings or arousals that break up sleep continuity, reducing restorative sleep and causing daytime fatigue even when total sleep time seems adequate.

A disorder in which the upper airway repeatedly collapses during sleep, causing apneas or hypopneas with oxygen drops and arousals, typically with snoring and daytime sleepiness.

Cessation of breathing during sleep caused by absent respiratory effort from reduced brainstem drive, as seen in heart failure or with opioids, rather than by airway blockage.

A cyclic pattern of gradually increasing then decreasing breathing effort followed by a central apnea, commonly seen in heart failure and associated with poor cardiac prognosis.

Treatment that delivers pressurized air through a mask to splint the upper airway open during sleep, the most effective therapy for obstructive sleep apnea.

The degree to which a patient uses positive airway pressure as prescribed, commonly judged by average nightly hours of use and percentage of nights used.

The apnea-hypopnea index remaining during treatment, used to judge whether positive airway pressure settings or another therapy are adequately controlling obstructive sleep apnea.

An oral appliance that holds the lower jaw forward to enlarge the upper airway, an alternative for mild to moderate obstructive sleep apnea or for patients who cannot tolerate positive airway pressure.

A bilevel pressure device that adjusts support breath by breath to stabilize ventilation, used for central sleep apnea such as Cheyne-Stokes respiration in selected patients.

Persistent difficulty falling asleep, staying asleep, or waking too early despite adequate opportunity to sleep, with daytime consequences, occurring at least three nights weekly for months.

A structured, first-line treatment combining sleep education, stimulus control, sleep restriction, cognitive restructuring, and relaxation to change thoughts and habits that maintain insomnia.

A behavioral technique that limits time in bed to roughly the actual sleep duration, then extends it gradually as sleep efficiency improves, building sleep drive.

A behavioral instruction set that reserves the bed for sleep and intimacy, requires leaving bed when awake and uncomfortable, and sets a fixed wake time to strengthen the bed-sleep link.

A sensorimotor disorder with an urge to move the legs, usually with uncomfortable sensations, that begins or worsens at rest and in the evening and improves with movement.

Repetitive, stereotyped leg jerks occurring at intervals of roughly twenty to forty seconds during sleep, often incidental but sometimes causing arousals and nonrestorative sleep.

Worsening of restless legs symptoms, with earlier onset, greater intensity, or spread to the arms, paradoxically triggered by dopaminergic therapy and managed by changing medication.

A drug such as pramipexole or ropinirole that stimulates dopamine receptors and relieves restless legs symptoms, though it risks augmentation with long-term use.

A neurologic disorder of sleep-wake regulation causing excessive sleepiness with cataplexy and low hypocretin, often with sleep paralysis, hypnagogic hallucinations, and sleep-onset REM periods.

Sudden, brief loss of muscle tone triggered by strong emotion such as laughter, with preserved consciousness, the hallmark of narcolepsy type 1.

A hypothalamic neuropeptide (orexin) that stabilizes wakefulness; its deficiency in the cerebrospinal fluid underlies narcolepsy type 1.

An inability to stay awake and alert during the day that interferes with daily function, a symptom shared by sleep deprivation, sleep apnea, narcolepsy, and many medical conditions.

An eight-item questionnaire in which patients rate how likely they are to doze in common situations, giving a quick self-reported measure of daytime sleepiness.

A parasomnia in which normal muscle paralysis during REM sleep is lost, so patients act out dreams with talking, thrashing, or injury; often a precursor of synucleinopathies.

The polysomnographic finding of persistent muscle activity during REM sleep, the objective substrate of REM sleep behavior disorder.

An undesirable physical or experiential event occurring at sleep onset, during sleep, or on awakening, such as sleepwalking, night terrors, or dream-enactment behaviors.

A disorder such as sleepwalking or sleep terrors arising from partial awakening out of deep non-REM sleep, typically with amnesia for the event and often familial in children.

An episode of disoriented, slow, inappropriate behavior or speech after awakening from deep sleep, with the patient difficult to arouse and later amnestic for the event.

A mismatch between the internal body clock and the required sleep-wake schedule or environment, causing insomnia or excessive sleepiness, as in shift work or delayed sleep phase.

A circadian disorder in which sleep onset and wake times are habitually very late relative to social demands, resistant to earlier bedtimes, and improved with timed light and melatonin.

Timed exposure to bright light, usually in the morning, used to shift the body clock earlier in delayed sleep phase and to treat seasonal mood symptoms.

A hormone released by the pineal gland at night that signals darkness and helps time circadian rhythms; taken as a supplement it can advance sleep timing.

Insomnia or excessive sleepiness arising because work hours conflict with the natural circadian rhythm, often with impaired performance and metabolic consequences.

A temporary circadian misalignment after rapid travel across time zones, causing insomnia at night, daytime fatigue, and gastrointestinal upset until the body clock adjusts.

The association between untreated obstructive sleep apnea and hypertension, atrial fibrillation, stroke, and heart failure, mediated by intermittent hypoxemia, sympathetic surges, and intrathoracic pressure swings.

Abnormally low blood oxygen during sleep, seen in sleep apnea and in lung or neuromuscular disease, which can strain the heart and worsen underlying cardiopulmonary illness.

Daytime hypercapnia with elevated carbon dioxide during sleep in a person with obesity, occurring without another cause of hypoventilation and often accompanied by sleep apnea.

Breathing support delivered through a mask without an artificial airway, used for hypoventilation syndromes and chronic respiratory failure to rest breathing muscles and improve gas exchange.

Worsening of asthma control at night from circadian changes in airway tone, inflammation, and reflux, causing cough, wheeze, and awakenings that signal inadequate control.

Backflow of stomach contents that increases when lying flat and during arousals, causing heartburn, cough, and sleep disruption, and sometimes mimicking or worsening sleep apnea.

The bidirectional relationship in which sleep deprivation and sleep itself influence seizure timing, while nocturnal seizures and antiseizure drugs disrupt sleep architecture.

The reciprocal link in which pain fragments sleep and poor sleep lowers pain thresholds and worsens pain perception, making sleep treatment part of pain management.

The close association in which depression commonly causes insomnia or early-morning awakening and reduced REM latency, while insomnia raises the risk of developing depression.

Insufficient sleep relative to need, whether acute or chronic, producing sleepiness, impaired attention and mood, and metabolic and immune effects that resolve with adequate sleep.

The cumulative shortfall between sleep obtained and sleep needed, which impairs performance and mood and can only be repaid by additional sleep.

Operating a vehicle while impaired by sleepiness, a major cause of crashes marked by inattention, microsleeps, and failure to brake, worsened by untreated sleep apnea and shift work.

A set of general habits and environmental practices, such as regular schedules, limiting caffeine and alcohol, and a dark quiet bedroom, that support good sleep but rarely cure insomnia alone.

Changes in sleep across gestation including insomnia, restless legs, and snoring, with new or worsening obstructive sleep apnea linked to gestational hypertension and other maternal risks.

Age-related changes including lighter and more fragmented sleep, more awakenings, earlier sleep timing, and reduced slow-wave sleep, which must be distinguished from a sleep disorder.