Table 1
Definitions of sleep terminology.
| | Term | Definition |
| | Sleep disturbance | Sleep pattern divergent of what is considered to be normal as objectively measured, for example, by polysomnography. | | Sleep disorder | Medical disorder involving sleep, resulting in suffering or reduced functioning, including dyssomnias and parasomnias. | | Sleep onset latency | Time interval between time of turning of the lights and onset of sleep. | | Sleep efficiency | Ratio of the time spent asleep to the amount of time spent in bed. | | Chronotype | Individual internal timing type regarding preferred time for mental and physical activity and sleep. | | Homeostatic sleep drive | Drive to sleep that gradually increases with prolonged wakefulness and decreases during sleep. | | Sleep fragmentation | Disrupted sleep cycle due to interruption of a sleep stage, as a result of the appearance of a lighter sleep stage or wakefulness. | | Sleep phase advance | Forward shift of the sleep/wake rhythm, as demonstrated by the time of the nocturnal elevation of plasma melatonin. | | Insomnia | Sleep disorder comprising difficulty initiating and/or maintaining sleep or nonrestorative sleep for at least one month, resulting in significant distress and/or impaired daytime functioning | | REM sleep behavior disorder | Parasomnia characterized by “acting out” of dreams during REM sleep due to absence of normally occurring muscle atonia. | | Excessive daytime sleepiness | Parasomnia characterized by excessive sleepiness during the day, often with hypersomnia and the occurrence of sleep attacks. | | Periodic limb movement disorder | Sleep disorder characterized by involuntary limb movements causing fragmented sleep. | | Restless legs syndrome | Syndrome characterized by unpleasant sensations in one or more limbs, exacerbated by rest and relieved with activity, paired with a strong urge to move the affected limbs, often with paresthesias or dysesthesias. |
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