Sleep onset latency is the time between lying down with the intention to sleep and actually falling asleep. A latency of 15-20 minutes is considered normal. When it consistently exceeds 30 minutes, it is one of the markers of insomnia. Subjective perception of latency tends to be greater than the objective measurement by polysomnography.
Concept origin
The parameter was formalized in polysomnography studies in the 1960s-70s. Carskadon and Dement (1994) documented differences between objective and subjective latency, a key finding: people with insomnia frequently overestimate how long it takes them to fall asleep.
Therapeutic approach
The sleep diary is the standard tool for monitoring subjective latency. Sleep restriction reduces latency by increasing homeostatic pressure. Cognitive restructuring addresses catastrophizing when latency is prolonged.
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