Sleep latency

Sleep latency is the time from lights-out to the first epoch of sleep, typically measured in minutes during polysomnography. A latency of about 10 to 20 minutes is considered healthy; very short latencies (under roughly 5 to 8 minutes) can indicate sleep deprivation or excessive daytime sleepiness, while persistently longer values suggest insomnia or circadian misalignment. It is a core metric in polysomnography and consumer sleep trackers used in longevity contexts.