In a standard sleep study, Sleep Onset Latency measures what?

In a standard sleep study, Sleep Onset Latency measures what?

• A. Time from lights out to the first sleep stage onset
• B. Time from lights out to waking
• C. Time from sleep onset to REM onset
• D. Time in bed

Answer: (A)

Sleep onset latency is the time it takes to fall asleep after lights out—the moment you first enter sleep, usually the first epoch of Stage N1 non-REM sleep. This measures sleep initiation, not how long the night lasts or when REM sleep begins. So if lights go off at 10:00 and you reach the first sleep stage at 10:15, the SOL is 15 minutes.

Sleep onset latency is the time it takes to fall asleep after lights out—the moment you first enter sleep, usually the first epoch of Stage N1 non-REM sleep. This measures sleep initiation, not how long the night lasts or when REM sleep begins. So if lights go off at 10:00 and you reach the first sleep stage at 10:15, the SOL is 15 minutes.