what is sleep latency

Sleep latency, also known as sleep onset latency (SOL), is the amount of time it takes to fall asleep once you go to bed. It is the length of time that it takes to accomplish the transition from full wakefulness to sleep, normally to the lightest of the non-REM sleep stages. Sleep latency is an important measure because it can reflect a person’s overall sleepiness and provide insight into sleep quality. A normal sleep latency generally hovers between 10 and 20 minutes. However, different people experience different sleep latencies, and an extremely short sleep latency of less than eight minutes indicates increased sleepiness and could be the result of sleep deprivation or poor sleep due to an underlying sleep disorder. Sleep latency can be an indicator of the overall quality of sleep, and quickly falling asleep during the day and rapidly entering REM sleep can suggest a condition such as narcolepsy and idiopathic hypersomnia. The Multiple Sleep Latency Test (MSLT) is often used to diagnose these conditions. The MSLT involves taking a series of 20-minute naps every two hours, and the time it takes to fall asleep and reach REM sleep is measured. Sleep latency is defined as the time from lights out to N1, and usually, sleep latency is less than 20 minutes.