What is sleep onset latency?

Sleep onset latency refers to how long it takes you to fall asleep from the point when you intend to sleep.  On average, a healthy person takes between 10-20 minutes to fall asleep:

• Less than 20 min : Excellent 

• 20-30 min : Fair 

• More than 30 min : Poor

Sleep onset latency is an important measure as it can reflect your overall sleepiness and provide insight into the quality of your sleep. For example, an extremely short sleep onset latency (less than 8 minutes) may indicate extreme sleepiness which could be the result of sleep deprivation, poor sleep or an underlying sleep disorder. On the other hand, taking a long time to fall asleep (more than 20 minutes) may be indicative of insomnia or other factors interfering with your ability to fall asleep. 

Many factors influence sleep onset latency including alcohol (reducing sleep onset latency) and acute or chronic pain (interfering with your ability to fall asleep).  You may further experience variation in sleep onset latency depending on how sleepy you are. For example, if you try to go to bed earlier than usual, it may take you longer to fall asleep since you are not that tired. Conversely, if you stay up later than normal, you are likely to fall asleep quickly, being more tired than usual.