Sleep Latency: Definition, Testing, Results

Sleep latency, also known as sleep onset latency or SOL, is the amount of time it takes to fall asleep when you go to bed. Ideally, it should take between 10 minutes and 20 minutes.

Your sleep latency relates directly to sleep efficiency (the quality of your sleep) and sleep debt (how "behind" on sleep you are). An ideal sleep latency period lays the foundation for a solid night's sleep.

Sleep Latency's Relation to Sleep Efficiency

Sleep latency is related directly to sleep efficiency. That's because if you're able to fall asleep quickly, you're more likely to have efficient sleep. The two go hand in hand.

Sleep specialists take the amount of time you spend asleep by the total time you spent in bed, then multiply it by 100. That gives them a percentage that's used to gauge your sleep efficiency.

• 90% or higher = extremely good
• 85% = normal
• Below 85% = poor

Sleep Latency and the Sleep Cycle

An ideal sleep latency lays the foundation for a solid night's sleep, which occurs in two basic states throughout the night. The two stages of sleep that occur throughout the night are rapid eye movement sleep (REM) and non-rapid eye movement sleep (NREM).

REM sleep is a deeper form of sleep than most NREM sleep, but both states are directly impacted by sleep latency. If you have good sleep latency, you'll have a better chance of progressing through the stages of sleep comfortably and, in turn, enjoy a night of deep sleep.

The Impact of Sleep Debt on Sleep Latency

Sleep debt is the overall effect of not getting enough sleep. Sleep debt can accumulate over time and, in turn, lead to mental and physical fatigue.

Sleep debt has a direct impact on sleep latency, since having a lot of sleep debt makes you extremely tired, meaning you'll likely fall asleep faster than someone who doesn't have any sleep debt.

Many factors determine your sleep latency, and overall sleep debt is a big one. Falling asleep almost immediately upon laying down is often a sign of sleep debt and, therefore, a sign that you should try to get more sleep on a nightly basis.