Sleep onset latency, or SOL, is a measurement of the time it takes you to fall asleep once you go to bed, lie down, and turn out the lights. SOL can be an indicator of sleep problems, or let you know that your healthy sleep habits are working. Here’s how sleep onset latency can relate to your sleep habits—and why it matters.
Time to Sleep…
If you fall asleep the second your head hits the pillow (short SOL), you may be sleep deprived or over-tired—or have a hormonal imbalance or other sleep problem that leads you to feel drowsy easily. If, on the other hand, you regularly toss and turn for an hour or more (long SOL), your sleep onset latency is indicative of certain types of insomnia. A very long SOL can also mean that you’re actually getting more sleep than you need, or hypersomnia.
If your SOL varies widely from night to night, check your sleep habits. Are you getting to bed and waking up at regular hours? Are you regularly getting enough sleep? If not, take the time to implement proper sleep hygiene for a few weeks and see if your SOL doesn’t even out.
Healthy Body, Healthy Sleep
Sleep onset latency can also indicate how well your body’s natural sleep-inducing mechanisms are working. If, for example, your body isn’t releasing adequate melatonin or triggering distal vasodilation, your natural tendency to drowsiness after lying down will be interrupted. (Distal vasodilation is just sleep/medical jargon for an expansion of blood vessels in the hands and feet that can lead to cooling body temperatures that trigger the body’s nighttime drowsiness.)
The ability of the SOL to point toward potential problems with sleep habits or potential problems with body chemistry can be both a blessing and a curse. It can be difficult to sort out what’s causing your problems with sleep onset latency—but having your SOL determined in a clinical setting can be a first step to identifying, and then rectifying, your sleep problems.