Sleep efficiency

Sleep efficiency is the percentage of time spent in bed that a person is actually asleep.

It is calculated by dividing total sleep time by total time in bed and multiplying by one hundred. A person who spends eight hours in bed and sleeps for seven has a sleep efficiency of about eighty-eight percent. Values around eighty-five percent or higher are generally considered normal for adults, while lower figures suggest prolonged time falling asleep, extended awakenings or early waking. The measure is a cornerstone of insomnia assessment and of the behavioral therapy that restricts time in bed to match actual sleep.

It can be estimated from a sleep diary or measured objectively with actigraphy or polysomnography, which often disagree because people tend to misjudge how long they lie awake. Sleep efficiency has been reported as an outcome in some cannabinoid sleep studies, with changes that are not consistent across trials.