Sleep efficiency measures the time spent asleep versus the time spent laying in bed.

A sleep efficiency score of 85 to 90 percent or greater suggests that you have little trouble falling and staying asleep. Having lower than 80 percent sleep efficiency could suggest sleep problems and an increased mortality risk.

Sleep efficiency is largely unchanged from childhood to adolescence. But research shows it declines in adulthood with the most changes occurring in midlife.

YOU MIGHT STRIVE to go to bed by 9 p.m., hoping to get a good night’s sleep. But if you lie awake for hours before drifting off, your sleep efficiency might be lacking, and it's probably interfering with your ability to get enough rest.

Sleep efficiency refers to the amount of time you spend actually asleep versus the time you spend in bed intending to sleep, says Zachary Strumpf, MD , pulmonary, critical care, and sleep medicine physician at University Hospitals.…