What does "WHOOP sleep efficiency" measure or indicate?

WHOOP sleep efficiency is a metric calculated by the WHOOP strap, a wearable fitness and health tracker designed to monitor various physiological markers. Sleep efficiency specifically measures the percentage of time spent in bed that is actually spent sleeping, providing an indication of sleep quality. It is obtained by dividing the total sleep time by the total time spent in bed, then multiplying by 100 to get a percentage. High sleep efficiency suggests that an individual is falling asleep quickly and experiencing fewer disturbances throughout the night, leading to more restorative sleep. Conversely, low sleep efficiency may be an indicator of sleep struggles, such as difficulty falling asleep or waking frequently during the night, and could potentially flag issues that warrant further attention or lifestyle adjustments for better sleep health.