Sleep efficiency is usually measured by polysomnography, but can also be measured with physical activity monitors. It is the ratio of time spent lying down in bed to actual time spent asleep. I have been looking through the literature and found one paper that considers 85% and higher as normal, while another considered 90% and higher as normal/good sleep efficiency. Wikipedia says 85-90%. If anyone has a reliable source as to which cut-off is used more commonly please let me know. Thanks.
Hello Samannaaz,
Sleep efficiency is one of the variables that have been defined to help characterize the quality, composition, and quantity of sleep. Any condition that results in frequent or prolonged awakenings results in an increased wake after sleep onset (WASO). Even if WASO is small, it is possible to have low sleep efficiency if the final awakening occurs early in the monitoring period by polysomnography. In such situation, total sleep time (TST)/total time in bed (TIB) is reduced, even though TST/ sleep period time (SPT) is normal. The normal ranges of several parameters which are used to calculate of sleep efficiency (i.e., time in bed, sleep period time, sleep latency, etc.) are not only sex-, and age-dependent, but also remain subject of individual variability. While there are published population-based accepted normative values for sleep architecture parameters, they are the mean plus-minus standard deviation. There also remain issues in the standardization of the current protocol of how sleep efficiency calculates.
Kind regards,
Tatyana
References:Williams RL, Karacan I, Hursch CJ. Electroencephaly (EEG) of human sleep:clinical applications. New York, John Wiley &Sons, 1974; 49-60.
I agree with earlier responses stating that 85% is the generally accepted cut-off for "normal" sleep efficiency; however, I think it is important to mention that the population you are measuring matters. Older adults, for instance, would typically have much lower sleep efficiency.
Article Measuring sleep quality in older adults: A comparison using ...
According to the Pittsburgh Sleep Quality Index, sleep efficiency is considered normal 85% or more.
Going through this question myself and hard to find a semi-decent reference other than some authors are linking to other studies which used 85% as a criterion. Here is one example: https://academic.oup.com/sleep/article/38/6/877/2416970
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