Abstract
Sleep efficiency is a widely used indicator of sleep quality in actigraphy studies. Nevertheless, it isa composite metric integrating data derived from actigraphic recordings alongside informationabout bedtime and wake-up time, typically obtained from self-reported sleep logs. The aim of thisreport is to propose a novel sleep efficiency index, denoted as core sleep efficiency, that reliessolely on actigraphic data and focuses on the quality of sleep after its onset. Using a database ofactigraphic recordings obtained in 40 young subjects (22 ± 3 yrs, Mean±SD) and in 45 middle-agedsubjects (63 ± 11 yrs, Mean±SD), we evaluated the interrelationship between the two metrics ofsleep efficiency and investigated the extent of their correlation with other crucial actigraphicindicators of sleep quality, such as sleep onset latency, fragmentation index and mean activityscore. We provided evidence suggesting that the novel index may be suitable for specificallyassessing the quality of sleep once it has begun. We propose that the newly introduced core sleepefficiency has the potential to serve as a valuable adjunct to the classic sleep efficiency, thusenriching the parametric characterisation of sleep obtained through actigraphy.