Evaluation of excessive daytime sleepiness in obstructive sleep apnea across international sleep centers

The lack of a definitive measurement of excessive daytime sleepiness (EDS) represents a key challenge in studying this important symptom. The most common approach in research and clinical practice is to utilize the Epworth Sleepiness Scale (ESS), a brief questionnaire measuring the tendency to doze off in eight common situations [1]. However, the ESS correlates poorly with objective tests of EDS and with severity of obstructive sleep apnea (OSA) [2]. Among adults from Iceland [3, 4], we previously applied a multi-dimensional EDS definition including both the ESS (>10 points defined as "risk of dozing") and the question "Do you feel sleepy during the day?" (≥3 times/week defined as "feeling sleepy"). Based on these questions, participants were classified as non-sleepy, risk of dozing only, feeling sleepy only, and presence of both symptoms. In the general population [4] and among OSA patients [3], nearly 25% of subjects reported feeling sleepy during the day despite not having an elevated ESS. Moreover, these patients had significantly lower quality of life and more often reported other sleepiness-related symptoms, insomnia, and evening chronotype [3]. These results suggest that patients experiencing the general feeling of sleepiness without reported risk of dozing (ESS ≤ 10) should still be characterized as having EDS. The aim of this report was to similarly evaluate these four sleepiness phenotypes in a large diverse international cohort. © 2023 Oxford University Press. All rights reserved.