Circadian rhythm : Influence on Epworth Sleepiness Scale score

Abstract

The Epworth Sleepiness Scale (ESS) is frequently used to determine daytime sleepiness in patients with sleep-disordered breathing. It is still unclear whether different levels of alertness induced by the circadian rhythm influence ESS score. The aim of this study is to investigate the influence of circadian rhythm-dependent alertness on ESS performance. In amonocentric prospective noninterventional observation study, 97patients with suspected sleep-disordered breathing were investigated with respect to daytime sleepiness in temporal relationship to polysomnographic examination and treatment. The Karolinska Sleepiness Scale (KSS) and the Stanford Sleepiness Scale (SSS) served as references for the detection of present sleepiness at three different measurement times (morning, noon, evening), prior to and following adiagnostic polysomnography night as well as after acontinuous positive airway pressure (CPAP) titration night (9measurements in total). The KSS, SSS, and ESS were performed at these times in arandomized order. The KSS and SSS scores revealed acircadian rhythm-dependent curve with increased sleepiness at noon and in the evening. Following adiagnostic polysomnography night, the scores were increased compared to the measurements prior to the night. After the CPAP titration night, sleepiness in the morning was reduced. KSS and SSS reflect the changes in alertness induced by the circadian rhythm. The ESS score war neither altered by the intra-daily nor by the inter-daily changes in the level of alertness. According to the present data, the ESS serves as areliable instrument to detect the level of daytime sleepiness independently of the circadian rhythm-dependent level of alertness.