Objectives: The aims of this study were to determine (1) the agreement in Epworth Sleepiness Scale (ESS) evaluated by patients and their close relatives (CRs), and (2) the correlation of objective sleepiness as measured by multiple sleep latency test (MSLT) with self-evaluated and close relative-evaluated ESS.
Methods: A total of 85 consecutive patients with obstructive sleep apnea (OSA) (70 males, age 46.7 ± 12.9 years old) with an apnea-hypopnea index (AHI) > 5 events per hour (mean 38.9 ± 26.8/h) were recruited into this study. All participants underwent an overnight polysomnographic assessment (PSG), MSLT, and ESS rated by both patients and their CRs. Mean sleep latency < 8 min on MSLT was considered objective daytime sleepiness.
Results: Self-evaluated global ESS score (ESSG) was closely correlated with evaluation by CRs (r = 0.79, p < 0.001); the mean ESSG score evaluated by patients did not significantly differ from that evaluated by CRs (p > 0.05). However, Bland- Altman plot showed individual differences between self-evaluated and CR-evaluated ESS scores, with a 95%CI of -9.3 to 7.0. The mean sleep latency on MSLT was significantly associated with CR-evaluated ESSG (r = -0.23, p < 0.05); significance of association with self-evaluated ESSG was marginal (r = -0.21, p = 0.05).
Conclusions: CR-evaluated ESS has a good correlation but also significant individual disagreement with self-evaluated ESS in Chinese patients with OSA. CR-evaluated ESS performs as well as, if not better than, self-evaluated ESS in this population when referring to MSLT.
Keywords: Epworth Sleepiness Scale; Obstructive sleep apnea; close relatives; excessive daytime sleepiness; multiple sleep latency test.