Suitability of the Epworth Sleepiness Scale (ESS) for Economic Evaluation: An Assessment of Its Convergent and Discriminant Validity. Issue 5 (3rd September 2018)

• Record Type: Journal Article
• Authors: Kaambwa, Billingsley; Mpundu-Kaambwa, Christine; Adams, Robert; Appleton, Sarah; Martin, Sean; Wittert, Gary
• Is Part Of: Behavioral sleep medicine. Volume 16:Issue 5(2018)
• Page Start: 448
• Page End: 470
• Publication Date: 2018-09-03
• Subjects: Sleep disorders -- Periodicals; Sleep -- Psychological aspects -- Periodicals; 616.8498
• DOI: 10.1080/15402002.2016.1228647
• Languages: English
• ISSNs: 1540-2002

Abstract

ABSTRACT: Objective : To assess the suitability for use within economic evaluation of a widely used sleep-related instrument (the Epworth Sleepiness Scale [ESS]) by examining its convergent and discriminant validity with two widely used generic preference-based instruments (Short-Form 36 [SF-36] and the Assessment of Quality of Life 4 dimensions [AQoL-4D]). Methods : Data from a cross-section of 2, 236 community-dwelling Australian men were analyzed. Convergent validity was investigated using Spearman's correlation, intraclass correlation, and modified Bland-Altman plots, while discriminant validity was examined using Kruskal Wallis tests. Results : All instruments showed good discriminant validity. The ESS was weakly correlated to the Short Form 6 dimension, or SF-6D (derived from the SF-36) and AQoL-4D utilities ( r = 0.20 and r = 0.19, respectively). Correlations between ESS and SF-36/AQoL-4D dimensions measuring the same construct were all in the hypothesized directions but also weak (range of absolute r = 0.00 to 0.18). The level of agreement between the ESS and AQoL-4D was the weakest, followed by that between the ESS and SF-6D. Moderate convergent validity was seen between the utilities. Conclusions : The lack of convergent validity between the ESS and the preference-based instruments shows that sleep-related constructs are not captured by the latter. The ESS has, however, demonstrated good discriminant validity comparable to that of the AQoL-4D and the SF-36/SF-6D and would therefore be equally useful for measuring subgroup differences within economic evaluation. We therefore recommend using the ESS within cost-effectiveness analysis as a complement to preference-based instruments in order to capture sleep-specific constructs not measured by the latter.