title: Suitability of the Epworth Sleepiness Scale (ESS) for Economic Evaluation: An Assessment of Its Convergent and Discriminant Validity.
abstract: 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]).
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.
authors.affiliation: a Health Economics Unit, School of Medicine, Flinders University , Adelaide , Australia.
authors.forename: Billingsley
authors.initials: B
authors.lastname: Kaambwa
authors.affiliation: a Health Economics Unit, School of Medicine, Flinders University , Adelaide , Australia.
authors.forename: Christine
authors.initials: C
authors.lastname: Mpundu-Kaambwa
authors.affiliation: b The Health Observatory, Discipline of Medicine, University of Adelaide , Adelaide , Australia.
authors.forename: Robert
authors.initials: R
authors.lastname: Adams
authors.affiliation: b The Health Observatory, Discipline of Medicine, University of Adelaide , Adelaide , Australia.
authors.forename: Sarah
authors.initials: S
authors.lastname: Appleton
authors.affiliation: c Freemasons Foundation Centre for Men's Health, School of Medicine, University of Adelaide , Adelaide , Australia.
authors.forename: Sean
authors.initials: S
authors.lastname: Martin
authors.affiliation: c Freemasons Foundation Centre for Men's Health, School of Medicine, University of Adelaide , Adelaide , Australia.
authors.forename: Gary
authors.identifier: 0000-0001-6818-6065
authors.initials: G
authors.lastname: Wittert
mesh_terms: D000328:Adult; D000368:Aged; D003362:Cost-Benefit Analysis / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D000077260:Sleepiness; D011795:Surveys and Questionnaires