title: Confirmatory factor analysis of the Epworth Sleepiness Scale (ESS) in patients with obstructive sleep apnoea.
abstract: BACKGROUND
  The Epworth Sleepiness Scale (ESS [Johns MW. A new method for measuring daytime sleepiness: the Epworth sleepiness scale. Sleep 1991;14(6):540-5]) has been used frequently to assess daytime sleepiness, particularly in the context of clinical sleep disorders. Its psychometric properties are still unclear, particularly when used to evaluate sleep propensity in patients with obstructive sleep apnoea.
  
  
  METHODS
  The present study used confirmatory factor analysis (CFA) to investigate a potential single-factor structure of the ESS in a sample of 759 Australian patients with a diagnosis of obstructive sleep apnoea by the treating physicians.
  
  
  RESULTS
  CFA results from showed that the original single-factor structure proposed by Johns [Johns MW. Reliability and factor analysis of the Epworth Sleepiness Scale. Sleep 1992;15(4):376-81] did not adequately fit the data. A re-specified single-factor solution provided a good fit for data, and this improved fit was confirmed on a second CFA.
  
  
  CONCLUSIONS
  The findings suggest that standard scoring of the ESS should be interpreted cautiously for patients with obstructive sleep apnoea.
authors.affiliation: School of Psychology, The University of Queensland, St. Lucia, Qld 4072, Australia. ssmith@psy.uq.edu.au
authors.forename: Simon S
authors.initials: SS
authors.lastname: Smith
authors.forename: Tian P S
authors.initials: TP
authors.lastname: Oei
authors.forename: James A
authors.initials: JA
authors.lastname: Douglas
authors.forename: Ian
authors.initials: I
authors.lastname: Brown
authors.forename: Greg
authors.initials: G
authors.lastname: Jorgensen
authors.forename: Jonathan
authors.initials: J
authors.lastname: Andrews
mesh_terms: D000328:Adult; D000368:Aged; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011594:Psychometrics / Q000706:statistics & numerical data; D011793:Queensland; D015203:Reproducibility of Results; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis*; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D010100:Oxygen