title: Validation of the three-factor model of the PSQI in a large sample of chronic fatigue syndrome (CFS) patients.
abstract: OBJECTIVE
  To evaluate whether a 3-factor model of the Pittsburgh Sleep Quality Index (PSQI) scale would fit the constellation of sleep disturbances in patients with a diagnosis of chronic fatigue syndrome (CFS).
  
  
  METHODS
  Consecutive CFS patients filled out the PSQI. Scores from this self-report questionnaire were examined with exploratory and confirmatory factor analysis (CFA).
  
  
  RESULTS
  413 CFS patients were included for analysis in this study. CFA showed that the 7 PSQI component scores clustered into the 3 factors reported by Cole et al. (2006), i.e. Sleep Efficiency, Perceived Sleep Quality and Daily Disturbances. In contrast with the single-factor and all 2-factor models, all factor loadings were significant, and all goodness-of-fit values were acceptable.
  
  
  CONCLUSIONS
  In CFS, the PSQI operates as a 3-factor scoring model as initially seen in healthy and depressed older adults. The separation into 3 discrete factors suggests the limited usefulness of the global PSQI as a single factor for the assessment of subjective sleep quality, as also evidenced by a low Cronbach's alpha (0.64) in this patient sample.
authors.affiliation: Department of General Internal Medicine, Infectious Diseases and Psychosomatic Medicine, University Hospital Ghent, Belgium. an.mariman@ugent.be
authors.forename: An
authors.initials: A
authors.lastname: Mariman
authors.forename: Dirk
authors.initials: D
authors.lastname: Vogelaers
authors.forename: Ignace
authors.initials: I
authors.lastname: Hanoulle
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Delesie
authors.forename: Els
authors.initials: E
authors.lastname: Tobback
authors.forename: Dirk
authors.initials: D
authors.lastname: Pevernagie
mesh_terms: D000328:Adult; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D015203:Reproducibility of Results; D012890:Sleep; D012893:Sleep Wake Disorders / Q000175:diagnosis* / Q000523:psychology; D011795:Surveys and Questionnaires