title: The Spanish version of the Insomnia Severity Index: a confirmatory factor analysis.
abstract: OBJECTIVE
  To examine the psychometric properties of the Spanish version of the Insomnia Severity Index (ISI) and to determine its factor structure with confirmatory factor analysis (CFA).
  
  
  METHODS
  Self-reported information was collected from a sample of 500 adults (mean age 39.13 [standard deviation 15.85]years) drawn from a population of medical students and their social networks. Together with the ISI, a measure of the subjective severity of insomnia, subjects completed the Pittsburg Sleep Quality Index, the Epworth Sleepiness Scale, and the Profile of Mood States to study concurrent validity of the ISI. CFA was used to test alternative models to ascertain the factorial structure of the ISI.
  
  
  RESULTS
  The Spanish version of the ISI showed adequate indices of internal consistency (Cronbach's α=0.82). CFA showed that a three-factor structure provided a better fit to the data than one-factor and two-factor structures. The ISI was significantly correlated with poor sleep quality, fatigue, anxiety, and depression, and discriminated between good and poor sleepers.
  
  
  CONCLUSIONS
  The ISI is a reliable and valid instrument to assess the subjective severity of insomnia in Spanish-speaking populations. Its three-factor structure (i.e., night-time sleep difficulties, sleep dissatisfaction and daytime impact of insomnia) makes it a psychometrically robust and clinically useful measure.
authors.affiliation: Sleep Research and Treatment Center, Department of Psychiatry, College of Medicine, Penn State University, Hershey, PA 17033, USA. jfernandezmendoza@hmc.psu.edu
authors.forename: Julio
authors.initials: J
authors.lastname: Fernandez-Mendoza
authors.forename: Alfredo
authors.initials: A
authors.lastname: Rodriguez-Muñoz
authors.forename: Antonio
authors.initials: A
authors.lastname: Vela-Bueno
authors.forename: Sara
authors.initials: S
authors.lastname: Olavarrieta-Bernardino
authors.forename: Susan L
authors.initials: SL
authors.lastname: Calhoun
authors.forename: Edward O
authors.initials: EO
authors.lastname: Bixler
authors.forename: Alexandros N
authors.initials: AN
authors.lastname: Vgontzas
mesh_terms: D000328:Adult; D000339:Affect; D001007:Anxiety / Q000209:etiology / Q000523:psychology; D003863:Depression / Q000209:etiology / Q000523:psychology; D005221:Fatigue / Q000209:etiology / Q000523:psychology; D006801:Humans; D007802:Language; D008875:Middle Aged; D011594:Psychometrics / Q000379:methods* / Q000592:standards*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications* / Q000523:psychology*