The Spanish version of the Insomnia Severity Index: A confirmatory factor analysis

Fernandez-Mendoza, Julio; Rodriguez-Muñoz, Alfredo; Vela-Bueno, Antonio; Olavarrieta-Bernardino, Sara; Calhoun, Susan L.; Bixler, Edward O.; Vgontzas, Alexandros N.

doi:10.1016/j.sleep.2011.06.019

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Volume 13, Issue 2 , Pages 207-210, February 2012

The Spanish version of the Insomnia Severity Index: A confirmatory factor analysis

Julio Fernandez-Mendoza
- Sleep Research and Treatment Center, Department of Psychiatry, College of Medicine, Penn State University, Hershey, PA, USA
- Corresponding author. Address: Sleep Research and Treatment Center, Department of Psychiatry, Penn State College of Medicine, 500 University Drive H073, Hershey, PA 17033, USA. Tel.: +1 7175310003x285570.
Alfredo Rodriguez-Muñoz
- Department of Social Psychology, School of Psychology, Universidad Complutense de Madrid, Spain
Antonio Vela-Bueno
- Department of Psychiatry, School of Medicine, Universidad Autónoma de Madrid, Spain
Sara Olavarrieta-Bernardino
- Department of Psychiatry, School of Medicine, Universidad Autónoma de Madrid, Spain
Susan L. Calhoun
- Sleep Research and Treatment Center, Department of Psychiatry, College of Medicine, Penn State University, Hershey, PA, USA
Edward O. Bixler
- Sleep Research and Treatment Center, Department of Psychiatry, College of Medicine, Penn State University, Hershey, PA, USA
Alexandros N. Vgontzas
- Sleep Research and Treatment Center, Department of Psychiatry, College of Medicine, Penn State University, Hershey, PA, USA

Received 7 March 2011; received in revised form 10 June 2011; accepted 11 June 2011.

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.

Keywords: Insomnia Severity Index, Spanish, Psychometric properties, Confirmatory factor analysis, Validation, Mood, Fatigue