Psychiatry Investig.
2024 Jan;21(1):9-17. 10.30773/pi.2023.0189.
Psychometric Properties of the Insomnia Severity Index and Its Comparison With the Shortened Versions Among the General Population
- Affiliations
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- 1Department of Psychiatry, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
- 2Department of Psychology, University of Chittagong, Chattogram, Bangladesh
- 3National Centre for Epidemiology and Population Health, Australian National University, Canberra, Australia
- 4Department of Psychiatry, Veteran Health Service Medical Center, Seoul, Republic of Korea
- 5Department of Psychiatry, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
- 6Department of Psychiatry, Nowon Eulji University Hospital, Eulji University School of Medicine, Seoul, Republic of Korea
- 7Department of Psychiatry, Chosun University Hospital, College of Medicine, Chosun University, Gwangju, Republic of Korea
- 8Department of Psychiatry, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea
- KMID: 2551063
- DOI: http://doi.org/10.30773/pi.2023.0189
Abstract
Objective
The aim of this study was to explore the psychometric properties of the Insomnia Severity Index (ISI) based on modern test theory, such as item response theory (IRT) and Rasch analysis, with shortened versions of the ISI among the general population.
Methods
We conducted two studies to evaluate the reliability and validity of the shortened versions of the ISI in a Korean population. In Study I, conducted via online survey, we performed an exploratory factor analysis (n=400). In Study II, confirmatory factor analysis (CFA) was conducted (n=400). IRT and Rasch analysis were performed on all samples. Participants symptoms were rated using the ISI, Dysfunctional Beliefs and Attitudes about Sleep–16 items, Dysfunctional Beliefs about Sleep–2 items, Patient Health Questionnaire–9 items, and discrepancy between desired time in bed and desired total sleep time.
Results
CFA showed a good fit for the 2-factor model of the ISI (comparative fit index=0.994, Tucker–Lewis index=0.990, root-meansquare-error of approximation=0.039, and standardized root-mean-square residual=0.046). The 3-item versions also showed a good fit for the model. All scales showed good internal consistency reliability. The scale information curve of the 2-item scale was similar to that of the full-scale ISI. The Rasch analysis outputs suggested a good model fit.
Conclusion
The shortened 2-factor ISI is a reliable and valid model for assessing the severity of insomnia in the Korean population. The results are needed to be explored further among the clinical sample of insomnia.
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