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Journal of Psychosomatic Research 53 (2002) 737 – 740

Test–retest reliability and validity of the Pittsburgh Sleep Quality Index in primary insomnia Jutta Backhausa,*, Klaus Junghannsa, Andreas Broocksa, Dieter Riemannb, Fritz Hohagena a b

Department of Psychiatry and Psychotherapy, University Hospital of Luebeck, Luebeck, Germany Department of Psychiatry and Psychotherapy, University Hospital of Freiburg, Freiburg, Germany Received 19 July 2001; accepted 5 February 2002

Abstract Objective: Psychometric evaluation of the Pittsburgh Sleep Quality Index (PSQI) for primary insomnia. Methods: The study sample consisted of 80 patients with primary insomnia (DSM-IV). The length of the test – retest interval was either 2 days or several weeks. Validity analyses were calculated for PSQI data and data from sleep diaries, as well as polysomnography. To evaluate the specificity of the PSQI, insomnia patients were compared with a control group of 45 healthy subjects. Results: In primary insomnia patients, the overall PSQI global score correlation coefficient for test – retest reliability was .87. Validity analyses showed high correlations between PSQI and sleep log data and lower correlations with polysomnography data. A PSQI global score > 5 resulted in a sensitivity of 98.7 and specificity of 84.4 as a marker for sleep disturbances in insomnia patients versus controls. Conclusion: The PSQI has a high test – retest reliability and a good validity for patients with primary insomnia. D 2002 Elsevier Science Inc. All rights reserved.

Keywords: Pittsburgh Sleep Quality Index; Primary insomnia; Sleep; Reliability; Validity

Introduction Since its introduction in 1989, the Pittsburgh Sleep Quality Index (PSQI) [1] has gained widespread acceptance as a useful tool to measure sleep quality in different patient groups (for overview of sleep questionnaires, see Refs. [2,3]). Its good reliability and validity could be shown for patients with psychiatric and sleep disorders [1,4], for patients with different somatic diseases [5], for nursing home residents [6], and for healthy elderly subjects [7], whereas data on its validity and reliability for primary insomnia are scarce. Primary insomnia is a sleep disorder that is caused neither by an organic nor by any other psychiatric disorder. There is a chronic difficulty in initiating or maintaining sleep, which causes clinically significant distress or impairment in social, occupational, or other important areas of functioning. Doi et al. [4] evaluated the reliability of a Japanese version of the PSQI in a sample of psychiatric patients, which included * Corresponding author. Klinik fur Psychiatrie und Psychotherapie, ¨ Universitaetsklinikum Luebeck, Ratzeburger Allee 160, D-23538 Luebeck, Germany. Tel.: +49-451-500-2922; fax: +49-451-500-2603. E-mail address: (J. Backhaus).

a small subsample of 14 patients with primary insomnia. They found a high reliability with an overall Cronbach’s alpha of .77 (n = 14). There are no data published yet on test – retest reliability and validity of the PSQI with sleep logs for patients with primary insomnia. The study presented here serves this goal.

Methods PSQI The PSQI is a self-rating questionnaire resulting in a global score between 0 and 21, which consists of seven subscores (see Table 1). The questionnaire is easy to handle and can be completed within 5 min. The whole questionnaire is published by Buysse et al. [1]. The German version has been translated from English into German and then retranslated for comparison with the original version. In the German version, the estimate period was reduced from 4 to 2 weeks [8], because the German PSQI served as an instrument to evaluate a short-term therapy for primary insomnia [9], for which the 4-week period seemed too long.

0022-3999/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 2 2 - 3 9 9 9 ( 0 2 ) 0 0 3 3 0 - 6...
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