Psychometric assessment of subjective sleep quality using the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J) in psychiatric disordered and control subjects
Introduction
Disturbed subjective sleep quality is an important domain, not only for its high prevalence (Partinen, 1994, Doi et al., 2000), but also for its association with a number of psychiatric disorders (Ford and Kamerow, 1989, Klink et al., 1992, Nofzinger et al., 1993, Ohayon, 1997). Buysse et al. (1989) developed the Pittsburgh Sleep Quality Index (PSQI), a standardized self-administered questionnaire, to assess subjective sleep quality over the previous month and examined its psychometric properties. The PSQI has been widely used for various purposes, as shown in several studies. For example, good subjective sleep quality may be a possible indicator of depressed patients, who would otherwise remain well with interpersonal psychotherapy after discontinuation of pharmacological therapy (Reynolds et al., 1997). Poor subjective sleep quality could be a predictor of suicidal tendency in patients with major depression (Agargun et al., 1997). Subjective sleep quality can be a tool that provides a certain facet of information on the phenomenology of social phobia or panic disorders (Stein et al., 1993a, Stein et al., 1993b). The community-based randomized controlled trials of the effect of exercise on sleep examined subjective sleep quality as an outcome measure in the elderly with sleep complaints or depression (King et al., 1997, Singh et al., 1997).
We developed the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J) after obtaining permission from the original authors of the PSQI (Doi et al., 1998). The goals of our present study were to assess the clinical profiles of subjective sleep quality in psychiatric disordered and control subjects using the PSQI-J, and to provide evidence of some psychometric properties of the PSQI-J by examining its reliability, validity, sensitivity and specificity.
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Subjects
The subjects were 92 psychiatric disordered and 82 control subjects.
The psychiatric disordered subjects were 75 outpatients referred to the Sleep Clinic of the Japanese National Institute of Mental Health (Japanese NIMH) or the Psychiatric Clinic of the Japanese National Center of Neurology and Psychiatry (Japanese NCNP), and 17 sleep disordered subjects who were a subset of our community-based survey on sleep disorder (Doi et al., 1999). Clinical evaluations were carried out on all of the
Subjects
The means and standard deviations of age in each group were as follows: 38.8±12.2 years for control subjects; 50.4±14.6 years for subjects with primary insomnia; 47.0±16.3 years for subjects with major depression; 40.9±15.8 years for subjects with generalized anxiety disorder; and 29.3±9.4 years for subjects with schizophrenia. One-way ANOVA indicated a significant difference in age among the groups (F=8.07, d.f.=4, P<0.001). Compared with control subjects, subjects with primary insomnia, major
Discussion
The present study describes subjective sleep quality in psychiatric disordered and control subjects using the PSQI-J in Japanese subjects and examines its reliability and validity. The findings of the current study replicate a previous study (Buysse et al., 1989); the PSQI-J represents a high degree of internal homogeneity and a good ability to discriminate psychiatric disordered from control subjects with respect to subjective sleep quality. The present findings also suggest considerations
Acknowledgements
This research was supported in part by a Grant on Sleep from the Science and Technology Agency, National Government of Japan. The authors thank the participants and psychiatrists who co-operated in this study, and Dr Toshiro Tango at the Department of Epidemiology, Japanese National Institute of Public Health, for statistical advice.
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