Psychometric assessment of subjective sleep quality using the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J) in psychiatric disordered and control subjects

Subjective sleep quality has been identified as an important clinical construct in psychiatric disordered patients. The Pittsburgh Sleep Quality Index (PSQI), one of the most widely used standardized measures to assess subjective sleep quality, generates a global score and scores seven components. The present study psychometrically assessed clinical profiles of subjective sleep quality in 82 control and 92 psychiatric disordered subjects (primary insomnia, n=14; major depression, n=30; generalized anxiety disorder, n=24; and schizophrenia, n=24), using the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J). The overall reliability coefficient of the PSQI-J was high (Cronbach's alpha=0.77). Correlation coefficients between the PSQI-J global and component scores were statistically significant. The PSQI-J global and component mean scores were significantly higher in psychiatric disordered subjects than control subjects, except for the component of sleep duration. Using a cut-off point of 5.5 in the PSQI-J global score, estimations of sensitivity and specificity provided 85.7 and 86.6% for primary insomnia, 80.0 and 86.6% for major depression, 83.3 and 86.6% for generalized anxiety disorder, and 83.3 and 86.6% for schizophrenia, respectively. The present study supports the utility of the PSQI-J as a reliable and valid measure for subjective sleep quality in clinical practice and research.