The Reliability and Validity of the Persian Version of Pittsburgh Sleep Quality Index in Iranian People

Sleep disturbances are a significant public health issue and such problems are associated with a number of psychiatric disorders. The Pittsburgh Sleep Quality Index (PSQI) is an effective instrument frequently used to evaluate sleep style and quality. The present study aimed to assess the reliability, validity, and factor structure of the Persian version of PSQI. This cross-sectional study was conducted on 1115 citizens of Arak City, Iran aged 18-60 years. They were selected by stratified random sampling method from different parts of the city. The following aspects of the Persian version of PSQI were evaluated to assess its validity and reliability. To assess the validity of the content, the questionnaire was sent to a panel of 15 academic members consisting of experts in the fields of psychology and health education. The internal consistency of the PSQI questionnaire was evaluated by the Cronbach alpha coefficient and item-scale correlation. To investigate the factor structure of the PSQI, Exploratory Factor Analysis (EFA) was performed with a 2-factor solution and varimax rotation. The extraction of principal factors was performed after varimax orthogonal rotation and Kaiser’s criterion. At last, Confirmatory Factor Analysis (CFA) was applied to assess the reliability of the PSQI questionnaire. All analyses were performed in SPSS V. 16.0 and AMOS for Windows. The Persian version of PSQI was evaluated in the study with regard to its internal consistency and factor structure. The result showed excellent item content validity index (≥0.78) and excellent scale content validity index (≥0.90). The result of the Cronbach alpha coefficient was 0.65. The factors of perceived sleep quality and sleep efficiency were extracted by means of factor analysis and these two factors explained 51.75% of the total variance. Confirmatory factor analysis results show the model’s satisfactory fitting based on adequacy criteria goodness of fit index, goodness of fit index adjusted for degrees of freedom, root mean square error of approximation, and comparative fit index. The non-normed fit index was close to its reference value of 0.90. In general, findings suggest that the Persian version of PSQI displayed satisfactory validity and reliability to measure the quality of sleep of Iranian people, at least citizens of Arak City, Iran.