Pittsburgh sleep quality index
This tool was developed by Buysse et al. in 1998 to examine the sleep quality and help identify people with good or poor sleep quality in the general population. This questionnaire contains 18 questions in 7 components. The score of each component is a minimum of 0 and maximum of 3. The sum of the scores of these seven components constitutes the total score of the tool, which ranges from 0 to 21. A score higher than 5 indicates a severe problem in at least two fields or a moderate problem in at least three fields of the questionnaire items. In the study of Buysse et al., the instrument had a sensitivity of 89.6% and specificity of 86.5% in differentiating individuals who sleep well and individuals who sleep poorly. The reliability of PSQI was determined through the test–retest correlation coefficient of 0.85 (