Reliability and initial validation of the Pittsburgh Sleep Quality Index, European Portuguese version: A preliminary study in a sample of higher education students

Abstract

The Pittsburgh Sleep Quality Index (PSQI) is probably the most used self-response scale to measure sleep quality worldwide. However, surprisingly, in our country we are still lacking data on the metric characteristics of the European Portuguese version of this tool, which limits its use both in research and especially in clinical practice. The aim of the present study was thus to examine the psychometric properties of the official European Portuguese (PT) version of the PSQI. After having Dr. Buysse (U. Pittsburgh) permission to use the European Portuguese version of the PSQI, we recruited a sample of 355 undergraduates and master degree students of both sexes, who completed a set of demographic questions, selected items from a previously validated undergraduate sleep-wake questionnaire containing a Sleep Quality Index (SQI), and the PSQI [PT]. The reliability coefficients concerning internal consistency were satisfactory: Cronbach’s alpha = .65 for the PSQI [PT] components, and .74 considering the PSQI [PT] items. Comparing groups who did versus who did not consider having any sleep problems, the formers obtained significantly higher scores in all items of the PSQI [PT], meaning poorer sleep quality, which supports the discriminative power of each item. The computation of the cut-off point using ROC curve for this sample was 6, which is similar to the one found in the original study (i.e., 5). The PSQI [PT] scores were significantly correlated with the SQI (Spearman rs = .59; p < 0.001), which indicates convergent validity. The official European Portuguese version of the PSQI, despite its limitations, seems to be an instrument with adequate reliability and validity for assessing self-reported sleep quality, at least in Portuguese higher education students. However, it is necessary to replicate these analyses using larger and clinical samples. We are grateful to Dr. Buysse (U. Pittsburgh) for the permission to use the European Portuguese version of the PSQI. Thanks are also due to the Department of Education of the University of Aveiro, which supported the printed materials for data collection.