Validation of the Brazilian Portuguese version of the Pittsburgh Sleep Quality Index

Abstract 

Introduction

The Pittsburgh Sleep Quality Index (PSQI) is a questionnaire that assesses sleep quality and disturbances over a 1-month period. It is a valuable tool for research purposes. The aim of this study was to validate a Brazilian Portuguese version of the PSQI.

Methods

The Brazilian Portuguese version (PSQI-BR) was developed according to the following steps: (a) translation, (b) back-translation, (c) comparison between translation and back-translation performed by a group of experts, and (d) pretest in bilingual individuals. Between January 2006 and September 2007, the PSQI-BR was applied to a group of consecutive patients who were submitted to overnight polysomnography with clinical suspicion of obstructive sleep apnea syndrome (OSAS) or insomnia. As in the original article, a group of patients with depression and a control group were included. The depression group was composed of patients from the Mood Disorders Unit of the Psychiatry Department of Hospital de Clínicas de Porto Alegre (HCPA), Brazil. The control group was composed of subjects with a history of normal sleep habits, without noticed snoring.

Results

A total of 83 patients and 21 controls completed the questionnaire and were submitted to overnight polysomnography. The seven-component scores of the PSQI-BR had an overall reliability coefficient (Cronbach’s α) of 0.82, indicating a high degree of internal consistency. The groups included 43 patients with OSAS, 21 with insomnia, 19 with depression and 21 controls. The mean (±SD) PSQI-BR score was 8.1±4.0 for patients with OSAS, 12.8±3.7 for insomnia patients, 14.5±3.7 for those with depression and 2.5±2.0 for control subjects. The one-way ANOVA demonstrated significant differences in PSQI-BR scores across the four diagnostic groups (p<0.001). Post hoc tests between paired groups showed that scores for OSAS, depression and insomnia were significantly higher than for controls (p<0.05). PSQI-BR scores for insomnia did not differ from those obtained for depression (p>0.05), but both were higher than for OSAS (p<0.05).

Conclusions

The results of the present study demonstrate that the PSQI-BR is a valid and reliable instrument for the assessment of sleep quality and equivalent to its original version when applied to individuals who speak the Brazilian Portuguese language. Despite relevant influences of language and cultural background, no major cultural adaptations were necessary during the validation process. The PSQI-BR can be a tool either for clinical management or research.

Keywords: Sleep quality, Pittsburgh Sleep Quality Index, Validation studies, Cultural adaptation, Sleep disorders, Sleep questionnaires