Internal consistency and validity of the Spanish version of the "Quebec Sleep Questionnaire" quality-of-life questionnaire for obstructive sleep apnea

There is no specific health-related quality of life (HRQL) questionnaire that has been validated in Spanish for its use in patients with sleep apnea-hypopnea syndrome (SAHS). The objective of the present study was to validate the Spanish version of the Quebec Sleep Questionnaire (QSQ). A multi-center study including a group of patients with SAHS (AHI≥5) referred to the Sleep Unit. All patients completed the following questionnaires: SF-36, FOSQ, QSQ and Epworth scale. Internal consistency, construct validity, concurrent validity, predictive validity, repeatability and responsiveness to change of the QSQ (32 items in five domains: daytime sleepiness, diurnal symptoms, nocturnal symptoms, emotions, and social interactions) were assessed. A hundred twenty one patients were included in the study (mean age: 57 ± 13; mean Epworth: 9 ± 4; mean Body Mass Index (BMI): 28 ± 3 kg·m(-2) and mean AHI: 36 ± 20 hour(-1)). The factorial analysis showed a construct of five factors with similar distribution to the original questionnaire domains. Internal consistency (Cranach's alpha between 0.78 and 0.93 for the different domains), concurrent validity (compared to SF-36, Epworth scale and FOSQ), predictive validity of SAHS severity and test-retest reliability were appropriate. The test showed good responsiveness to change in diurnal (P=.003) and nocturnal symptoms domains (P=.02). The Spanish version of the QSQ is a valid HRQL measure with appropriate psychometric properties for use in patients with SAHS and is responsive to change in symptoms domains.