Internal consistency and validity of the Spanish version of the quality of life questionnaire specific for obstructive sleep apnea: sleep apnea quality of life index

Introduction: The objective of the present study was to validate the Spanish version of the SAQLI, which is a health-related quality of life (HRQL) questionnaire specific for sleep apnea-hypopnea syndrome (SAHS), and to assess its sensitivity to change.

Material and methods: A multicenter study performed in a group of patients with SAHS (apnea-hypopnea index [AHI] ≥5) who had been referred to the centers' Sleep Units. All patients completed the following questionnaires: SF-36, FOSQ, SAQLI and Epworth scale. The psychometric properties (internal consistency, construct validity, concurrent validity, predictive value, repeatability and responsiveness to change) of the SAQLI were assessed (four domains: daily function, social interactions, emotional function and symptoms; an optional fifth domain is treatment-related symptoms).

Results: One hundred sixty-two patients were included for study (mean age: 58±12; Epworth: 10±4; BMI: 33±5.9kg m(-2); AHI: 37±15hour(-1)). The factorial analysis showed a construct of four factors with similar distribution to the original questionnaire domains. Internal consistency (Cronbach's alpha between 0.78 and 0.82 for the different domains), concurrent validity for SF-36, Epworth scale and FOSQ, and test-retest reliability were appropriate. The predictive validity of the questionnaire showed no significant correlations with the severity of SAHS. SAQLI showed good sensitivity to change in all the domains of the questionnaire (p<0,01).

Conclusions: The Spanish version of the SAQLI is a valid HRQL measurement with appropriate psychometric properties for use in patients with SAHS and it is sensitive to change.