Sleep apnea-hypopnea syndrome (SAHS) is a very prevalent disease in the general population. It is estimated that 4% of men and 2% of women present SAHS with excessive daytime sleepiness, and there is a male/female ratio in the average ages of 2–3/1.1 Health consequences of this chronic sleep alteration and resulting intermittent hypoxemia include neuropsychiatric disorders, cardiovascular morbidity and mortality and the deterioration in quality of life of patients with SAHS.2–5 In order to quantify the variations in the quality of life of patients with SAHS, there are different health-related quality-of-life (HRQL) questionnaires that explore the limitation that this disease causes and how patients feel due to it. These questionnaires should be validated for their use and can be generic or specific. Among the generic questionnaires that have been validated in Spanish is the SF-36,6–8 one of the most widely used and evaluated quality-of-life tools, which, after a decade of use, has been shown to be useful for evaluating HRQL both in the general population as well as in patient groups. In contrast, specific questionnaires have been designed for a certain disease or symptom with the aim to optimize the properties of the tool and, especially, its sensitivity to change. They offer the advantage of being more sensitive for detecting the effects that certain therapeutic interventions have on patients.

Among the specific questionnaires designed for evaluating HRQL in patients with SAHS are the Sleep Apnoea Quality of Life Index (SAQLI)9 and the Québec Sleep Questionnaire (QSQ).10,11 The SAQLI evaluates four HRQL domains: (a) daily functioning; (b) social interactions; (c) emotional functioning; and (d) symptoms. An additional domain of treatment-related symptoms (e) may be added to measure the possible adverse effects of the treatment. The SAQLI, therefore, has the advantage of a section that assesses the response to treatment and its possible adverse effects, which makes it an adequate instrument for carrying out clinical trials and research papers.

Most HRQL questionnaires have been published in English. In order for them to be used in Spanish-speaking countries, a process of translation, transcultural adaptation and validation is required. To date, there are questionnaires validated in Spanish that measure the impact that sleep alterations may have on quality of life, such as the Epworth Sleepiness Scale,12 the Functional Outcomes Sleep Questionnaire (FOSQ)13 or the specific questionnaire for patients with SAHS in the Spanish version of the QSQ.14 The latter has been successfully validated in Spanish by our group. Spanish, with 329 million speakers, is at this time the second most widely spoken language in the world after Chinese (1.213 billion) and before English (328 million).15 SAQLI, which has been validated in Chinese16 and Lithuanian,17 has been translated and successfully adapted to Spanish by our group.18 Although it is true that there is a previous paper validating a Spanish version of the SAQLI that was presented at the 2001 SEPAR congress,19 it had been done in a small number of patients who had not been treated, and therefore the possible negative impact that the SAHS treatment may have had was not analyzed. Given the fact that to date there are no publications in the literature of a version of the SAQLI validated in Spanish that analyses the response to treatment, the objective of our study was to analyze the reliability and the validity of the Spanish version of the HRQL Sleep Apnoea Quality of Life Index in order for it to be used in descriptive and/or evaluative studies in patients with SAHS in Spanish-speaking countries.

During the study period, 216 consecutive patients were sent to the outpatient sleep consultation due to clinical suspicion for SAHS. Twenty-one patients were excluded: 16 presented significant unstable comorbidities (5 hypoventilation-obesity, 7 severe COPD, 2 congestive heart failure, 2 severe arrhythmia); 3 patients were excluded due to important cognitive disorders; and, 2 refused to take part in the study. Out of the 195 patients that were finally included, 162 (83%) were diagnosed with SAHS, and their data were used to analyze the internal consistency and validity of the SAQLI questionnaire. The mean age of these patients was 58±12, with an Epworth scale of 10±4. Mean AHI was 37±15h−1 (range: 5–89), and body mass index (BMI) was 33±5.9kgm−2. The mean overall score of the FOSQ was 86±18, and for the different domains of the SF-36, the scores were: physical functioning, 77±24; physical role functioning, 85±27; bodily pain, 68±33; general health perceptions, 60±19; vitality, 57±21; social role functioning, 86±25; emotional role functioning 88±25, and mental health, 69±19. Out of the patients studied, 133 received CPAP treatment following the SEPAR guidelines. One hundred and seven patients tolerated and complied with a minimum of 4h per day of treatment. Out of the 26 remaining patients treated with CPAP, 13 abandoned the study, 11 did not tolerate the treatment and 2 were lost to the study during the follow-up period (Fig. 1). We found no statistically significant differences in the variables evaluated between the patients that abandoned the study compared with those who did not. Table 1 shows the results referring to the general description of the SAQLI questionnaire (mean, standard deviation, ranges, percentage of patients with ceiling and floor effects).

Fig. 1.

Methodological diagram of the study. *Following SEPAR guidelines. **Validation of the questionnaire. Fifteen patients were randomly chosen for the test–retest reliability. ***A use of ≥4h daily was considered good tolerance. aTwenty-three patients were randomly chosen for the sensitivity-to-change analysis.

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According to our results, the Spanish version of the SAQLI questionnaire presents an internal consistency, validity and repeatability that are adequate for use in SAHS patients. Likewise, this questionnaire has been demonstrated to be sensitive to the change produced by CPAP treatment.

The internal consistency of the tool was high, and the coefficients obtained in each domain surpassed 0.7, which is generally considered acceptable. In the construct validity analysis, we observed a structure similar to that of the original questionnaire. The factor analysis showed, after analyzing the sedimentation chart, that the choice of four factors was similar to the distribution of the SAQLI. These factors explained 42.5% of the variance. In the first factor, referring to daily functioning, 9 out of the 11 items of this domain were included. The second factor only had items pertaining to the social interaction domain. The third and the fourth factors were mostly made up of items corresponding with emotional functioning and symptoms, respectively. Therefore, there is a good correlation between the extracted factors with the domains of the original questionnaire.

When we studied the concurrent validity of the test, we observed that there was a moderate correlation between the daily functioning domain and the score in the vitality, social function and physical role domains of the SF-36. This agrees with the results obtained in the independent validation of the SAQLI, which already demonstrated a moderate correlation with the physical role domain and a strong correlation with the vitality domain of the SF-36.23 The emotional functioning domain presented a strong correlation with the mental health domain of the SF-36 questionnaire and a moderate correlation with the social functioning domain of this same survey. The social interaction domain presented a weak correlation (although somewhat stronger than with the other domains) with social functioning and mental health of the SF-36. The authors of the original validation found a moderate correlation between the Epworth test and the symptoms domain of the SAQLI, although in the validation of the Spanish version both scales presented a weak correlation. Despite the fact that the correlations found between the SAQLI and the related tools of measurement were moderate or weak, it should be emphasized that most of these were statistically significant.

As for the predictive validity of the test, it was not demonstrated that the HRQL was worse in patients with severe SAHS than in those who presented a mild or moderate degree of the disease. This fact has special clinical relevance as it limits its utility in standard clinical practice. In the validation of the QSQ questionnaire done by the authors of the present study, there was an observed worsened HRQL in patients who presented severe SAHS versus mild or moderate SAHS. Therefore, we consider this to be a disadvantage of the SAQLI compared with the QSQ questionnaire, which has been shown to be more appropriate for distinguishing between SAHS severities.

The test–retest reliability demonstrated good agreement in the daily functioning, social interaction and emotional functioning domains, and moderate agreement in the symptoms domain.

In the analysis of the sensitivity to change after CPAP treatment, statistically significant differences were observed in all the domains included in the questionnaire. Nonetheless, the magnitude of change was discretely less than in the original publication,9 obtaining results that were very similar to those reached in the independent validation of the questionnaire done by Lacasse.23 We believe that the explanation of this phenomenon in the original study is due to the fact that the sensitivity to change was studied in a small patient sample effectively treated with CPAP, while both in the independent validation of the original questionnaire as well as in our study, the number of patients was considerably greater. Due to all this, our results support the use of the Spanish version of the SAQLI questionnaire after the application of CPAP treatment.

As for the study limitations, it should be mentioned that a comparative analysis was not done between the capacity for change in those who complied or did not comply with treatment, as well as the size effect, as it is a relatively small sample of individuals. Furthermore, the disappearance of apneas was not confirmed with another sleep test at the end of the study. Nevertheless, we think that these limitations do not compromise the results obtained in the validation.

In conclusion, our validation study indicates that the Spanish version of the SAQLI represents a valid measurement of HRQL and has adequate psychometric characteristics to be used in patients with SAHS when compared with the original questionnaire. Furthermore, it has demonstrated sensitivity to change induced by CPAP treatment.

This article has received the following grants: Valencian Foundation of Pulmonology Grant (2010) and Gasmedi 2000 Grant (2008).

The authors declare having no conflict of interests.