Background: Excessive daytime sleepiness is a frequent symptom and a public health problem due to its association with automobile and work related accidents. The aim of this study was to develop and carry out a preliminary assessment of the Spanish version of the functional outcomes sleep questionnaire and the Epworth sleepiness scale, two instruments designed to evaluate patients with sleep disorders.
Material and methods: For the adaptation, the forward and back-translation method by bilinguals was used with professional and lay panel. Once tested for feasibility and comprehension, 39 patients with obstructive sleep apnea syndrome completed the Spanish version of the FOSQ and the Epworth sleepiness scale, together with a question on self-rated health status.
Results: Difficulty of translation was assessed as low and the naturalness of Spanish expressions as high for all the items of the questionnaires except for the response options of the Epworth sleepiness scale. Both questionnaires showed higher reliability than the standard proposed for individual comparisons (Cronbach's alpha > 0.9). The FOSQ vigilance scale showed a high correlation with the Epworth score (r = -0.79), while for the other scales of the FOSQ correlations were moderate (r ranging from -0.52 to -0.68). Patients who reported "regular" or "poor" health had significantly worse scores for most of the FOSQ scales.
Conclusion: These results suggest that the Spanish versions of both questionnaires are conceptually equivalent to the originals and that they show similar characteristics of reliability and validity. The FOSQ vigilance scale assess daytime sleepiness similarly to Epworth but the others scales of the FOSQ provide additional information for these patients.