The Epworth Sleepiness Scale: translation and validation study of the Iranian version

PURPOSE: The main purpose of this study was to assess the reliability and validity of the Iranian version of the Epworth Sleepiness Scale (ESS-IR).

METHODS: This was a cross-sectional study of 507 suspicious patients either to obstructive sleep apnea (n = 466) or narcolepsy (n = 41) in order to carry out a psychometric evaluation of the ESS-IR by performing reliability, validity, and responsiveness analyses. Reliability of the ESS-IR was assessed by internal consistency and test-retest reliability. Validity of the instrument was assessed using several statistical approaches including construct validity (exploratory factor analysis), discriminant validity, and criterion validity. Responsiveness of the ESS-IR was assessed by comparing the ESS-IR total score before and after 6-9 months of continues positive airway pressure (CPAP) treatment in 16 patients with obstructive sleep apnea (OSA).

RESULTS: The ESS-IR had an acceptable internal consistency and test-retest reliability. Factor analysis in both groups showed a two-factor solution for the ESS-IR, but the first factor showed statistically significant loads in all items. In addition, the ESS-IR discriminated well between patients with and without OSA. There is a fair correlation between the ESS-IR total score and multiple sleep latency test results that is not significant at all. Finally, the ESS-IR was found to be responsive to change where the total score was significantly decreased after CPAP treatment (P < 0.001).

CONCLUSION: The findings suggest that the ESS-IR is a reliable and valid measure for evaluating daytime sleepiness and now can be used in research and clinical settings in Iran.