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

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

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).

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).

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.