Greek version of the Epworth Sleepiness Scale. 
The Epworth Sleepiness Scale (ESS) questionnaire is widely used for the assessment of daytime sleepiness in patients with sleep apnea-hypopnea syndrome (SAHS).  The aim of this study was to develop a Greek version of ESS, bearing in mind that language is a barrier for application in non-English speaking populations.  The forward and backward translation method by bilinguals was applied.  The Greek version of ESS (ESSgr) was then administered to 130 healthy age-matched controls and 211 patients with SAHS with various levels of severity.  Reproducibility of ESSgr and also the sensitivity after continuous positive airway pressure (CPAP) treatment were tested.  Patients' and controls' ESS score was 11.3 +/- 5.1 and 5.6 +/- 3.2, respectively ( p < 0.001).  Total score and individual item score were correlated in both groups.  ESSgr score was correlated with body mass index and apnea-hypopnea index ( p < 0.001) but not with age.  Reproducibility was tested in 29 subjects, revealing no significant difference.  A significant reduction was revealed (14.1 +/- 4.7 vs. 6.4 +/- 3.5; p < 0.001) in 37 patients who were evaluated after CPAP treatment.  Our data validate the ESS for application in Greek-speaking populations.  Despite relevant influences of language and cultural background, ESSgr is a valuable tool for clinical management and research.