Reliability and validity of the simplified Chinese version of Epworth sleepiness scale

Objective To investigate the reliability and validity of the simplified Chinese version of Epworth sleepiness scale（ESS）. Methods Five hundred and eighty-five patients with suspected obstructive sleep apnea hypopnea syndrome （OSAHS） and 103 OSAHS patients who underwent operations were included in this study. The ESS was filled before polysomnography （PSG） monitoring under the direction of professional technicians. The patients who underwent operations did both PSG and ESS tests more than 6 months after operation. Fifty-one patients who underwent PSG at our hospital from July to August, 2010 were chosen to assess the ESS test-retest reliability on two separate occasions at least more than one week. Results The total Cronbach's Alpha of ESS was 0. 814. The test-retest reliability of ESS total scores was 0.679 and for each item was from 0.473 to 0.698 （P < 0.01）. Split-half reliability was 0.817 （P < 0.01）. In the analysis of discriminant validity with apnea hypopnea index （AHI）, the ESS total scores and each item's scores had significant differences in severity in OSAHS patients and simple snoring patients（P < 0.05）, and this was also true in different degrees of lowest saturation of arterial oxygen （LSaO2） patients and normal LSaO2 patients（P<0.05）. The factor analysis of construct validity showed that 4 factors were extracted.The cumulative proportion was 74.270%. The loading was higher than 0.4 among every item. The correlation coefficiency of overall ESS scores and each item's scores was relatively high except the last item.The ESS had low consistency with clinical diagnosis（κ =0.099,P <0.01） and the predictive validity was not good （r =0.138, P <0.01）. As for 103 patients who had operations, the initial assessment of total ESS scores were 15.0[10;20] （M[P25 ;P75]）,and improved to 4[1;6] after operation. The patients who got effective results had significant difference in the total ESS scores before and after operation （Z = -7.528,P<0.01） ,so was the patients who got ineffective results（Z= -4.382, P<0.01） . Conclusions The simplified Chinese version of ESS had a good reliability and validity. It can be used to evaluate the chance of dozing in the daytime. Key words: Disorders of excessive somnolence; Sleep apnea,obstructive; Questionnaires; Reproducibility of results; Polysomnography