Validation of a Chinese version of the Epworth sleepiness scale

Epworth sleepiness scale ( ESS) is widely used to evaluate degree of somnolence among Chinese patients with sleep- disordered breathing. Yet no Mandarin Chinese translation has ever reported its validation data. In this study we translated and validated the ESS into Mandarin Chinese ( CESS). We found, in 31 bilingual patients responses to the CESS and the English ESS obtained 1 2 weeks apart did not differ significantly (10.5 +/- 3.7 vs. 9.6 +/- 3.9, p = 0.32, Wilcoxon 's signed rank test) and were significantly correlated (Spearman's rho = 0.67, p = 0.0004). A total of 359 sleep- disordered breathing subjects were enrolled into the validation study in a prospective manner. The CESS showed acceptable internal consistency (Cronbach's alpha = 0.81). Thirty out of these patients answered CESS twice at an interval of 2 - 4 weeks, to yield an acceptable level of test -retest reliability (rho = 0.74, p = 0.001). The respiratory disturbance indices obtained from 251 out of 359 subjects were significantly correlated with their CESS scores (rho = 0.22, p < 0 : 001). The standard response mean of CESS was 0.86 as obtained from 94 out of 359 subjects who had initial control of their symptoms at 3 months after radio- frequency palate surgery. We conclude that the CESS is reliable in both a linguistic and a test -retest sense, and appears to be valid and sensitive to clinical change. The CESS could be used to advantage among other Mandarin- speaking subjects as a standardised screening test of sleepiness in daily life.