Psychometric analysis of Epworth Sleepiness Scale and its correlation with Pittsburgh sleep quality index in poor sleepers among Indian university students

Abstract

Background The Epworth Sleepiness Scale (ESS) is an 8-item scale to detect excessive daytime sleepiness. Although its psychometric properties are well established on a number of populations the same has not been done for an Indian population, hence this study was designed to cover this knowledge gap. Aims The purpose of this study was to establish the test-retest reliability, validity and internal consistency of the ESS and its correlation with the Pittsburgh Sleep Quality Index (PSQI) in poor sleepers in India. Materials and methods Twenty-five poor sleepers were randomly chosen from a university population. All the subjects were administered the two scales on the test day and the same was repeated after 1 week, which was the retest. Statistical analysis Intraclass coefficient (ICC) and standard error of measurement (SEM) were calculated for the reliability which was further supported by the Bland-Altman graph and a scatterplot. Cronbach's alpha and Pearson's coefficient were calculated for internal consistency and correlation, respectively. Results Twenty-five poor sleepers with mean age 25.24 ± 7.04 years were recruited. The test-retest reliability for ESS displayed good reliability (ICC2,1: 0.86) which was supported by the Bland-Altman graph and the scatterplot. Cronbach's alpha was reported as 0.86 and Pearson's coefficient was r: 0.62, p-value: 0.001. Conclusion The results suggest that the ESS has good internal consistency and test-retest reliability for a university population of poor sleepers in India.

Keywords: Epworth Sleepiness Scale; Indian university population; Pittsburgh Sleep Quality Index; excessive daytime sleepiness; poor sleepers.