Validity and reliability of insomnia severity index and its correlation with pittsburgh sleep quality index in poor...

Insomnia severity index (ISI) is a widely used scale in various demographic groups but its psychometric properties have not been established in a sample of Indian subjects. This study was conducted as a preliminary study to extend and confirm the applicability of ISI to an Indian population of university students and to establish its correlation with the Pittsburgh Sleep Quality Index (PSQI).

The study was conducted among the student population of Jamia Millia Islamia, New Delhi, India, with due approval by the institutional ethical committee. Twenty-five poor sleepers with a mean age of 25.24±7.04 years and a BMI of 24.2±2.5 kg/m2 were recruited for the study from the university population. They were administered ISI and PSQI on test day and the same was repeated after 1 week.

The test-retest reliability for ISI (intra-class correlation coefficient, ICC2,1-0.84) was excellent. It was further established by the Bland-Altman graph and scatter plot. The results also showed that ISI (Pearson's coefficient r-0.45) had a strong positive correlation with PSQI. Internal consistency for the ISI (Cronbach's α-0.84) was excellent.

The study findings suggest that ISI has excellent internal consistency, test-retest reliability and validity for the university population of poor sleepers in India. Hence, it can prove to be a good tool for screening insomnia in the current population.