Reliability and Validity of the Chinese Translation of Insomnia Severity Index and Comparison with Pittsburgh Sleep Quality Index

Background: Insomnia as a symptom can be accompany with many psychological disorders and as a disorder is very common in our clinics. Besides insomnia severity, Index (ISI) is a simple and practical measurement to briefly screen patients with insomnia in clinics and also is a tool to easily assess treatment outcome in research. We aim to determine the reliability and validity of Chinese Translation of Insomnia Severity Index (C-ISI) in patients with Insomnia and compare it with Chinese version of Pittsburgh Sleep Quality Index(C-PSQI). Methods: English version of ISI was translated into Chinese based on standard guidelines then C- ISI was filled in 83 patients with insomnia (clinical group) and 45 persons without sleep complain (as the control group) by themselves.For finding Test-Retest reliability, they refilled ISI questionnaire 2 weeks later. Results: Cronbach’s α coefficient of C-ISI for the clinical group was 0.72, for control groups was 0.75 and for both of them was 0.91. The C-ISI component and total scores in the test were significantly correlated with their related components and total scores in re-test (P < 0.05). Mean Ranks for All C-ISI components, total score were significantly higher inthe clinical group than the controlgroup. There are Significant correlations between C-ISI component and total scores and C-PSQI components and Total scores in related Items. Conclusions: C-ISI is an adequate scale with acceptable reliability and validity and it can evaluate sleep quality in patients with insomnia similar to the PSQI-C so C-ISI  can be used as a good scale to measure sleep quality in Chinese speakers.