The ISI comprises seven items that evaluate difficulty falling asleep and staying asleep, problems waking up too early, satisfaction with current sleep patterns, interference with daily functions, noticeability of impairment attributed to sleep problems, and distress caused by the sleep problem. Each of the ISI items is rated on a scale of 0-4; the total score ranges from 0 to 28, with a higher score indicating greater insomnia severity. The total ISI scores are divided into four subcategories: 0-7, no clinically significant insomnia; 8-14, subthreshold insomnia; 15-21, moderate insomnia; and 22-28, severe insomnia. A cutoff score of 15 has been used as the threshold for clinically significant insomnia, and a score below 8 has been used to define remission after treatment (i.e., no longer meets the criteria for insomnia).28 (link)
Linguistic validation was achieved by having two sleep specialists translate the original ISI questionnaire into Korean; the Korean version was then translated back into English by one sleep specialist and one linguist, both of whom were fluent in Korean and English. Comparison of the original ISI with the final back-translated version was performed by individuals who were fluent in both languages and who were not involved in the research study. The final ISI-K was obtained after completion of these standard procedures.
Linguistic validation was achieved by having two sleep specialists translate the original ISI questionnaire into Korean; the Korean version was then translated back into English by one sleep specialist and one linguist, both of whom were fluent in Korean and English. Comparison of the original ISI with the final back-translated version was performed by individuals who were fluent in both languages and who were not involved in the research study. The final ISI-K was obtained after completion of these standard procedures.
