Insomnia Severity Index
This is a numeric variable with values ranging from 0-28 based on the Sleep Questionnaire II form. Missing if did not answer any of following: SQEA6, SQEA7, SQEA8, SQEA9. If SQEA10 answered “Yes 1,” but any of following missing: SQEA11, SQEA12, SQEA13, then missing. Missing if did not answer SQEA10 and SQEA11-SQEA13.