The Sleep Impairment Index is a 7 - item scale that yields a quantitative index of insomnia severity; it was used as a collateral measure of treatment outcome.6 Ratings on a 5 - point scale were obtained on the perceived severity of sleep onset, sleep maintenance, and
early morning awakening problems; interference with daytime functioning; noticeability of impairment caused by the sleep problem; distress / concern caused by the sleep problem; and satisfaction with current sleep pattern.