Development and validation of the Nonrestorative Sleep Scale (NRSS)

Abstract

Study Objectives: Nonrestorative sleep (NRS) is defined as the subjective feeling that sleep has been insufficiently refreshing, often despite the appearance of physiologically normal sleep. While NRS has been shown to be associated with a variety of cognitive, affective, and medical complaints, there is currently no valid, reliable instrument available in the public domain for its assessment. The purpose of this study was to develop and validate the Nonrestorative Sleep Scale (NRSS). Participants: The scale was administered to a sample of 226 (age: 46.7 ± 14.9 years; gender: 48% female) consecutive sleep clinic patients and to 30 control participants (age: 36.9 ± 12.5; gender: 53% female). Results: Data screening led to a final instrument of 12 items, and factor analysis resulted in 4 factors accounting for 73.2% of total variance. The scale demonstrated excellent internal reliability (α = 0.88) and good test-retest reliability (r = 0.72). Preliminary evaluations of construct validity found that certain subscales correlated reasonably well with previously validated sleep, alertness, and affective scales. Comparisons between global NRSS scores and objective polysomnographic variables revealed a few very small but significant correlations. Conclusions: Based on these findings, the NRSS was confirmed to be a valid and reliable tool for the assessment of nonrestorative sleep.