A New Single-Item Sleep Quality Scale: Results of Psychometric Evaluation in Patients With Chronic Primary Insomnia and Depression

Abstract

Study objectives: A single-item sleep quality scale (SQS) was developed as a simple and practical sleep quality assessment and psychometrically evaluated.

Methods: SQS measurement characteristics were evaluated using the Pittsburgh Sleep Quality Index (PSQI) and morning questionnaire-insomnia (MQI) according to prespecified analysis plans in separate clinical studies of patients with insomnia and depression. Patients with insomnia (n = 70) received 4 weeks' usual care with an FDA-approved hypnotic agent; patients with depression (n = 651) received 8 weeks' active or experimental therapy.

Results: Concurrent criterion validity (correlation with measures of a similar construct) was demonstrated by strong (inverse) correlations between the SQS and MQI (week 1 Pearson correlation -.76) and PSQI (week 8 Goodman-Kruskal correlation -.92) sleep quality items in populations with insomnia and depression, respectively. In patients with depression, stronger correlations between the SQS and PSQI core sleep quality components versus other items supported convergent/divergent construct validity (similarity/dissimilarity to related/unrelated measures). Known-groups validity was evidenced by decreasing mean SQS scores across those who sleep normally, those borderline to having sleep problems, and those with problems sleeping. Test-retest reliability (intraclass correlation coefficient) was .62 during a 4-week period of sleep stability in patients with insomnia and .74 in stable patients with depression (1 week). Effect sizes (standardized response means) for change from baseline were 1.32 (week 1) and .67 (week 8) in populations with insomnia and depression, respectively. Mean SQS changes from baseline to week 8 convergently decreased across groups of patients with depression categorized by level of PSQI sleep quality improvement.

Conclusions: The SQS possesses favorable measurement characteristics relative to lengthier or more frequently administered sleep questionnaires in patients with insomnia and depression.

Clinical trial registration: Registry: ClincalTrials.gov, Title: Treatment of Patients With Major Depressive Disorder With MK0869, Identifier: NCT00034983, URL: https://ichgcp.net/clinical-trials-registry/NCT00034983.

Keywords: Morning Questionnaire; Pittsburgh Sleep Quality Index; depression; insomnia; instrument development; psychometric evaluation; sleep; sleep quality scale.

© 2018 American Academy of Sleep Medicine.

Figures

Figure 1. Sleep quality scale instructions.

Figure 2. Anchor-based analysis of clinically meaningful differences at week 8 in patients with depression.

Boxes represent interquartile ranges. Vertical lines represent the minimum data point within the 25th percentile minus 1.5 times the interquartile range and maximum data point within the 75th percentile plus 1.5 times the interquartile range. Horizontal lines within the boxes represent the medians. Diamonds represent means. Dots represent outliers. PSQI = Pittsburgh Sleep Quality Index, SQS = sleep quality scale.