Validation and cutoff score for the single-item sleep quality scale

The Sleep Quality Scale (SQS) is a popular single-item measure of sleep quality that has been used in research and clinical settings. The aim of the current paper is to validate the SQS and provide a cutoff score.

We conducted two studies to validate the SQS and provide a cutoff score to simplify the interpretation of SQS scores. We collected data from 747 physicians and nurses working in Oman.

In Study 1, conducted during the first two weeks of April 2020, a significant positive relationship was observed between the SQS and The World Health Organization Wellbeing Index (r. = 0.90) and a significant negative relationship was found with the Generalized Anxiety Disorder scale (r = .88) and the Intolerance of Uncertainty Scale-12 (r = .88). In Study 2, conducted between October 12 and November 19, 2020, we proposed a cutoff score for the SQS using the Insomnia Severity Index cutoff score of ≥ 10. The estimated area under the receiver operating characteristics curve was 0.881 (95% CI = 0.84-0.92). A cutoff score of ≤ 6 was identified with a sensitivity of 87.50 (95% CI = 0.78-0.94), and a specificity of 74.10 (95% CI = 0.67-0.81).

The findings of this study suggest that the single-item SQS is valid and an acceptable substitute for longer scales for initial assessment of sleep quality. The suggested cutoff value should help in easily classifying individuals into poor sleepers and good sleepers.