Assessment of sleep phase, quality, and quantity: the development and validation of the 3-dimensional sleep scale (3DSS).

The 3-Dimensional Sleep Scale (3DSS) is used to assess sleep quality, quantity, and phase. However, its reliability and validity were established using classical methods and it has a small validation sample size. We aimed to increase the sample size and update the statistical methods to validate the reliability and validity of the 3DSS. We conducted a web-based survey of approximately 3000 day-shift workers at four companies in Tokyo, Japan, between 2021 and 2022. The 15 questions in the 3DSS were tested for reliability and validity according to the COSMIN checklist. The maximum likelihood method and promax rotation were selected for exploratory factor analysis. Reliability was tested by calculating the intraclass correlation coefficient and McDonald's ω reliability coefficient. Convergent and discriminant validity were verified using multi-trait multi-method analysis. Cutoff values were verified using receiver operating characteristic curves and area under the curve (AUC). Existing measures used to validate the validity and cutoff values included the Athens Insomnia Scale, social jetlag, weekday sleep duration, and holiday waking time. Overall 2605 participants were included in the analysis after excluding non-responders, non-consenters, and absent employees. Exploratory factor analysis confirmed a three-factor structure for sleep phase, quality, and quantity. For convergent and discriminant validity, ideal correlations were observed for all subscales. The AUCs for sleep phase, sleep quality, and sleep quantity were 0.747, 0.812, and 0.819, respectively. The 3DSS offers sufficient reliability and validity as a sleep assessment scale. An English version of this scale should be developed in the future. Supplementary Information: The online version contains supplementary material available at 10.1007/s41105-025-00600-0.