Psychometric validation of the Ru-SATED 4.0 multidimensional sleep health scale in a representative U.S. sample

STUDY OBJECTIVES: To develop and psychometrically validate a self-report questionnaire assessing multidimensional sleep health among U.S. adults using item response theory (IRT) and classic test theory analyses. METHODS: The Ru-SATED 4.0 scale evaluates 6 sleep health dimensions (Regularity, Satisfaction, Alertness, Timing, Efficiency, Duration). We assessed the scale's comprehensibility with cognitive interviews (n=23) and Lexile analysis. We administered Ru-SATED and other self-reported measures to an adult sample (N=2,000; 18-89y) from the YouGov.com Internet panel, representative of the U.S. population in terms of age, sex, race/ethnicity, and education. We used factor analysis to identify the best combination of 6 items (1 per dimension); calibrated these using IRT Graded Response Models; and examined associations with validated measures to establish construct validity. RESULTS: Cognitive interviews confirmed comprehensibility of the items and response options. The final 6 items had excellent model fit in factor analysis (RMSEA=0.08, SRMR=0.03, CFI=0.97, TLI=0.95). IRT calibration showed individual items varied in their degree of severity assessed (location parameters) and amount of information contributed (discrimination parameters) to overall test scores (θ values). Ru-SATED scores demonstrated moderate internal consistency (r=0.7), convergent validity with other sleep scales (|r|=0.3-0.6), and test-retest reliability (r=0.6) one month later. Ru-SATED scores had smaller correlations with depression/anxiety measures (|r|=0.3-0.4), indicating discriminant validity, and differed significantly among individuals with and without self-reported sleep disorders (Cohen's d=0.93, 95% CI=-1.04-0.81). CONCLUSION: To our knowledge, this is the first study of Ru-SATED scores using IRT and classic test theory analyses. Ru-SATED 4.0 is a psychometrically-valid self-report scale to measure multidimensional sleep health.