The validity and reliability of the Japanese version of RU-SATED

Objective: We developed a Japanese version of RU-SATED (RU-SATED-J), a simple self-rated scale for measurement of multidimensional sleep health, and examined its reliability and psychometric validity.Method: The RU-SATED-J was developed by a rigorous reverse translation process. It consists of six questions, each with three Likert-type response options. The total score (range 0-12) was calculated by summing the item scores. Psychometric characteristics were tested in an observational cross-sectional study involving factory workers in Japan (n = 177, mean age 42.8 & PLUSMN; 11.6 years, range 19-65 years). The distribution and reliability of the scale scores were examined in terms of Cronbach's alpha coeffi-cient. The convergent and divergent validity of the scale score were assessed by examining the correlations of various factors with the Insomnia Severity Index (ISI) and the Epworth Sleepiness Scale (ESS).Results: The distribution of scores was left-skewed, with a mean of 8.21 & PLUSMN; 2.72 points, and range of 0-12. The internal reliability of the scale was a = 0.758. The total score showed a significant negative correlation with the ISS (rs =-0.542, P < 0.001) and the ESS (rs =-0.178, P = 0.018). Exploratory factor analysis (EFA) demonstrated a two-factor structure. Confirmatory factor analysis (CFA) showed that the goodness of fit of the higher-order factor model had a Root Mean Square Error of Approximation (RMSEA) of < 0.001 and a Comparative Fit Index (CFI) of 1.00, confirming its factorial validity.Conclusion: The RU-SATED is a promising new instrument for measuring multi-dimensional sleep health perception among Japanese adults. Further general population studies using this Japanese version of the questionnaire should be considered.