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 ± 11.6 years, range 19-65 years). The distribution and reliability of the scale scores were examined in terms of Cronbach's alpha coefficient. 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 ± 2.72 points, and range of 0-12. The internal reliability of the scale was α = 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.