68-3

48/130

244and used as the subscale score. The total score of the five subscale scores was taken as the total SEWB score. The process of selecting question-naire items and validation as well as English trans-lation of 21 items was reported previously by some of the authors of the present study6, 8).TranslationFirst, the German version of the SEWB scale was translated into Japanese by one of the authors (YK). Next, a bilingual (German and Japanese) author (FN), who had not read the original items, conducted back-translation into German. The German author of this study (JD) examined the quality of translated versions, having compared them with the original German version. Based on this author’s evaluation, corrections were made for words, meanings, and item content by the authors (KY, YK, and FN) with the assistance of a Japa-nese employee in JD’s laboratory. The final items of the J-SEWB scale are listed in the Appendix. Survey questionnaire and protocolThe questionnaire used in the current study consisted of the J-SEWB scale and questions regarding sociodemographic variables, such as age, gender, job, work conditions, and annual income. The internet survey was outsourced to a research company (hamon Inc, Yokohama, Japan). Of the 1,052,566 registered individuals, 4,057 full-time employees aged 20 to 64 years who worked 30 hours or more a week were randomly selected (2,399 men and 1,658 women). These respondents were asked to answer an online questionnaire from September 8th, 2021, adjusting the number of responses by age group to be similar to the result of Labor Force Survey in Japan (2020)15). The survey was discontinued when the total number of answers reached 600; this sample size was the maximum that the research budget allowed, and exceeded the size (300 or more) that would give stable results in factor analysis16). Other than listed here, there were no conditions to include or exclude study subjects.Statistical analysisThe Cronbach’s α coefficient was calculated for each subscale to assess the internal consistency. Construct validity was examined using principal factor analysis with equamax rotation. Relation-ships among J-SEWB scores and sociodemographic variables were examined using t-test, χ2 test, or analysis of variance. All of the statistical analyses were conducted using IBM SPSS version 26.0.Ethical issueThis study was conducted after approval by the International University of Health and Welfare Research Ethics Committee (21-Ig-13, May 19, 2021). Participants agreed to participate volun-tarily in the survey under a contract with the research company and were anonymous to us; we did not get informed consent from each.Sociodemographic characteristics of 600 partici-pants by gender are shown in Table 1. The propor-tions of participants in each age group were 18.3%, 21.2%, 27.3%, 24.1%, and 9% for the 20–29, 30–39, 40–49, 50–59 and 60–64 years age groups, respec-tively. Participants were mainly office workers (76.2%) and public officials (10.8%) with a smaller proportion of professionals and faculty/researchers (5.7%). Working hours per week were 30–49 hours for most of participants (86.3%), whereas a small proportion (13.7%) reported working 50 hours or more per week. Approximately 30% of participants worked under a non-fixed (flexible) working hours system, whereas the remaining 70% worked under a fixed working hours system. Half of the partici-pants earned 4 million Yen or more per year. Table 2 shows scores and Cronbach’s α coeffi-cients for the J-SEWB scale. Cronbach’s α coeffi-cients were 0.846 to 0.946 for five subscales, and were 0.958 (men), 0.951 (women), and 0.957 (combined) for total SEWB scores. Average scores on the total SEWB and five subscales in men were higher than those in women. These differences were statistically significant (t-test, p < 0.05) except for “Intensification of working hours” and “Use of stimulating substances” (p > 0.05).Table 3 shows factor loadings for 21 items. A scree plot is drawn in the Figure 1. Five factors were extracted by factor analysis, classifying 21 items into their corresponding subscales, except that item 7, “I work more than 10 hours a day without being directed to do so,” which was most heavily loaded on “Prolongation/extension of working Results