Aim: This study aimed to develop a Japanese version of the Caregiving Interface Work Scale (J-CIWS) for use with employed Japanese family caregivers. Methods: Permission was obtained from the developer of the original CIWS. The CIWS contains 20 items: 10 measuring care interface work (CIW) and 10 measuring work interface care (WIC). Responses are measured on a five-point Likert scale. The J-CIWS was developed through forward- and back-translation and cognitive interviews of employed family caregivers. An internet survey was conducted with 116 employed family caregivers, and 78 participants answered a retest. Questionnaire items included the J-CIWS and demographic factors. Factor analysis was conducted to determine the J-CIWS factor structure. Validity was assessed based on known-groups, convergent and discriminant validity. Internal consistency was examined by calculating Cronbach's α. Test–retest reliability was examined by calculating the Pearson's correlation coefficient. Results: The mean participant age was 50.3 years; 74 (63.8%) were male. The average weekly working and caregiving hours were 41.6 and 12.1 h, respectively. Confirmatory factor analysis supported the original two-factor model. High internal consistency (Cronbach's alpha >0.90) and sufficient test–retest reliability (weighted κ score >0.45) were demonstrated for both subscales. Convergent and discriminant validity were acceptable for the two subscales (CIW and WIC). Conclusions: This study confirmed the usefulness of the CIWS within a Japanese context. The J-CIWS may be useful for evaluating the extent of the conflict between work and care among employed family caregivers. Geriatr Gerontol Int 2021; 21: 254–261.
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