Translation and Validation Testing of the Constipation-Related Quality of Life Scale for Use in Japan

Introduction Establishing a scale that can easily be used to appropriately measure the impact of constipation on the quality of life in Japan is a first step toward addressing this important health issue. We developed a Japanese language version of the Constipation-Related Quality of Life scale, which has 18 items and four subscales, and then subjected it to validation testing. Methods After translation according to a standardized and commonly used procedure, the Japanese version of the Constipation-Related Quality of Life scale was administered to people in an internet-based panel, in March 2023. The participants included 1,276 adults who had constipation (median age: 60 years, 690 {54.1%} males). The outcome measures included the Constipation-Related Quality of Life scale, the Constipation Scoring System (an index of constipation severity), and the Medical Outcomes Study (MOS) eight-item short form (a measure of generic health-related quality of life). Results Confirmatory factor analysis (four-factor model) indicated that all 18 Constipation-Related Quality of Life items had sufficiently high factor loadings (0.686-0.926). Internal consistency reliability was high (Cronbach's alpha: 0.86-0.94). Scores on the social impairment subscale and on the distress subscale of the Constipation-Related Quality of Life scale were significantly worse in the participants who had worse scores on the social functioning and mental health domains, respectively, of the MOS eight-item short form, which indicates good concurrent validity. Regarding criterion-based validity, the four subscale scores differed significantly among the four constipation-severity groups. The four subscale scores were also 1.16-4.53 times more sensitive than the MOS eight-item short form's mental component score to differences among the four constipation-severity groups (relative validity: 1.16-4.53), which indicates good discriminant validity. Conclusion The Japanese version of the Constipation-Related Quality of Life scale can be used with confidence in its factor structure, its concurrent, criterion-based, and discriminant validity, and its internal consistency reliability.