Chinese version of Impact of Weight on Quality of Life for Kids: psychometric properties in a large school-based sample

The Impact of Weight on Quality of Life for Kids (IWQOL-Kids) is the first self-report questionnaire for assessing weight-related quality of life for youth. However, there is no Chinese version of IWQOL-Kids. Thus, the objective of this research was to translate IWQOL-Kids into Mandarin and evaluate its psychometric properties in a large school-based sample.The total sample included 2282 participants aged 11-18 years old, including 1703 non-overweight, 386 overweight and 193 obese students. IWQOL-Kids was translated and culturally adapted by following the international guidelines for instrument linguistic validation procedures. The psychometric evaluation included internal consistency, test-retest reliability, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), convergent validity and discriminant validity.Cronbach's α for the Chinese version of IWQOL-Kids (IWQOL-Kids-C) was 0.956 and ranged from 0.891 to 0.927 for subscales. IWQOL-Kids-C showed a test-retest coefficient of 0.937 after 2 weeks and ranged from 0.847 to 0.903 for subscales. The original four-factor model was reproduced by EFA after seven iterations, accounting for 69.28% of the total variance. CFA demonstrated that the four-factor model had good fit indices with comparative fit index = 0.92, normed fit index = 0.91, goodness of fit index = 0.86, root mean square error of approximation = 0.07 and root mean square residual = 0.03. Convergent validity and discriminant validity were demonstrated with higher correlations between similar constructs and lower correlations between dissimilar constructs of IWQOL-Kids-C and PedsQL™ 4.0. The significant differences were found across the body mass index groups, and IWQOL-Kids-C had higher effect sizes than PedsQL™4.0 when comparing non-overweight and obese groups, supporting the sensitivity of IWQOL-Kids-C.IWQOL-Kids-C is a satisfactory, valid and reliable instrument to assess weight-related quality of life for Chinese children and adolescents aged 11-18 years old.