Assessing the psychometric properties of the ICECAP-A capability well-being instrument in the Japanese working population

The ICEpop CAPability measure for Adults (ICECAP-A) was developed to assess quality of life in terms of general well-being. This study aims to evaluate the psychometric properties of the Japanese version of ICECAP-A in the working population. A nationally representative sample of the Japanese working population was collected ( n = 9,243). The psychometric properties of the ICECAP-A were examined in relation to the five-level Euro Quality of Life Five-Dimension Questionnaire (EQ-5D-5L), self-reported diseases, self-perceived symptoms, mental health (Kessler Psychological Distress Scale), and subjective well-being (life satisfaction). The Japanese version of the ICECAP-A demonstrated good internal consistency, with an overall Cronbach’s alpha coefficient of 0.84. The mean scores for ICECAP-A (Japan), ICECAP-A (UK), and EQ-5D-5L (Japan) were 0.74, 0.65, and 0.89, respectively. The ICECAP-A score was moderately correlated with the EQ-5D-5L score, the anxiety and depression dimension of EQ-5D-5L, EQ-VAS, and mental health, and strongly correlated with life satisfaction. Exploratory factor analysis indicated that ICECAP-A and EQ-5D-5L capture largely distinct aspects of quality of life, with ICECAP-A serving as a complement to EQ-5D-5L. The EQ-5D-5L performed better in assessing self-reported diseases and self-perceived symptoms, whereas ICECAP-A outperformed EQ-5D-5L in assessing life satisfaction and various job-related factors. The Japanese version of ICECAP-A is a valid instrument for assessing capability well-being in the working population. Application of ICECAP-A in economic evaluations of public health policies and interventions may capture broader aspects of quality of life.