Designing and Psychometric Evaluation of Morbid Obesity Quality of life Questionnaire: A Mixed Methods Study

Abstract

Background: Morbid obesity negatively affects all aspects of quality of life (QOL); therefore, the assessment of QOL can be a useful criterion to evaluate obesity outcome. Objective: The present study aimed to design a QOL questionnaire in morbid obesity and assess its validation features. Methods: This sequential-exploratory mixed-methods study was conducted in both qualitative and quantitative stages. The qualitative stage was carried out through 20 semi-structured interviews with morbidly obese people. Furthermore, the initial items of the questionnaire were obtained by a review of related literature. In the next stage, face, content, and construct validity were assessed. The construct validity was examined by exploratory factor analysis with 319 people. Moreover, Cronbach’s alpha and test-retest correlation coefficient were calculated to evaluate the reliability of the questionnaire. Furthermore, confirmatory factor analysis was assessed. Results: Based on the results of the quantitative stage, an 80-item pool was extracted. The exploratory factor analysis yielded six factors that explained 50.62% of the variance. The factors of one to six were as follows: self-dissatisfaction (15 items), functional disorders (7 items), spiro-mental experiences (11 items), perso-social isolation (7 items), physical changes (7 items), and financial pressure (3 items). The final Cronbach’s alpha coefficient of the 50-item questionnaire was calculated at 0.94. Moreover, the intra-class correlation coefficient between the test and retest scores was estimated at 0.97. All indicators of confirmatory factor analysis demonstrated that goodness of fit was acceptable for each factor. Furthermore, this questionnaire had appropriate interpretability, feasibility, and did not have any floor and ceiling effects. Conclusion: This valid and reliable questionnaire can be used as a suitable measurement tool for assessing the QOL of morbidly obese people in Iran and other countries with similar cultural features. This questionnaire can improve the quality of future clinical research on obesity. In addition, health care providers can perform a peculiar role in the provision of efficient services to patients to prevent obesity and its associated complications.