Psychometric evaluation of the impact of weight on quality of life-lite questionnaire (IWQOL-lite) in a community sample

Abstract

The short form of impact of weight on quality of life (IWQOL)-Lite is a 31-item, self-report, obesity-specific measure of health-related quality of life (HRQOL) that consists of a total score and scores on each of five scales--physical function, self-esteem, sexual life, public distress, and work--and that exhibits strong psychometric properties. This study was undertaken in order to assess test-retest reliability and discriminant validity in a heterogeneous sample of individuals not in treatment. Individuals were recruited from the community to complete questionnaires that included the IWQOL-Lite, SF-36, Rosenberg self-esteem (RSE) scale, Marlowe-Crowne social desirability scale, global ratings of quality of life, and sexual functioning and public distress ratings. Persons currently enrolled in weight loss programs or with a body mass index (BMI) of less than 18.5 were dropped from the analyses, leaving 341 females and 153 males for analysis, with an average BMI of 27.4. For test-retest reliability, 112 participants completed the IWQOL-Lite again. ANOVA revealed significant main effects for BMI for all IWQOL-Lite scales and total score. Females showed greater impairment than males on all scales except public distress. Internal consistency ranged from 0.816 to 0.944 for IWQOL-Lite scales and was 0.958 for total score. Test-retest reliability ranged from 0.814 to 0.877 for scales and was 0.937 for total score. Internal consistency and test-retest results for overweight/obese subjects were similar to those obtained for the total sample. There was strong evidence for convergent and discriminant validity of the IWQOL-Lite in overweight/obese subjects. As in previous studies conducted on treatment-seeking obese persons, the IWQOL-Lite appears to be a reliable and valid measure of obesity-specific quality of life in overweight/obese persons not seeking treatment.