Performance of a weight-related measure of quality of life in a psychiatric sample

The Impact of Weight on Quality of Life-Lite (IWQOL-Lite) questionnaire has been validated previously in weight loss program participants and community volunteers. Because of the prevalence of obesity in individuals with schizophrenia and bipolar disorder, this study evaluates the psychometric performance of the IWQOL-Lite in these populations. A sample of 111 individuals with schizophrenia (mean age = 43.5; mean BMI = 32.6; 42.3% female; 59.5% Caucasian) and 100 with bipolar disorder (mean age = 42.8; mean BMI = 34.8; 66.0% female; 81.0% Caucasian) were recruited from four programs. Height and weight measurements were taken and participants completed the IWQOL-Lite, Medical Outcomes Study Short-Form-36 (SF-36), and Global Ratings of quality of life. Sixty-five participants completed the IWQOL-Lite 1-2 weeks later to determine stability of results. Sixty-four percent of schizophrenic participants and 68.0% of bipolar participants were obese. The IWQOL-Lite demonstrated excellent reliability in the current sample, with alpha coefficients ranging from 0.874 to 0.970 and test-retest coefficients ranging from 0.740 to 0.945. Correlations with collateral measures and BMI supported the construct validity of the IWQOL-Lite in this population. The IWQOL-Lite is a reliable and valid measure for assessing weight-related quality of life in individuals with schizophrenia and bipolar disorder.