Purpose
Evidence for comparative and cost-effectiveness of weight-loss interventions is lacking as there are no obesity-specific measures fit for this purpose. This study aimed to estimate the extent to which a prototype of a brief, multi-dimensional obesity-specific Preference-Based Index of Weight-Related Quality of Life (PBI-WRQL) could fill this gap.
Methods
Longitudinal data from a Canadian bariatric cohort was used. Forty-eight items from the IWQoL-Lite, EQ-5D-3L, and SF-12V2 were mapped onto the WHO ICF domains, and one item was chosen for the dimension based on fit to the Rasch model. Individuals’ health ratings (0–100) were regressed on each dimension, and the regression coefficients for the response options were used as weights to generate a total score. Generalized estimation equations were used to compare measure parameters across groups and levels of converging constructs.
Results
Pre-surgery data were available on 201 people (Women: 82%; BMI: 48.8 ± 6.7 kg/m2; age: 43 ± 9.0 years) and on 125 (62%) at 6 months post-bariatric surgery. Seven dimensions with three response options formed the PB-WRQL prototype: Mobility/Physical Function, Pain, Depression, Participation, Energy, Peripheral Edema, and Dyspnea. The prototype showed substantial change (mean + 40) with bariatric surgery, higher than the EQ-5D (mean + 11.5). The prototype showed the strongest relationship with BMI at baseline (t = − 3.68) and was the most sensitive to change in BMI (t = − 3.42).
Conclusion
This study demonstrates that a brief, 7-dimension index weighted by health impact performed as well as the 31-item IWQoL-Lite and better than the EQ-5D-3L. These findings demonstrate the potential value of the brief PB-WRQL prototype index and support its further development using preference weights to reflect the current generation’s needs and concerns.