The impact of body weight on patient utilities with or without type 2 diabetes: A review of the medical literature

Background: Weight gain is a common side effect of many therapies for type 2 diabetes (T2DM). Selecting utility values for incorporation into cost-utility analyses (CUAs) of T2DM therapies is difficult because of variations in methodologies to elicit utilities and other study limitations. Methods: A review of the medical literature was conducted to identify studies assessing the impact of body weight on patient utility. Results: Eighteen articles presented either: 1) utility values by body-mass index (BMI) or body weight, or 2) the change in utility scores or quality-adjusted life-years based on unit changes in BMI or body weight. Regardless of the study population or methodology used to elicit utility scores, all studies reviewed found that as body weight increased, patient utility decreased. Utility scores obtained using standard gamble were generally higher than those using time trade-off(TTO) or the EQ-5D. Most studies reported utility scores stratified by BMI and used regression analyses to attribute the difference in utility scores to differences in weight while controlling for other factors. Studies generally assumed a constant change in utility occurs with a one unit change in BMI. Recent studies, however, demonstrate the magnitude of changes in utility may vary depending on 1) valuing weight loss versus weight gain; 2) valuing a small or large change in body weight; and 3) baseline BMI. Conclusions: Various utility values associated with body weight using different methodologies have been published. Careful consideration should be given to determine the most appropriate utility values to use in CUAs of T2DM therapies.