The impact on utilities of differences in body weight among Canadian patients with type 2 diabetes

The objective of this study was to estimate utility values for hypothetical health states that describe differences in weight and quality of life associated with type 2 diabetes mellitus (DM) from Canadians with type 2 DM. The impact on utility values was examined separately for participants with a body mass index (BMI) of 18 to less than 25 kg/m(2) ('healthy'), 25 to less than 30 ('overweight'), and 30 or more ('obese').

The health state descriptions were modified from a published diabetes utility study. Health states included a base-case type 2 DM health state (at participants' current weight), and six health states where the weight and attendant quality of life impact varied (base case ±3%, ±5%, and ±7% weight). Utilities were elicited using the time trade-off technique. Linear regression modeling was used to estimate the utility increment or decrement associated with a one unit difference in BMI.

Among 96 participants, the mean age was 55 years and 51% were men. The mean BMI was 32 kg/m(2) and 84% wanted to lose weight. The mean (SD) utility for the base-case state was 0.911 (0.013). Mean utilities (utility decrements) were 0.907 (-0.004), 0.865 (-0.046) and 0.806 (-0.105) for the health states describing an increased weight of 3%, 5% and 7%, respectively; and 0.923 (+0.012), 0.940 (+0.029) and 0.949 (+0.038) for the health states describing a decreased weight of 3%, 5% and 7%, respectively. For every increase of 1 kg/m(2) BMI there was an associated decrease in utility of 0.0472 (95% CI: 0.0375, 0.0569) and for every decrease of 1 kg/m(2) BMI there was an associated increase in utility of 0.0171 (95% CI: 0.0103, 0.0238).

The preferences of Canadian patients with type 2 DM for diabetes-related health states varied according to the weight, and quality of life impact, associated with that health state. Increased weight had a greater effect on utilities than decreased weight.