The association of body mass index and health-related quality of life: Data from two weight-loss interventional studies

Abstract Purpose The correlation between body mass index (BMI) and utility in patients with overweight or obesity was assessed using health-related quality of life (HRQoL) data collected in two weight-loss interventional studies, SCALE and STEP 1. Methods Short-Form Health Survey 36-Item (SF-36) scores from SCALE and STEP 1 were mapped to EuroQoL-5 dimensions-3 levels (EQ-5D-3L) using an established algorithm to derive utilities for the UK. SF-36 scores from STEP 1 were converted into Short-Form six-dimensions (SF-6D) utilities for Portugal, using the tool developed by the University of Sheffield. Correlations between utility scores and BMI at baseline were assessed by multiple linear regression analyses, controlling for demographic and clinical parameters. Results Higher baseline BMI was correlated with lower EQ-5D-3L/SF-6D utilities in all analyses, although the correlation was nonsignificant. Assuming linearity between BMI ranges 30–40 kg/m2, a unit increase predicted a utility loss of − 0.0041 and − 0.0031 on EQ-5D-3L for males and females, respectively, in SCALE, − 0.0039 and − 0.0047 in STEP 1, and − 0.0027 and − 0.002 on SF-6D males and females, respectively. Presence of hypertension and older age were significantly negatively correlated with SCALE EQ-5D-3L. Age, presence of coronary artery diseases (CADs) and previous smoking were significantly negatively correlated with STEP 1 EQ-5D-3L. Only presence of CADs was significantly negatively correlated with STEP 1 SF-6D. Males had significantly higher utilities compared with females in the UK analyses. Conclusion These findings are useful to inform cost-effectiveness analyses in obesity whereby multiple factors, along with BMI, are used to calculate quality-adjusted life-years.