title: Factors Predictive of Weight Gain and Implications for Modeling in Type 2 Diabetes Patients Initiating Metformin and Sulfonylurea Combination Therapy.
abstract: BACKGROUND
  The objectives of this study were to (a) assess the factors associated with weight gain in a population of type 2 diabetes patients escalating from metformin (M) to M+ sulfonylurea (M + S) and (b) evaluate whether healthcare resource utilization associated with being overweight or obese is underestimated in typical health economic evaluations.
  
  
  METHODS
  The study was a retrospective cohort study using UK Clinical Practice Research Datalink linked to Hospital Episode Statistics (CPRD/HES) data. The association between baseline phenotypic factors and weight gain was assessed using logistic regression. Hospitalization incidence rates per 1000 person-years for major diabetes-related complications according to body mass index (BMI) at baseline were estimated from the data (observed) and compared to those obtained from a validated diabetes model (predicted).
  
  
  RESULTS
  11,071 patients were included in the analysis; approximately 40% gained weight in the first year following escalation to M + S. Baseline age, HbA1c and gender were found to be predictors of weight gain [odds ratios 0.99 (1-year increment), 1.11 (1% increment) and 0.81 (female vs male), respectively, p < 0.001]. Observed vs predicted incidence rates of hospitalization were 265 vs 13 (normal), 297 vs 31 (overweight), 223 vs 50 (obese) and 378 vs 41 (severe obese).
  
  
  CONCLUSIONS
  This analysis suggests there are identifiable patient characteristics predictive of weight gain that may be informative to clinical and economic decision making in the context of patients escalating from M to an M + S regimen. Hospital admissions in people with type 2 diabetes were generally under-predicted. A particular focus of future research should be the need for diabetes models to make the likelihood of experiencing an event conditional on BMI.
  
  
  BACKGROUND
  Takeda Development Centre Europe Ltd., UK.
authors.affiliation: Health Economics and Outcomes Research Ltd, Cardiff, UK. jason.gordon@heor.co.uk.|Public Health, University of Adelaide, Adelaide, Australia. jason.gordon@heor.co.uk.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Gordon
authors.affiliation: Llandough Hospital, Diabetes Resource Centre, Cardiff, UK.
authors.forename: Marc
authors.initials: M
authors.lastname: Evans
authors.affiliation: Global Outcomes Research, Takeda Development Centre Europe, TDC (Europe) Ltd, London, UK.
authors.forename: Jorge
authors.initials: J
authors.lastname: Puelles
authors.affiliation: Health Economics and Outcomes Research Ltd, Cardiff, UK.|Centre for Health Economics, Swansea University, Swansea, UK.
authors.forename: Philip C
authors.initials: PC
authors.lastname: McEwan
keywords: Diabetes modeling; Therapy escalation; Type 2 diabetes; Weight gain