title: Does Higher Spending Improve Survival Outcomes for Myocardial Infarction? Examining the Cost-Outcomes Relationship Using Time-Varying Covariates.
abstract: OBJECTIVE
  Previous patient-level acute myocardial infarction (AMI) research has found higher hospital spending to be associated with improved survival; however, survivor-treatment selection bias traditionally has been overlooked. The purpose of this study was to examine the AMI cost-outcome relationship, taking into account this form of bias.
  
  
  METHODS
  Hospital Discharge Abstract data tracked costs for AMI hospitalizations. Ontario Vital Statistics data tracked patient mortality.
  
  
  METHODS
  A standard Cox survival model was compared to an extended Cox model using hospital costs as a time-varying covariate to examine the impact of cost on 1-year survival in a cohort of 30,939 first-time AMI patients in Ontario, Canada, from 2007 to 2010.
  
  
  RESULTS
  Higher patient-level AMI spending decreased the hazard of dying (Standard Model: log-cost hazard ratio: 0.513, 95 percent CI: 0.479-0.549; Extended Model: log-cost hazard ratio: 0.700, 95 percent CI: 0.645-0.758); however, the protective effect was overestimated by 62 percent when survivor-treatment bias was overlooked. In the extended model, a 10 percent increase in spending was associated with a 3.6 percent decrease in hazard of death.
  
  
  CONCLUSIONS
  The findings of this study suggest that if survivor-treatment bias is overlooked, future research may materially overstate the protective effect of patient-level spending on outcomes.
authors: Department of Population Health, University of Ottawa, Institute for Clinical Evaluative Sciences, 35 Soho Crescent, Ottawa, ON, Canada, K1N6N5.
authors: Deborah
authors: D
authors: Cohen
authors: Ottawa Hospital Research Institute, University of Ottawa, Institute for Clinical Evaluative Sciences, Ottawa, ON, Canada.
authors: Douglas G
authors: DG
authors: Manuel
authors: Centre for Global Health, Institute of Population Health, Ottawa Health Research Institute, University of Ottawa, Ottawa, ON, Canada.
authors: Peter
authors: P
authors: Tugwell
authors: Health Analysis Division, Statistics Canada, Ottawa, ON, Canada.
authors: Claudia
authors: C
authors: Sanmartin
authors: Ottawa Hospital Research Institute, Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, ON, Canada.
authors: Tim
authors: T
authors: Ramsay
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003365:Costs and Cost Analysis; D004469:Economics, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006750:Hospital Distribution Systems; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality*; D009864:Ontario; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D010359:Patient Readmission / Q000706:statistics & numerical data; D016016:Proportional Hazards Models; D012959:Socioeconomic Factors; D013997:Time Factors
keywords: Myocardial infarction; cost-outcome relationships; survivor-treatment selection bias; time-varying covariates