Volume 50 | Number 5 | October 2015

Abstract List

Deborah Cohen Ph.D., Douglas G. Manuel M.D., F.R.C.P.C., M.Sc., Peter Tugwell M.D., F.R.C.P.C., M.Sc., Claudia Sanmartin Ph.D., Tim Ramsay Ph.D.


Previous patient‐level acute myocardial infarction () 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 cost‐outcome relationship, taking into account this form of bias.

Data Sources

Hospital Discharge Abstract data tracked costs for hospitalizations. Ontario Vital Statistics data tracked patient mortality.

Study Design

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 patients in Ontario, Canada, from 2007 to 2010.

Principal Findings

Higher patient‐level spending decreased the hazard of dying (Standard Model: log‐cost hazard ratio: 0.513, 95 percent : 0.479–0.549; Extended Model: log‐cost hazard ratio: 0.700, 95 percent : 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.


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.