Development efficiency and mortality after coronary artery bypass grafting: a national causal inference analysis

Background We evaluated whether development efficiency, the component of the Human Development Index independent of GDP per capita and income inequality, is associated with in-hospital mortality after coronary artery bypass grafting (CABG) in Brazil, and whether this association is mediated by access to elective surgery. Methods We conducted a retrospective ecological panel study using administrative data on CABG hospitalizations within the Brazilian Unified Health System from 2008 to 2024. State-year observations were linked to socioeconomic indicators. Development efficiency was defined as the residual of HDI after regression on GDP per capita and the Gini coefficient. Associations with in-hospital mortality were examined using volume-weighted multilevel models. Absolute causal effects and mediation through urgency status were estimated using g-computation and parametric causal mediation analysis. Results The final analytic panel included 379 state-year observations. A 1–standard deviation increase in development efficiency was associated with a reduction in predicted in-hospital mortality from 6.8% to 5.7% (absolute risk reduction − 1.1% points; p < 0.001). At the population level, this corresponds to approximately one fewer observed death per 91 procedures in states with higher versus lower development efficiency. Mediation analysis indicated that 95.5% of the total effect was attributable to the natural direct effect, while only 4.5% was mediated through urgency status, with no significant indirect effect. Conclusions Development efficiency is an independent and clinically meaningful determinant of survival after CABG in Brazil. Higher income-independent HDI performance is associated with substantial absolute mortality reductions, driven predominantly by direct system-level pathways rather than changes in urgency profile. Strengthening health-system efficiency and perioperative capacity may therefore yield meaningful gains in cardiac surgical outcomes.