Reducing demographic inequality in emergency medical service: two bi-objective spatial optimization approaches

Abstract Background Population demographic structures have become increasingly complex worldwide, posing new challenges for planning Emergency Medical Services (EMS) in ways to improve equality. Existing geographical studies have mainly focused on EMS equality in geographic accessibility or coverage, while demographic equality has received less attention. This study develops spatial optimization models that incorporate demographic equality into facility location planning. Methods Two bi-objective spatial optimization models are developed to improve demographic equality, while maintaining efficiency provision of EMS. In detail, the two models have the same efficiency objective that is to maximize the service coverage ( Z 1 ). Then, the first model (M1) addresses coverage-based demographic equality by minimizing disparities in coverage rates among population groups ( Z 2 ). The second model (M2) focused on accessibility-based demographic equality by minimizing the maximum average travel time among demographic groups ( Z 3 ). The models were applied to Wuhan, China, using age groups as the demographic representation and historical emergency medical service records to estimate spatially varying age-specific risks. Results The empirical results showed that both models were effective in improving demographic equality, although clear trade-offs were observed between equality enhancement and service efficiency. For M1, the nine Pareto-optimal solutions indicated that coverage-based demographic inequality, measured by Z 2 , decreased from 7.64% to 0.61%. This improvement in demographic equality, however, required an efficiency loss of up to 3.94% of total coverage. For M2, improving accessibility for the worst-served demographic group by 1.4 min ( Z 3 ) required a remarkable trade-off. The equality-oriented solution requires a 3.98% of efficiency loss compared with the efficiency-oriented solution. Both models consistently identified southern Hongshan and northern Jiangxia as priority areas for new EMS stations. Conclusions The proposed framework provides a transferable approach for integrating population-group equality into healthcare planning and supports more equitable allocation of EMS resources.