A Systems Dynamics Framework for Modelling Under-Five Mortality Reduction Strategies in Northern Nigeria: Integrating Health System, Nutritional, and Socioeconomic Determinants

Under-five mortality in northern Nigeria persists at levels that defy linear programmatic explanation, suggesting the operation of complex, interdependent causal pathways that cross-sectional analyses cannot adequately capture. This study proposes and validates a systems dynamics modelling framework to simulate the effect of integrated child survival interventions on under-five mortality trajectories across Kano, Sokoto, and Zamfara states over a 20-year projection horizon. A causal loop diagram was constructed through participatory group model building with 42 stakeholders including paediatricians, public health specialists, policymakers, and community representatives. Secondary data from NDHS 2018 and 2021, HMIS records, and programme evaluation reports were used to parameterise stock-and-flow equations in the Vensim modelling platform. Scenario simulations tested the independent and combined effects of improving skilled birth attendance, scaling malnutrition treatment coverage, increasing immunisation rates, and expanding maternal education coverage. Single-intervention scenarios produced modest mortality reductions of 12 to 18% over 20 years. Integrated multi-sector scenarios generated synergistic effects, projecting a 47% mortality reduction, significantly exceeding the sum of individual intervention effects. Feedback loops connecting maternal education, nutrition, and healthcare utilisation were identified as key amplifiers of intervention impact. The model revealed time-lagged effects of educational investment with peak impact emerging 8 to 12 years post-investment. This framework provides a novel theoretical contribution to child health systems science in Nigeria, offering a simulation tool for evidence-based priority-setting. Keywords: systems dynamics, under-five mortality, northern Nigeria, modelling, health systems.