The Emerging Dominance of Genetic Disorders in Under 5 Mortality: A Global Comparative Assessment and Frontier Analysis, 1990 to 2021

BackgroundGlobal under-5 mortality has declined by approximately 60% since 1990, driven largely by reductions in communicable, maternal, neonatal, and nutritional (CMNN) diseases. Yet the degree to which genetic disorders now impede further progress toward Sustainable Development Goal (SDG) 3.2 remains poorly quantified. No prior study has assessed the aggregate burden of genetically determined conditions as a unified category across the full spectrum of countries and development levels. MethodsUsing data from the Global Burden of Disease (GBD) Study 2021, we defined a composite "Total Genetic Burden" by aggregating 16 genetically determined causes of death, encompassing congenital birth defects, hemoglobinopathies, cystic fibrosis proxies, and spinal muscular atrophy proxies, across 204 countries and territories from 1990 to 2021. Age-standardized mortality rates (ASMR), proportional mortality ratios (PMR), years of life lost (YLLs), and 95% uncertainty intervals (UIs) were calculated. Temporal trends were assessed to evaluate the shifting burden over the study period. Age-specific mortality density was computed to identify periods of peak vulnerability. Deterministic frontier analysis (log-transformed quadratic quantile regression at the 5th percentile) was applied to quantify potentially avoidable mortality relative to best-observed global performance at each level of socioeconomic development. ResultsThe age-standardized mortality rate of genetic disorders in children under 5 declined from 1990 to 2021; however, the proportional mortality ratio nearly doubled (from 5.76% to 10.76%), and genetic disorders rose from the fifth to the third leading cause of under-5 death. This shift was most pronounced in high Socio-demographic Index (SDI) countries, where genetic disorders accounted for over 40% of all under-5 deaths in some nations (e.g., Libya, 46.32%). An "Epidemiological Paradox" emerged: absolute mortality correlated negatively with SDI (R = -0.79, P < 0.001), whereas proportional mortality correlated positively (R = 0.80, P < 0.001). Age-specific analysis revealed a "Neonatal Stronghold," with genetic disorders accounting for 57% of combined genetic-versus-infectious deaths in the first week of life but only 8% in children aged 1-4 years. Frontier analysis identified substantial efficiency gaps across all SDI quintiles; China and Japan sat on the effective frontier, while Afghanistan, Nigeria, and even the United States exhibited considerable potentially avoidable mortality. ConclusionsGenetic disorders have shifted from a secondary concern to a leading structural barrier to further reductions in child mortality. Achieving SDG 3.2 will require broadening global child health priorities beyond infection control to include prenatal screening, newborn screening programs, and pediatric surgical capacity building, particularly in low- and middle-income countries.