Long-Term Trends and Age-Specific Dynamics of Under-Five Mortality in Cameroon (1991–2022): Evidence from Six Consecutive DHS and MIS Waves

Under-five mortality (U5M) remains a critical public health challenge in sub-Saharan Africa, and Cameroon illustrates this complexity.This study analyzes six consecutive DHS and MIS surveys (1991, 1998, 2004, 2011, 2018, 2022), covering 39,763 live births and 3,132 under-five deaths across 31 years, to document national U5MR trends, age-specific dynamics, urban-rural differentials, and regional heterogeneity under complex survey design.Survey-weighted estimates with 95% confidence intervals revealed a 62.4% reduction in the national U5MR, from 85.7 per 1,000 live births (1991) to 32.2 per 1,000 (2022), following a non-monotonic trajectory with a statistically significant anomalous peak in 2004 (102.0%).Neonatal mortality remained essentially flat across 1991-2018 (28-32‰), constituting a 'neonatal squeeze' whereby the neonatal share of U5M rose from 37% (1991) to an estimated 87% (2022).The rural-to-urban mortality ratio peaked at 1.46 in 2011 before converging to 1.18 by 2022.Persistent regional heterogeneity was documented across all waves, with northern regions (Far North, North, Adamaoua, North-West) recording U5MR two to three times above the national average, while the West region consistently showed the most protective profile.These findings show that while absolute progress has been substantial, child survival gains in Cameroon remain profoundly uneven: the neonatal period now concentrates the remaining burden while northern regions continue to lag.Meeting SDG 3.2 targets by 2030 requires an urgent reorientation of child survival strategies toward facility-based neonatal care, universal skilled birth attendance, and geographically targeted investments in the four priority northern regions.