Background Identifying the modifiable risk factors for childhood mortality using population-attributable fractions (PAFs) estimates can inform public health planning and resource allocation in low- and middle-income countries (LMICs). We estimated PAFs for key population-level modifiable risk factors of neonatal, infant, and under-five mortality in LMICs.

Methods We used the most recent Demographic and Health Survey data sets (2010–22) from 48 LMICs, encompassing 35 sub-Saharan African countries and 13 countries from South and Southeast Asia (n = 506 989). We used generalised linear latent mixed models to compute odds ratios (ORs), and we calculated the PAFs adjusted for commonality using ORs and prevalence estimates for key modifiable risk factors.

Results The highest PAFs of neonatal mortality were attributed to delayed initiation of breastfeeding (>1 hour of birth) (PAF = 23.9; 95% confidence interval (CI) = 23.1, 24.8), uncleaned cooking fuel (PAF = 6.2; 95% CI = 6.4, 7.8), infrequent antenatal care (ANC) visits (PAF = 4.3; 95% CI = 3.3, 5.9), maternal lack of formal education (PAF = 3.9; 95% CI = 2.7, 5.3), and mother’s lacking two doses of tetanus injections (PAF = 3.0; 95% CI = 1.9, 3.9). These five modifiable risk factors contributed to 41.4% (95% CI = 35.6, 47.0) of neonatal deaths in the 48 LMICs. Similarly, a combination of these five risk factors contributed to 40.5% of infant deaths. Further, delayed initiation of breastfeeding (PAF = 15.8; 95% CI = 15.2, 16.2), unclean cooking fuel (PAF = 9.6; 95% CI = 8.4, 10.7), mothers lacking formal education (PAF = 7.9; 95% CI = 7.0, 8.9), infrequent ANC visits (PAF = 4.0; 95% CI = 3.3, 4.7), and poor toilet facilities (PAF = 3.4; 95% CI = 2.6, 4.3) were attributed to 40.8% (95% CI = 36.4, 45.2) of under-five deaths.

Conclusions Given the current global economic climate, policymakers should prioritise these modifiable risk factors. Key recommendations include ensuring that women enter pregnancy in optimal health, prioritising the presence of skilled newborn attendants for timely and proper breastfeeding initiation, and enhancing home-based care during the postnatal period and beyond.