Heterogeneous wealth-related differences in modern contraceptive use in Bangladesh: a machine learning-based...

Conventional logistic regression estimates a single population-average odds ratio (OR), masking heterogeneity in how social determinants affect health outcomes across population subgroups. We applied machine learning (ML)-based stratified g-computation to estimate individual-specific wealth-associated counterfactual ORs of household wealth on modern contraceptive use among currently married Bangladeshi women in the two extreme wealth quintiles.

We analyzed 11,510 currently married women in the poorest and richest wealth quintiles from the Bangladesh Demographic and Health Survey (BDHS) 2022. Six model classes (Logistic Regression, Random Forest, Gradient Boosting, XGBoost, LightGBM, Stacking Ensemble) were compared with five-fold cross-validated area under the receiver operating characteristic curve (AUC). SHapley Additive exPlanations (SHAP) analysis, primary sampling unit (PSU)-level bootstrap confidence intervals (CIs), doubly-robust augmented inverse probability weighted (AIPW) sensitivity analysis, Benjamini-Hochberg false discovery rate (BH-FDR) correction, and E-value analysis were conducted. Findings apply to the two extreme wealth quintiles and should not be extrapolated to the middle three quintiles.

Modern contraceptive prevalence was 37.7% in the poorest quintile versus 32.6% in the richest. The Stacking Ensemble achieved the highest CV-AUC (0.7108). All six AIPW estimates were near-null ([Formula: see text]-0.83), revealing that the aggregate wealth effect is zero because opposing subgroup effects cancel: a [Formula: see text] percentage-point absolute risk difference (ARD) in the 35-49/higher-education subgroup is precisely offset by a [Formula: see text] percentage-point ARD in the 15-24/primary-education subgroup. Individual ORs exhibited a Gini coefficient of 0.4525 (95% bootstrap CI: 0.4475-0.4568); interaction tests confirmed heterogeneity by education ([Formula: see text]) and age ([Formula: see text]). Median ORs ranged 6.4-fold: from 0.552 (15-24/primary; FDR [Formula: see text]) to 3.557 (35-49/higher; E-value = 6.57). Parity was the strongest SHAP predictive contributor, followed by employment and age.

Wealth-associated counterfactual OR differences in contraceptive use are patterned within demographic subgroups; population-average estimates are zero because opposing effects cancel, and only individual-level ML-based g-computation reveals this structure. The programmatic targeting framework derived from this approach offers a reproducible prioritisation tool for health equity analyses in any DHS-based survey.