Effect of insecticide treated nets or indoor residual spraying on Malaria or Anemia risk among children aged 6-59 months in Uganda : a propensity score matched analysis

Abstract

Background: Malaria and anemia represent critical health challenges for Ugandan children under five, with national prevalence rates of 53% for anemia and persistently high malaria incidence. While Insecticide-Treated Nets (ITNs/LLINs) and Indoor Residual Spraying (IRS) serve as primary vector control interventions, evidence regarding their comparative effectiveness in real-world settings remains limited due to methodological constraints in observational studies. This study addresses this gap by employing Propensity Score Matching methods to evaluate the causal effects of these interventions on both malaria and anemia outcomes while controlling for confounding factors. Methods: A Propensity Score Matching (PSM) analysis was conducted using nationally representative data from the Uganda Malaria Indicator Survey (UMIS) 2018-2019 involving 5,549 children aged 6-59 months. The Average Treatment Effect on the Treated (ATT) was estimated for ITNs/LLINs and IRS adjusting for key sociodemographic and geographic confounders such as maternal education, household wealth and region. Rosenbaum bounds sensitivity analysis assessed robustness to unobserved bias. Results: Malaria and anemia prevalence among children aged 6-59 months was 19.6% and 45% respectively. ITNs/LLINs use was associated with 5.5% reduction in malaria risk (ATT=-0.055; 95% CI: -0.107 to -0.002) and a 15.4% reduction in anemia risk (ATT= -0.154; 95% CI: -0.221 to -0.087). IRS use was associated with 14% reduction in malaria risk (ATT= -0.140; 95% CI: -0.208 to -0.072) and a 11.6% reduction in anemia risk (ATT= -0.116; 95% CI: -0.186 to -0.046). Rosenbaum bounds Sensitivity analyses indicated the effect of IRS on malaria was highly robust to hidden bias, while the effect of ITNs/LLINs on malaria was more sensitive. Conclusion: Both ITNs/LLINs and IRS significantly reduce the risk of malaria and anemia, but with differential efficacy. IRS demonstrates superior protection against malaria, making it a strategic tool for targeted deployment in high-transmission areas. Conversely, ITNs/LLINs showed a stronger effect on reducing anemia and should be maintained as a universal intervention. These findings advocate for an integrated, data-driven malaria control strategy that leverages the complementary strengths of both interventions to mitigate Uganda's dual disease burden effectively.