Socioeconomic and geographic inequalities in insecticide-treated net utilization in Tanzania: evidence from a multilevel and concentration index analysis of TDHS-MIS 2015–2016

Despite large-scale distribution of insecticide-treated nets (ITNs) in Tanzania, disparities in utilization persist. Understanding socioeconomic and geographic inequalities in ITN use is critical for advancing equitable malaria control. This study assesses determinants of ITN utilization and quantifies wealth-related inequality using nationally representative survey data. Data were drawn from the Tanzania Demographic and Health Survey and Malaria Indicator Survey (TDHS-MIS) 2015–2016. A weighted sample of 37,169 households was analyzed. Survey-adjusted multilevel logistic regression was used to account for clustering at enumeration area level. An empty model estimated the intraclass correlation coefficient (ICC), followed by adjusted models including household-level covariates. Socioeconomic inequality in ITN utilization was quantified using the concentration index and concentration curves. An interaction term between poverty and residence was introduced to examine compounded disadvantage. The weighted prevalence of ITN utilization was 55.1% (95% CI: 53.9–56.4). Larger household size (AOR = 1.056; 95% CI: 1.049–1.063), male-headed households (AOR = 1.242; 95% CI: 1.170–1.318), and urban residence (AOR = 1.093; 95% CI: 1.037–1.153) were positively associated with ITN use. Poverty (AOR = 0.915; 95% CI: 0.874–0.957) and increasing age of household head (AOR = 0.993; 95% CI: 0.992–0.995) significantly reduced the likelihood of utilization. The ICC (3.7%) indicated contextual clustering effects. The concentration index was +0.072 (p < 0.001), demonstrating pro-rich inequality. Predicted probabilities revealed the lowest ITN utilization among rural poor households (48.2%) compared with urban non-poor households (61.8%), confirming compounded socioeconomic and geographic disadvantage. Although national ITN coverage exceeds 50%, utilization in Tanzania remains unequally distributed. Pro-rich inequality and rural poverty significantly constrain equitable malaria protection. Malaria control strategies must shift from coverage-focused approaches toward equity-oriented implementation frameworks, including geographically targeted distribution, poverty-sensitive programming, and routine inequality monitoring. Addressing structural disparities is essential for accelerating progress toward Sustainable Development Goal 3 and malaria elimination targets.