Association between regional income inequality and infant mortality rates in Türkiye: an ecological panel analysis of NUTS-2 regions, 2014–2024

Income inequality may affect infant survival through socioeconomic and health-care pathways, but regional evidence from Türkiye remains limited. This study examined the association between regional income inequality and infant mortality rates across the 26 NUTS-2 regions of Türkiye during 2014–2024. This longitudinal ecological panel study used publicly available data from the Turkish Statistical Institute. Income inequality was measured using the Gini coefficient and P80/P20 ratio. Linear mixed-effects models included a regional random intercept and a first-order autoregressive covariance structure for repeated annual observations. Year was modelled categorically in the primary analyses, and between-region and within-region effects were examined separately. Live-birth-weighted sensitivity analyses were used to assess whether differences in the precision of regional IMR estimates affected the findings. The study included 286 region-year observations; income inequality models included 285. From 2014 to 2024, the regional mean Gini coefficient increased from 0.364 to 0.390 and the mean P80/P20 ratio from 6.42 to 7.22, while mean IMR declined from 10.81 to 8.86 per 1,000 live births. After adjustment for categorical year effects, no statistically significant association was detected for either the Gini coefficient (B = 0.041; 95% CI: −0.025 to 0.106; p = 0.221) or the P80/P20 ratio (B = 0.054; 95% CI: −0.145 to 0.252; p = 0.594). No statistically significant between-region or within-region associations were detected. Year-adjusted regional means ranged from 6.82 to 15.03, and 83.1% of the remaining variance was between regions. Live-birth-weighted sensitivity analyses likewise detected no statistically significant association for the Gini coefficient (B = 0.013; 95% CI: −0.041 to 0.067; p = 0.640) or the P80/P20 ratio (B = − 0.021; 95% CI: −0.189 to 0.146; p = 0.803). No statistically significant association was detected between regional income inequality and IMR after accounting for year-specific effects and repeated observations. However, the confidence interval for the primary Gini estimate did not exclude small-to-moderate effects, so the findings should not be interpreted as evidence of no association. Persistent regional heterogeneity suggests that other demographic, social, and health-system factors may contribute to regional differences.