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Thalassemia imposes a substantial and unequal global health burden, yet its temporal evolution stratified by sociodemographic development remains incompletely characterized using the most recent Global Burden of Disease (GBD) data. Using GBD 2023 data, we analyzed incidence, prevalence, deaths, and disability-adjusted life years (DALYs) for thalassemia across five Socio-Demographic Index (SDI) quintiles from 1990 to 2023. Age-standardized rates and absolute counts were extracted from the IHME GBD Results Tool. Joinpoint regression was applied to identify statistically significant inflection points and calculate average annual percentage changes (AAPCs) and annual percentage changes (APCs) for each burden indicator across SDI strata. Age-standardized mortality and DALY rates declined significantly across all SDI groups, with the largest reductions in high SDI (AAPC: −4.12% and − 4.20%, respectively) and high-middle SDI regions (AAPC: −3.86% and − 3.93%). By contrast, low SDI regions experienced a 16% rise in absolute deaths and a 66% surge in absolute prevalence, reaching 321,005 cases by 2023. The low-middle SDI group was the only stratum with a statistically significant net increase in age-standardized incidence (AAPC: +0.12%). Joinpoint analysis revealed non-linear, multi-phase trajectories across all strata, with recent reversals in incidence and prevalence rates in low and low-middle SDI regions. By 2023, a nearly six-fold disparity in age-standardized death and DALY rates persisted between the highest and lowest SDI quintiles. Thalassemia burden has declined substantially in high-SDI settings, driven by advances in prevention, screening, and treatment. However, low and low-middle SDI regions continue to face rising absolute burdens and recent trend reversals, underscoring critical inequities in access to care. Targeted, equitable strategies including expanded premarital screening, strengthened blood supply systems, and health system investment are urgently needed to close the persistent SDI-linked gap in thalassemia outcomes.