Academy of Medical Sciences of I.R. Iran Archives of Iranian Medicine 1029-2977 29 3 2026 03 01 Global Inequalities in Colorectal Cancer Incidence, Mortality, and Mortality-to-Incidence Ratio in Relation to Human Development Index: An Analysis Based on the Global Burden of Disease Study, 1990–2023 174 182 10.34172/aim.35654 EN Erfan Ayubi https://orcid.org/0000-0002-8829-9304 Salman Khazaei https://orcid.org/0000-0001-5918-2310 Journal Article 10.34172/aim.35654 2026 01 01 2026 02 27 Background: Over recent decades, colorectal cancer (CRC) burden measures have changed worldwide, showing variations associated with differences in the Human Development Index (HDI). The purpose of this study was to examine the relationship between HDI and CRC incidence, mortality, and the mortality-to-incidence ratio (MIR) from 1990 to 2023, and to explore HDI-related inequalities in these measures over time. Methods: Age-standardized CRC incidence and mortality rates from the Global Burden of Disease study were analyzed alongside HDI data from the UN. This ecological study used countries as units of analysis. The association between HDI and CRC indicators from 1990 to 2023 was assessed using Generalized Estimating Equations (GEE). HDI-related inequality in CRC indicators for 1990 and 2023 was measured with the Concentration Index (CI), and the contribution of HDI to temporal inequalities was evaluated via Blinder-Oaxaca decomposition analysis. Results: Global socioeconomic inequalities in CRC incidence (CI1990=0.28 vs. CI2023=0.27) and mortality (0.29 vs. 0.15) decreased significantly while inequality in MIR (-0.29 vs. -0.39) increased significantly from 1990 to 2023, with these trends varying according to HDI levels. Higher HDI was associated with increased CRC incidence and mortality across low to high HDI countries. However, in very high HDI countries (HDI>0.80), incidence continued to rise while mortality showed a declining trend, resulting in a substantially lower MIR. Spline analysis confirmed significant non-linear relationships with a threshold at HDI 0.80 (P<0.001). The strength of the association between HDI and CRC incidence and mortality decreased over time, especially in higher HDI countries (HDI>0.70). The distribution of HDI was associated with the reduction in MIR, especially among low (HDI<0.55) and very high HDI countries (HDI>0.80). Conclusion: Our study found evidence of an association between HDI distribution and temporal variations in CRC burden measures from 1990 to 2023.