Tehran University of Medical Sciences Journal of Biostatistics and Epidemiology 2383-4196 10 3 2025 02 09 374 395 Sedigheh Mafakheri 1. Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran Erfan Ayubi Cancer Research Center, Hamadan University of Medical Sciences, Hamadan, Iran Shiva Borzouei 4. Department of Internal Medicine, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran Vajiheh Ramezani Doroh 6. Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran Salman Khazaei Hamadan University of Medical Sciences 2024 08 28 2024 12 28 Background: In Iran, evidence regarding the impact of socioeconomic (SES) inequality on the progression and complications of type 2 diabetes mellitus (T2DM) are sparse and needs growing body of research. SES is a complex construct and its impact on the health outcomes should be evaluated in an efficient and flexible way. The purpose of this study is to examine SES inequality in chronic complications among T2DM patients using methods of decomposing inequality. Methods: This cross-sectional study included patients with T2DM receiving care at the diabetes clinic in Hamadan City, Iran, between April and September 2023. Demographic, SES, diabetic related factors were obtained from medical records and face-to-face interviews. A binary logistic regression model was utilized to investigate the relationship between diabetes complications and independent variables. The concentration index (CI) and decomposition approach were used to evaluate SES inequality and determine the contribution of each factor to inequality. Results: A total of 530 patients (61.6% females and 54.9% less than 60 years) were included. In the study population, 22.3%, 9.5%, and 4.7% had retinopathy, kidney failure, and diabetic foot ulcers, respectively. The CI for retinopathy, kidney failure, and foot ulcers were [(CI: -0.273, p<0.001), (CI: -0.089, p<0.001), (CI: -0.122, p<0.001), respectively]. Factors with the greatest contribution to SES inequality for retinopathy were economic status (44.6%), duration of T2DM (24.5%), age (18.7%), and healthy lifestyle (12.5%), for kidney failure were economic status (33.8%), hypertension (22.5%), education level (21.3%), and HbA1c value (13.5%), and for foot ulcers were economic status (78.7%), duration of T2DM (33.6%), HbA1c value (17.2%) hypertension (7.4%). Conclusion: This study demonstrated that SES inequality in chronic complications of T2DM with greatest contribution for economic status. It is recommended that policymakers and health professionals consider the main causes of SES inequality in the chronic complications of T2DM when developing health strategies. https://jbe.tums.ac.ir/index.php/jbe/article/view/1492