Predictors of time to diabetic retinopathy in patients with type 2 diabetes mellitus: a survival analysis study

Diabetic retinopathy (DR) is a common complication of type 2 diabetes mellitus (T2DM) and a major cause of visual impairment. Despite the high prevalence of T2DM in Iran, longitudinal evidence on DR is limited. This study aimed to investigate the incidence and predictors of DR among patients with T2DM in Yazd, Iran. This retrospective cohort study used routinely collected clinical data from 753 adults with T2DM who attended the Diabetes Center of Yazd, Iran, between 2012 and 2024. Participants were followed from their first clinic visit until the development of DR, loss to follow-up, death, or the end of the study period. Kaplan–Meier survival analysis and Cox proportional hazards regression models were used to estimate time to DR and identify associated risk factors. Among 753 subjects with T2DM, 208 (27.6%) developed DR during follow-up. The overall incidence rate was 5.01 per 1,000 patient-months (95% CI: 4.37–5.74). The mean time to DR development was 99.23 months, with a median of 108 months. Also, increasing age (adjusted HR = 1.02; 95% CI: 1.002–1.04), longer duration of diabetes (adjusted HR = 1.03; 95% CI: 1.01–1.05), and higher HbA1c levels (adjusted HR = 1.20; 95% CI: 1.08–1.32) were significantly associated with increased risk of DR. Systolic blood pressure showed a borderline association after adjustment. Whereas lipid parameters were not significantly associated. Longer duration of diabetes, poor glycemic control, and older age were independently associated with an increased risk of DR. Systolic blood pressure showed a borderline association after adjustment, while lipid parameters were not significantly associated. These findings highlight the importance of early risk stratification and strict metabolic control to help prevent or delay DR.