Longer duration of diabetes, poor glycemic control, and older age were independently associated with an increased risk of diabetic retinopathy, highlighting the importance of early risk stratification and strict metabolic control to help prevent or delay DR.
Key Findings
Results
Among 753 patients with T2DM, 208 (27.6%) developed diabetic retinopathy during the follow-up period.
Retrospective cohort study using routinely collected clinical data from the Diabetes Center of Yazd, Iran, between 2012 and 2024.
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.
Participants were followed from their first clinic visit until DR development, loss to follow-up, death, or end of study period.
Results
Increasing age was significantly associated with an increased risk of developing diabetic retinopathy.
Adjusted hazard ratio for age: HR = 1.02 (95% CI: 1.002–1.04).
This association remained significant after multivariable adjustment using Cox proportional hazards regression.
Each additional year of age corresponded to a 2% increase in the hazard of DR development.
Results
Longer duration of diabetes was significantly associated with an increased risk of diabetic retinopathy.
Adjusted hazard ratio for diabetes duration: HR = 1.03 (95% CI: 1.01–1.05).
Each additional month or year of diabetes duration corresponded to a 3% increase in the hazard of DR development.
Duration of diabetes remained an independent predictor after adjustment for other covariates.
Results
Higher HbA1c levels were significantly associated with an increased risk of diabetic retinopathy.
Adjusted hazard ratio for HbA1c: HR = 1.20 (95% CI: 1.08–1.32).
Each unit increase in HbA1c corresponded to a 20% increase in the hazard of DR development.
HbA1c was the strongest individual predictor among the significant risk factors identified.
Poor glycemic control was identified as an independent predictor of DR after multivariable adjustment.
Results
Systolic blood pressure showed a borderline association with diabetic retinopathy after multivariable adjustment.
The association was described as 'borderline' after adjustment, meaning it did not reach conventional statistical significance thresholds.
Systolic blood pressure did not emerge as a statistically significant independent predictor in the fully adjusted Cox model.
Lipid parameters were not significantly associated with DR risk in any model.
Results
Lipid parameters were not significantly associated with the risk of developing diabetic retinopathy.
Lipid parameters were tested as potential predictors in both unadjusted and adjusted Cox proportional hazards models.
No significant association was found between lipid parameters and time to DR development.
This finding contrasts with the significant associations observed for glycemic and demographic variables.
Methods
Kaplan-Meier survival analysis and Cox proportional hazards regression were used to estimate time to DR and identify risk factors in this retrospective cohort.
The study included 753 adults with T2DM attending the Diabetes Center of Yazd, Iran.
Data were collected retrospectively from routine clinical records spanning 2012 to 2024.
The study noted that longitudinal evidence on DR is limited despite the high prevalence of T2DM in Iran.
The study population was drawn from a single diabetes center in Yazd, Iran, which may limit generalizability.
What This Means
This research examined what factors predict whether and how quickly people with type 2 diabetes develop diabetic retinopathy (damage to the eyes that can lead to vision loss). Researchers followed 753 patients in Iran over up to 12 years and found that more than a quarter of them (27.6%) developed diabetic retinopathy during the study period. On average, it took about 8 to 9 years from the first clinic visit for retinopathy to develop.
The study found three main factors that independently increased the risk of developing diabetic retinopathy: older age, having had diabetes for a longer time, and having higher blood sugar levels (measured by HbA1c). Among these, poor blood sugar control had the largest effect — each unit increase in HbA1c was associated with a 20% higher risk of developing retinopathy. Blood pressure showed a weak, borderline association with retinopathy risk, and cholesterol and other lipid levels were not significantly linked to retinopathy in this study.
This research suggests that keeping blood sugar well-controlled and identifying high-risk patients early — particularly those who are older or have had diabetes for many years — may be important strategies for preventing or delaying vision-threatening complications of diabetes. The findings reinforce the value of regular eye screening and strict management of blood glucose levels in people living with type 2 diabetes.
Foroozanfar Z, Ghadiri-Anari A, Azizi R, Mehrabbeik A. (2026). Predictors of time to diabetic retinopathy in patients with type 2 diabetes mellitus: a survival analysis study.. BMC ophthalmology. https://doi.org/10.1186/s12886-026-05260-3