Incidence and predictors of diabetic retinopathy among patients with type 2 diabetes and hypertension: a 10-year retrospective follow-up study

Diabetes-related blindness creates a major challenge for the healthcare system due to its high treatment cost. The presence of type 2 diabetes has been associated with an increased risk of hypertension, and vice versa, and their coexistence increases the risk of diabetic retinopathy. Despite this fact, to date, most of the research on diabetic retinopathy in Northwestern Ethiopia has been limited and has not considered the diabetic patient comorbid with hypertension. The study aims to determine the incidence and its predictors among patients with type-2 diabetes and hypertension at Debre Markos comprehensive and specialized hospitals. An institution-based retrospective follow-up study was conducted among 600 patients with type 2 diabetes and hypertension between June 30/2014, and July 01/2023. Data were entered using Epidata version 4.6 and analyzed using STATA version 17. All variables with P-values less than 0.25 in the bi-variable analysis were considered for multivariable analysis. Parametric survival models were fitted, and the Weibull model was selected based on its lowest AIC and BIC. Multicollinearity was checked using VIF. Statistical significance was declared at 95% CI with a P-value less than 0.05. Patients were followed for different follow-up times: with a median follow-up period of 85.2 months (IQR: 25.1). The overall incidence density of diabetic retinopathy was 5.16 per 1,000 person-months (95% CI 4.33-6.14). Injection medication (AHR = 0.24, 95% CI [0.18, 0.31]) and treatment duration ≥ 6 years (AHR = 0.30, 95% CI [0.15, 0.65]) decreased the hazard of developing the event. Whereas, poor glycemic control (AHR = 1.87, 95% CI [1.66, 2.31]), age ≥ 60 years (AHR = 1.51, 95% CI [1.09, 2.12]), obesity (AHR = 2.04, 95% CI [1.63, 2.71]), glycated hemoglobin (AHR = 1.88, 95% CI [1.42, 2.71]), and family history of diabetes (AHR = 2.12, 95% CI [1.16, 4.11]) had increased the hazard of developing diabetic retinopathy. The findings indicate a substantial burden and earlier occurrence of diabetic retinopathy. Therefore, early and regular screening could be prioritized, particularly for high-risk groups such as older patients, those with poor glycemic control, obesity, and a family history of diabetes. Clinically, targeting HbA1c reduction, blood pressure control, and weight reduction interventions should be recommended at all follow-up visits.