Presence and development of diabetic retinopathy in 16 999 patients with type 1 diabetes in the Danish Registry of Diabetic Retinopathy

Purpose: To evaluate the five-year incidence of diabetic retinopathy (DR) and associated risk markers in patients with type 1 diabetes in the national Danish DR-screening programme. Methods: Based on national data, we included all 16 999 patients with type 1 diabetes in the Danish Registry of Diabetic Retinopathy, who attended the national screening programme in the period 2013–2018. According to the worse eye at first screening, DR was classified (levels 0–4) and linked with various national health registries to retrieve information on diabetes duration, systemic comorbidity, and medication. Results: At first screening, median age and duration of diabetes were 45.0 and 16.7 years, and 57.5% were males. The prevalence and five-year incidences for DR and progression to proliferative DR (PDR) were 44.2%, 8.9% and 2.0%, respectively. In multivariable Cox models, the incidence endpoints were associated with duration of diabetes (hazard ratio [HR] 1.76, 95% confidence interval [CI] 1.63–1.89, and HR 2.04, 95% CI 1.73–2.40 per 10 years), moderately low Charlson Comorbidity Index score (HR 1.27, 95% CI 1.10–1.47, and HR 2.80, 95% CI 2.23–3.51), and use of blood pressure lowering medication (HR 1.20, 95% CI 1.05–1.36, and HR 1.98, 95% CI 1.53–2.57). Conclusion: In a study of all patients with type 1 diabetes from the Danish DR-screening programme, we identified duration of diabetes, systemic disease and use of anti-hypertensive treatment as consistent risk markers for incident and progressive DR.