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.