Age at Onset and the Risk of Proliferative Retinopathy in Type 1 Diabetes

OBJECTIVE: Age at onset of type 1 diabetes influences the risk of microvascular complications. However, the long-term risk of proliferative retinopathy within the wide spectrum of age at onset of type 1 diabetes is less well known. RESEARCH DESIGN AND METHODS: A sample of 1,117 consecutively recruited patients was drawn from the FinnDiane Study population (4,800 patients). Type 1 diabetes was defined as age at onset ≤40 years, insulin treatment initiated within 1 year, and C-peptide ≤0.3 nmol/l. Retinopathy status was graded based on ophthalmic records and/or fundus photographs. The risk of proliferative retinopathy was studied in age-at-onset groups 0–4, 5–14, and 15–40 years. RESULTS: The mean durations to proliferative retinopathy were 24.3 (22.7–25.9) years in the 0–4 years group, 20.1 (19.2–21.1) years in the 5–14 years group, and 21.6 (19.8–23.3) years in the 15–40 years group (P < 0.001). In a Cox regression model, with A1C, blood pressure, sex, and BMI as covariates, the highest risk of proliferative retinopathy was observed in the 5–14 years group (hazard ratio 1.90 [95% CI 1.45–2.48], P < 0.001). Diabetes onset 0–4 vs. 5–14 years made no difference in the long-term risk of proliferative retinopathy (P = 0.2). When split into two groups, age at onset <15 years was associated with a higher long-term risk than age at onset ≥15 years (1.82 [1.40–2.36], P < 0.001). CONCLUSIONS: Age at onset significantly modifies the long-term risk of proliferative retinopathy. The highest risk is in age-at-onset group 5–14 years, whereas the lowest risk is in age-at-onset group 15–40 years.