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 I 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 AlC, 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.