Long term risk of severe retinopathy in childhood-onset type 1 diabetes: a data linkage study

Objectives: To determine the relationship between glycaemic control trajectory and the long term risk of severe complications in people with type 1 diabetes mellitus, as well as the effects of paediatric and adult HbA1_c levels.

Design, setting, participants: Data linkage study of data for adults with childhood-onset type 1 diabetes (diagnosed during 1975-2010) who had transitioned from paediatric diabetes care at the Royal Children's Hospital (Melbourne) to adult diabetes care at the Royal Melbourne Hospital during 1992-2013.

Main outcome measures: Severe complications were categorised as severe diabetic retinopathy (SDR), chronic kidney disease, ulceration or amputation, and death. Mean HbA1_c levels were calculated for the paediatric and adult periods. Four glycaemic control trajectories were defined according to mean paediatric and adult HbA1_c levels: stable low (paediatric and adult HbA1_c ≤ 66 mmol/mol); improving (paediatric HbA1_c > 66 mmol/mol, adult HbA1_c ≤ 66 mmol/mol); worsening (paediatric HbA1_c ≤ 66 mmol/mol, adult HbA1_c > 66 mmol/mol); and stable high (paediatric and adult HbA1_c > 66 mmol/mol).

Results: 503 eligible participants (253 men) were identified, 26 (5.2%) of whom had at least one severe complication, including 16 with SDR (3.2%). No-one in the stable low group, but 4% of the improving, 1% of the worsening, and 7% of the stable high groups developed SDR. Higher mean paediatric (per 10.9 mmol/mol increase: odds ratio [OR], 2.9; 95% CI, 1.9-4.3; P < 0.01) or adult HbA1_c levels (OR, 2.1; 95% CI, 1.4-3.1; P < 0.01) were associated with increased risk of SDR, as was longer duration of type 1 diabetes (per additional year: OR, 1.3; 95% CI, 1.2-1.5; P < 0.01).

Conclusion: SDR was associated with higher paediatric HbA1_c levels, independent of glycaemic control during adulthood; it was not documented in patients with a stable low glycaemic control trajectory.