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 HbA1c 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 HbA1c levels were calculated for the paediatric and adult periods. Four glycaemic control trajectories were defined according to mean paediatric and adult HbA1c levels: stable low (paediatric and adult HbA1c ≤ 66 mmol/mol); improving (paediatric HbA1c > 66 mmol/mol, adult HbA1c ≤ 66 mmol/mol); worsening (paediatric HbA1c ≤ 66 mmol/mol, adult HbA1c > 66 mmol/mol); and stable high (paediatric and adult HbA1c > 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 HbA1c 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 HbA1c levels, independent of glycaemic control during adulthood; it was not documented in patients with a stable low glycaemic control trajectory.