Glycaemic control over lifespan impacts retinopathy risk

Children with type 1 diabetes need to maintain tight glycaemic control throughout their lives to reduce their risk of severe retinopathy in adulthood, new research suggests.

The retrospective data linkage study involving over 500 people with childhood onset type 1 diabetes diagnosed between 1975 and 2010 found that after adjusting for duration of diabetes, HbA1c levels throughout the course of life was independently associated with the risk of retinopathy in adulthood.

Writing in this week’s MJA the researchers led by Mary White from The Royal Children’s Hospital in Melbourne said their findings supported the adoption of a target of 58 mmol/mol or less in paediatric clinical practice.

The research team assigned each participant to one of four glycaemic control groups: ‘stable low’ (mean paed/adult HbA1c ≤ 66 mmol/mol); improving (mean paed HbA1c > 66 mmol/mol, mean adult HbA1c ≤ 66 mmol/mol); worsening (mean paed HbA1c ≤ 66 mmol/mol, mean adult HbA1c > 66 mmol/mol); or stable high (paed/ adult mean HbA1c > 66 mmol/mol).

Results showed that 4% of the ‘improving’, 1% of the ‘worsening’ and 7% of the ‘stable high’ groups developed severe diabetic retinopathy (SDR). No participants in the ‘stable-low’ group developed the complication.

Each 10.9 mmol/mol increase in paediatric and adult HbA1c level was associated with an almost three-fold and two-fold risk of SDR respectively.

Longer duration of type 1 diabetes was also associated with an increased risk of SDR (OR 1.3 per additional year).

“Our data indicate that both paediatric and adult mean HbA1c levels are modifiable factors that moderate this risk,” they wrote.

According to the authors this finding was important for paediatric care providers as 64.6% of the participants remained in the same HbA1c level category (low or high) during the paediatric and adult periods.

It also challenged the widely-held belief that glycaemic control in young adults with type 1 diabetes improved during their mid to late 20s following deterioration during the adolescent years.

“As severe retinopathy commenced during the third decade of life in our cohort and most people had similar glycaemic control levels in childhood and adulthood, the contribution of metabolic memory – the concept that hyperglycaemia appears to have a chronic rather than an acute effect on the development of complications – from the paediatric population was integral to this risk,” they added.

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