The Association Between Mean Glycated Haemoglobin or Glycaemic Variability and the Development of Retinopathy in People with Diabetes: A Retrospective Observational Cohort Study.

ABSTRACT

INTRODUCTION: To determine the association between mean glycated haemoglobin (HbA1c) or glycaemic variability and the development of diabetic retinopathy (DR) in people with diabetes. METHODS: An observational cohort study with people registered with a DR eye screening service between October 2012 and October 2017. Those who had no DR at the start of the study were followed for a maximum of 5 years. HbA1c measures were used to calculate HbA1c variability and mean HbA1c to assess any relationship between these and the risk of developing new onset DR. RESULTS: A total of 2511 individuals were followed up for up to 5 years. Of these, 542 (21.6%) developed DR. After adjustment, HbA1c variability was not significantly associated with the development of DR (p = 0.3435). However, the mean HbA1c was (p < 0.0001). Those with type 1 diabetes had an odds of 1.63 (95% CI 1.11-2.40) of a retinopathy diagnosis compared to those with type 2 diabetes. CONCLUSIONS: We have shown that mean HbA1c is associated with an increased risk of developing diabetic retinopathy. However, after adjustment for sex, age, diabetes type and the mean, the HbA1c variability no longer remained significant. Our data suggest that optimizing long-term glycaemic control remains paramount.

It has been known for a long time that if an individual's diabetes is not as well controlled as it could be, then they are at increased risk of developing complications over many years. These complications include diabetes-related eye disease (retinopathy). For many years, the way of measuring how well someone's diabetes was controlled was by measuring glycated haemoglobin (HbA1c) which looked at how much glucose was attached to a red cell. This study looked at whether variation in HbA1c over 5 years of follow-up was associated with greater risk of developing retinopathy, and if this relationship was stronger than just measuring HbA1c alone. Previous work has shown that people with greater variation in HbA1c are at increased risk of poor wound healing in those with diabetes-related foot ulcers. The present study looked at 2511 people who had no diabetes-related eye disease at the start of the study and who had been followed for 5 years. We found that variability in HbA1c was not associated with an increased risk of developing diabetes-related eye disease, but confirmed that the average HbA1c had the strongest relationship. Our data confirm that the focus of preventing diabetes-related eye disease should be on lowering HbA1c.