ESPE Yearbook of Paediatric Endocrinology

To read the full abstract: Diabetes Care. 2018;41:326-332

The question whether or not T1DM patients with low HbA1c levels, which are thought to characterize good metabolic control, in fact experience hypoglycemia and most importantly severe hypoglycemia more frequently than T1DM patients with high HbA1c levels and hence worse metabolic control has been discussed controversially. However, it is commonly agreed upon that many patients with well controlled diabetes as reflected by low HbA1c levels suffer from a lower number of hypoglycemia. Importantly, the number of severe hypoglycemic episodes is reduced in people with well controlled diabetes. Diabetes education, the knowledge of hypoglycemia risk factors and adherence to treatment protocols as well as frequent blood glucose monitoring and adjustment of insulin doses are all thought to reduce the risk of hypoglycemia in patients with good metabolic control.

Here, continuous glucose monitoring data was used to assess the time spent in hypoglycemia as defined glucose levels below 3.9, 3.3, 3.0, or 2.8 mmol/L. Lower HbA1c values were associated with increased hypoglycemia risk, although the magnitude of risk depended upon the biochemical definition of hypoglycemia applied. The authors conclude, that real-time CGM may reduce the percentage time spent in hypoglycemia, and that this might change the relationship between HbA1c and hypoglycemia.

However, many other studies have shown that people with diabetes who know the risk of, and are able to prevent, hypoglycemia adequately have in fact lower HbA1c levels and are in good metabolic control. This provides evidence for the fact that diabetes education and treatment adherence leads to good metabolic control which is reflected by in fact both low HbA1c and at the same time a low rate of hypoglycemia episodes. The strength of this study may be seen in the fact that different definitions/biochemical thresholds of low blood sugar were analyzed and attention is drawn to the very fact that previous studies which were comparing HbA1c levels and hypoglycemia risk might have used different definitions and therefore had to arrive at different conclusions: if only very low blood sugar levels are considered as reflecting hypoglycemia people who know their diabetes and measure their blood sugar levels often will have less hypoglycemia episodes and at the same time exhibit low HbA1cs. This is reassuring for those who emphasize the importance to achieve good metabolic control as reflected by low HbA1c levels even in young children.