The rise and fall of HbA_1c as a risk marker for diabetes complications

It is still unclear whether short-term, within-day, variability in glycaemic control is contributory to the development of diabetes micro- or macrovascular complications. However, consistent and compelling data are emerging that longer term fluctuations in glucose, as evidenced by increases in HbA_1c variability, do indeed add to the mean HbA_1c value in predicting the risk of microvascular disease. Until now, studies have found this to be the case mainly in type 1 diabetes, but in this issue of Diabetologia (DOI: 10.​1007/​s00125-012-2572-7) an analysis of the Tsukuba Kawai Diabetes Registry in Japan has found that HbA_1c variability also predicts the risk of nephropathy in type 2 diabetic patients. These observations raise the possibility that reducing rises and falls in HbA_1c may help avoid hyperglycaemia-related vascular disease without running the same risk of hypoglycaemia that a strategy focusing purely on lower HbA_1c might incur.