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.