Le phénomène de l'aube dans le diabète de type 2 : important ou accessoire ?

Since its discovery in the early 80's, the dawn phenomenon is depicted as a spontaneous rise in plasma glucose at the end of the overnight fast. On the basis of published studies, the most consistent definition is a dawn increase in glucose level greater than 10 mg/dl from the nocturnal glucose nadir to the prebreakfast glucose value. According to this definition the frequency is approximately of 60% in persons with type 2 diabetes (T2DM). At present, it remains difficult to identify the factors that can predict the absence/presence of this phenomenon. During many years some clinicians, on the basis of either speculative arguments or poorly-documented studies, have claimed that the dawn phenomenon does not occur in elderly patients. However, recent data indicate that its frequency and magnitude is the same in elderly as in younger subjects. One of the questions is to know first whether the dawn phenomenon and its consequence the “extended dawn phenomenon” are the “weak links” of the glycemic control of T2DM and secondly whether both phenomena contribute significantly or not to the overall glucose exposure, i.e., to HbA1c levels. A significant impact on HbA1c would justify therapeutic strategies aimed at achieving normal or near normal glucose levels at fasting. In contrast a mild or moderate impact would suggest less stringent objectives. It is highly likely that the truth is between these two positions. This represents an additional argument for a patient-centered approach in the management of hyperglycemia of T2DM. Such a strategy has been the subject of a Position Statement, recently published by a joint committee of experts of the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD).