Magnitude of the dawn phenomenon and its impact on the overall glucose exposure in type 2 diabetes: is this of concern?

Abstract

Objective: To assess the magnitude of the dawn phenomenon and its impact on the total glucose exposure in type 2 diabetes.

Research design and methods: A total of 248 noninsulin-treated persons with type 2 diabetes who underwent continuous glucose monitoring were divided into three groups selected by treatments: diet alone (n = 53); insulin sensitizers alone (n = 82); and insulin secretagogues alone or in combination with insulin sensitizers (n = 113). The dawn phenomenon (∂ glucose, mg/dL) was quantified by its absolute increment from nocturnal nadir to prebreakfast value. The participants were secondarily divided into two paired subsets after they had been separated by the presence/absence of a dawn phenomenon based on a threshold of 20 mg/dL and matched for glucose nadir. The impact of the dawn phenomenon was assessed on HbA1c and 24-h mean glucose.

Results: The median of ∂ glucose (interquartile range) was 16.0 (0-31.5 mg/dL) in the 248 subjects, and no differences were observed across groups selected by HbA1c or treatments. In the overall population, the mean impacts on HbA1c and 24-h mean glucose were 4.3 ± 1.3 mmol/mol (0.39 ± 0.12%) and 12.4 ± 2.4 mg/dL, respectively. The mean impact on 24-h mean glucose was not statistically different between those on diet alone (16.7 ± 5.9 mg/dL) compared with the two subsets treated with oral hypoglycemic agents (11.2 ± 5.3 and 8.5 ± 7.5 mg/dL).

Conclusions: The impact of the dawn phenomenon on overall glycemic control in type 2 diabetes, as depicted by the HbA1c level, was ∼0.4% and not eliminated by any of the currently available armamentarium of oral antidiabetes agents.

Figure 1

Steps used for analyzing the impact of the dawn phenomenon in the overall population and in the different groups selected by treatments. In the different groups including the overall population, the patients were secondarily separated into two paired subsets after selection for presence/absence of a dawn phenomenon (threshold set at 20 mg/dL) and after matching for nocturnal glucose nadir. Number of patients in each group and subset are indicated inside each square.

Figure 2

Mean averaged 24-h continuous glucose profiles in the two paired subsets of patients derived from either the overall population (A) (n = 68 in each subset) or the group treated with diet alone (B) (n = 15 in each subset). The subsets were selected after patients had been separated for the presence/absence of a dawn phenomenon. Solid curves, subsets of patients with the presence of a dawn phenomenon; dotted curves, subsets of patients with the absence of a dawn phenomenon.