The Dawn Phenomenon across the Glycemic Continuum: Implications for Defining Dysglycemia.

AIMS To investigate the frequency of dawn phenomenon (DP) and its relationship with time in range (TIR) and glycemic variability (GV) using continuous glucose monitoring (CGM). METHODS 781 subjects of a multicenter CGM study in China were included: those with normal glucose tolerance (NGT n=360); impaired glucose regulation (IGR n=173); newly diagnosed type 2 diabetes mellitus (T2D n=248). Analysis of the magnitude of DP (ΔG) was conducted with the primary definition of 1.11 mmol/L and a secondary definition of 0.56 mmol/L. RESULTS The frequency of DP was 8.9%, 30.1% and 52.4% in NGT, IGR and T2D group, respectively, using the primary definition. In all three groups, TIR was lower (all P<0.05), coefficient of variation (CV) was higher in DP subgroup (all P<0.05). In DP subgroup of T2D, TIR was 7.0% (1.68h) lower and CV was 3.0% higher, and HbA1c was 0.6% (7 mmol/mol) higher using the primary definition (all P<0.05). CONCLUSIONS DP was present in a high percent of subjects with NGT and IGR. In newly diagnosed T2D group, the presence of DP was associated with poorer overall glycemic control.