Impact of flash glucose monitoring on glycemic control varies with the age and residual β‐cell function of patients with type 1 diabetes mellitus

AIMS/INTRODUCTION: We aimed to explore the clinical factors associated with glycemic variability (GV) assessed with flash glucose monitoring (FGM), and investigate the impact of FGM on glycemic control among Chinese type 1 diabetes mellitus patients in a real‐life clinical setting. MATERIALS AND METHODS: A total of 171 patients were included. GV was assessed from FGM data. A total of 110 patients wore FGM continuously for 6 months (longitudinal cohort). Hemoglobin A1c (HbA1c), fasting and 2‐h postprandial C‐peptide, and glucose profiles were collected. Changes in HbA1c and glycemic parameters were assessed during a 6‐month FGM period. RESULTS: Individuals with high residual C‐peptide (HRCP; 2‐h postprandial C‐peptide >200 pmol/L) had less GV than patients with low residual C‐peptide ( 2‐h postprandial C‐peptide ≤200 pmol/L; P < 0.001). In the longitudinal cohort (n = 110), HbA1c and mean glucose decreased, time in range (TIR) increased during the follow‐up period (P < 0.05). The 110 patients were further divided into age and residual C‐peptide subgroups: (i) HbA1c and mean glucose were reduced significantly only in the subgroup aged ≤14 years during the follow‐up period, whereas time below range also increased in this subgroup at 3 months (P = 0.047); and (ii) HbA1c improved in the HRCP subgroup at 3 and 6 months (P < 0.05). The mean glucose decreased and TIR improved significantly in the low residual C‐peptide subgroup; however, TIR was still lower and time below range was higher than those of the HRCP subgroup at all time points (P < 0.05). CONCLUSIONS: HRCP was associated with less GV. FGM wearing significantly reduced HbA1c, especially in pediatric patients and those with HRCP. Additionally, the mean glucose and TIR were also found to improve.