The relationship between HbA1c values and the occurrence of hypoglycemia as assessed by continuous glucose monitoring in patients with type 1 diabetes

BACKGROUND: We aimed to examine the relationship between the occurrence of hypo-/hyperglycemia and HbA1c values, as assessed by continuous glucose monitoring (CGM) in patients with type 1 diabetes. METHODS: The study subjects comprised 101 type 1 diabetic patients on basal-bolus insulin therapy, who were put on masked CGM immediately after admission. The subjects were divided into four groups equally by HbA1c values and the 24-h CGM data were compared among the groups. RESULTS: Groups A to D comprised 24 patients with HbA1c ≤7.2 %, 26 patients with 7.2 % <HbA1c ≤8.2 %, 27 patients with 8.2 % <HbA1c ≤9.2 %, and 24 patients with HbA1c >9.2 %, respectively. The higher the HbA1c values, the significantly higher the 24-h mean glucose levels [median (25–75 percentiles)], with the HbA1c in groups A to D being 133 (114–155), 158 (132–188), 182 (152–206), and 186 (143–215) mg/dL, respectively (P < 0.001). Conversely, the higher the HbA1c values, the significantly shorter the time in hypoglycemia (<70 mg/dL), with the time in groups A to D being 170 (58–341), 78 (0–210), 45 (0–105), and 20 (0–105) min, respectively (P = 0.014); and the higher the HbA1c values, the significantly shorter the time in nocturnal hypoglycemia, with the time in groups A to D being 120 (5–269), 25 (0–120), 0 (0–60), and 0 (0–89) min, respectively (P = 0.019). No significant difference was seen between groups A to D in the standard deviations (SDs) of 24-h glucose values at 53 (40–65), 54 (45–70), 64 (55–76), and 58 (48–80), respectively. CONCLUSION: In type 1 diabetic patients, lower HbA1c was not associated with lower SD of 24-h glucose values, but may result in increased hypoglycemia. Trial Registration Current controlled trials UMIN000019190