A1c, glucose variability and hypoglycemia risk in patients with type 1 diabetes

The aim of this paper was to compare the predictive value of glycated hemoglobin (A1c) and glucose variability (GV) in the risk of hypoglycemia in patients with type 1 diabetes (T1D).

Analysis of continuous glucose monitoring performed in 130 T1D patients with a diabetes background of 17.1±8.6 years, in intensive insulin therapy (49.8±17.9 UI per day). Mean interstitial glucose (in mg/dL), GV (standard deviation of mean glucose, in mg/dL), time per day spent in hypoglycemia (interstitial glucose ≤70 mg/dL, in %), and episodes of asymptomatic or nocturnal hypoglycemia, (hypoglycemia between midnight and 8 a.m., in %), were assessed. Patients were divided into two groups: group I (N.=84) with A1C≤7.5% and group II (N.=46) with A1C>7.5%. A statistical analysis was performed using SPSS, version 21.0®.

Group I presented a significantly lower mean glucose (139.2±25.9 vs. 173.1±33.2 mg/dL, P<0.05) and GV (58.4±18.8 vs. 70.3±18.6 mg/dL, P<0.05) and more hypoglycemia time (7.65±7.04 vs. 5.35±5.64%, P<0.05). The number of patients with nocturnal hypoglycemia was not significantly different in both groups (8.7 vs. 5.8%, P>0.05). Hypoglycemia time was positively correlated with GV (r=0.23, P=0.01) and negatively with A1C and mean glucose (r=-0.23 and r=-0.36; P=0.01). In multivariate analysis, GV and mean glucose were associated with hypoglycemia time (β=0.22 and β=-0.15, P<0.01, respectively), independent of A1c, diabetes duration and insulin dose; nocturnal hypoglycemia was only associated with mean glucose (OR=0.9, P<0.05) and was associated with a 16-fold increased risk of asymptomatic hypoglycemia (OR: 16.9, P<0.01).

Patients with high HbA1c still remain at risk of hypoglycemia. Glucose variability independently predicts daily time spent in hypoglycemia. At night, hypoglycemia only correlates with mean glucose, suggesting that daily fluctuations are probably due to inadequate meals insulin coverage. The potential of GV for predicting hypoglycemia time supports the inclusion of measures of GV into a global diabetes strategy.