Prevalence and consequences of nocturnal hypoglycemia among conventionally treated children with diabetes mellitus

To determine the prevalence and predictors of, and the glucose responses after, nocturnal hypoglycemia, we studied 135 pediatric patients with insulin-dependent diabetes mellitus on 388 nights. The frequencies of blood glucose values less than 60, 50, and 40 mg/dl (3.3, 2.8, and 2.2 mmol/L) at 2 am were 14.4%, 7.0%, and 2.1%, and at 6 am were 6.7%, 2.6%, and 0.5%, respectively. Longer duration of diabetes, higher daily insulin doses, and lower glycosylated hemoglobin values were all significant but weak predictors of 2 am hypoglycemia (glucose ≤60 mg/dl (≤3.3 mmol/L). A 10 pm glucose concentration ≤100 mg/dl (≤5.6 mmol/L) was present on 48% of nights with 2 am glucose values ≤60 mg/dl (≤3.3 mmol/L), but only 24% of nights with 10 pm blood glucose values ≤100 mg/dl (≤5.6 mmol/L) were followed by 2 am hypoglycemia. After treatment of 70 episodes of 2 am glucose concentrations ≤60 mg/dl (≤3.3 mmol/L), mean 6 am glucose concentration was 95±6 mg/dl (5.7±0.3 mmol/L) and ≤100 mg/dl in 68.6%. In only 4.3% of these cases was the 6 am glucose concentration >200 mg/dl (>11.1 mmol/L). Among patients who experienced 2 am hypoglycemia, after-breakfast glucose values were not greater on days with 2 am hypoglycemia than on days without it. These data indicate that 2 am hypoglycemia is relatively common in patients with insulin-dependent diabetes mellitus, is frequently preceded by a 10 pm glucose value ≤5.6 mmol/L, and is less well predicted by other factors. Appropriate treatment of 2 am hypoglycemia seldom results in either before-breakfast or after-breakfast blood glucose values >200 mg/dl (>11.1 mmol/L). Early-morning hypoglycemia is an uncommon cause of otherwise unexplained, prebreakfast hyperglycemia in children with insulin-dependent diabetes mellitus.