Nocturnal hypoglycemia detected with the Continuous Glucose Monitoring System in pediatric patients with type 1 diabetes.

OBJECTIVE

To use the Continuous Glucose Monitoring System (CGMS, MiniMed, Sylmar, Calif) to determine if bedtime blood glucose levels were associated with the occurrence of nocturnal hypoglycemia.

STUDY DESIGN

Patients (n = 47, 18 boys, mean age 11.8 +/- 4.6 years) with type 1 diabetes used CGMS for 167 nights. Data were analyzed for glucose </=40 or </=50 mg/dL, comparing bedtime blood glucose levels of </=100 or >100 mg/dL and </=150 or >150 mg/dL.

RESULTS

A glucose value of </=40 mg/dL occurred on 27% of nights and </=50 mg/dL on 35% of nights. There was a 2-fold increase (45% vs 22%, P =.015) in the incidence of hypoglycemia with a bedtime glucose </=100 mg/dL and a 1.7-fold increase (46% vs 26%, P =.01) with a value of </=150 mg/dL; most episodes occurred between 9 PM and 1 AM. There was no difference in hypoglycemia duration (86.4 minutes for glucose </=100 mg/dL vs 84.5 minutes for >100 mg/dL, P = NS), and no bedtime glucose value between 110 and 300 mg/dL decreased the incidence of nocturnal hypoglycemia to </=10%. The incidence of nocturnal hypoglycemia was similar for patients using insulin pump and injection therapy, and there was no correlation between hemoglobin A1c and incidence or duration of hypoglycemia.

CONCLUSIONS

Nocturnal hypoglycemia is frequent, of long duration, associated with bedtime glucose values </=100 to 150 mg/dL, and predominately in the early part of the night. CGMS is a useful tool to diagnose asymptomatic nocturnal hypoglycemia.