Prolonged nocturnal hypoglycemia is common during 12 months of continuous glucose monitoring in children and adults with type 1 diabetes.

OBJECTIVE: To characterize the amount of nocturnal hypoglycemia and evaluate factors associated with nocturnal hypoglycemia assessed with continuous glucose monitoring (CGM) in adults and children with type 1 diabetes who participated in the Juvenile Diabetes Research Foundation CGM randomized clinical trial.

RESEARCH DESIGN AND METHODS: The analysis included 36,467 nights with >or=4 h of CGM glucose readings between 12 midnight and 6:00 a.m. from 176 subjects assigned to the CGM group of the trial. The percentage of nights in which hypoglycemia occurred (two consecutive CGM readings <or=60 mg/dl in 20 min) was computed for each subject. Associations with baseline characteristics and clinical factors were evaluated using a multivariate regression model.

RESULTS: Hypoglycemic events occurred during 8.5% of nights, with the median percentage of nights with hypoglycemia per subject being 7.4% (interquartile range 3.7-12.1%). The duration of hypoglycemia was >or=2 h on 23% of nights with hypoglycemia. In a multivariate model, a higher incidence of nocturnal hypoglycemia was associated with 1) lower baseline A1C levels (P < 0.001) and 2) the occurrence of hypoglycemia on one or more nights during baseline blinded CGM (P < 0.001). The hypoglycemia frequency was not associated with age or with insulin modality (pump versus multiple daily injections).

CONCLUSIONS: Nocturnal hypoglycemia is frequent and often prolonged in adults and children with type 1 diabetes. Patients with low A1C levels are at an increased risk for its occurrence. One week of blinded CGM can identify patients who are at greater risk for nocturnal hypoglycemia.