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 ≥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 ≤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 ≥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.