Study uses continuous glucose monitoring (CGM) systems to assess blood glucose levels during sleep.
Monitoring of blood glucose to near normal levels without hypoglycemia becomes a challenge in the management of diabetes. Even with the use of insulin pumps and long-acting insulin analogs, severe nocturnal hypoglycemia is common in patients with type 1 diabetes, especially in younger people. Data from previous studies of the Juvenile Diabetes Research Foundation (JDRF) have shown more than half of severe hypoglycemic events occurred during sleep and even greater incidence of severe nocturnal hypoglycemic events occur in patients with type 1 diabetes. In a newer study, the Juvenile Diabetes Research Foundation CGM randomized clinical trial, was conducted to characterize the amount of nocturnal hypoglycemia and evaluate factors associated with nocturnal hypoglycemia in adults and children with type 1 diabetes using retrospective and real-time continuous glucose monitoring (CGM) systems.
Anyone ages 8 to 72 years who has had type 1 diabetes for at least 1 year, uses either an insulin pump or multiple (at least three) daily insulin injections, and has an HbA1C level <10.0% was eligible to be included in this study. A total of 176 participants who met inclusion criteria were assigned to use either the FreeStyle Navigator (Abbott Diabetes Care, Alameda, CA) or the MiniMed Paradigm REAL-Time Insulin Pump and Continuous Glucose Monitoring System (Medtronic MiniMed, Northridge, CA). A blinded CGM device was used for 1 week at baseline. Thereafter, the unblinded CGM device was used daily. Researchers evaluated CGM dataset from midnight to 6:00 a.m. of 36,467 nights with ≥4 h of CGM glucose readings. A hypoglycemia event was defined as the occurrence of at least two CGM glucose values ≤60 mg/dl within a 20-minute period.
The study result shows that nocturnal hypoglycemia happens more frequently and is often prolonged in adults and children with type 1 diabetes with hypoglycemic events occurring 3,083 nights (8.5%) of the total 36,467 nights with the median percentage of nights with hypoglycemia per subject being 7.4% (interquartile range 3.7–12.1%). During 47% of the hypoglycemic nights, hypoglycemia events (glucose levels ≤60 mg/dl) occurred for at least 1 hour; for 23% of the nights, it occurred for at least 2 hours; and for 11% of the nights, it occurred for at least 3 hours. Only 3% of subjects had no hypoglycemic nights (number of nights for these subjects ranged from 55 to 235, their baseline HbA1c ranged from 7.7% to 8.9%). Moreover, the study reported a shorter mean duration of the hypoglycemic events in patients over 25 years old than in those less than 25 years old, this suggesting nocturnal hypoglycemia occurred more commonly in younger patients.
The study result also shows that patients with lower baseline HbA1c levels have a higher incidence of nocturnal hypoglycemia (P < 0.001). The frequency of nocturnal hypoglycemia was also greater in those who used blinded CGM for one week at baseline (P < 0.001). Nocturnal hypoglycemia was frequent and prolonged in the subjects even though nighttime CGM profiles were being used to adjust overnight basal rates, and long-acting insulin analog doses and sensor alarms were used to limit the duration of nocturnal hypoglycemic events.
Although the sensor of CGM could produce inaccuracy for hypoglycemic events some nights, an inpatient accuracy study conducted by the Diabetes Research in Children Network using the FreeStyle Navigator showed that the false-positive and false-negative rates for nocturnal hypoglycemia were approximately the same. Thus, the estimation of nocturnal hypoglycemia from the current study is unlikely to be affected by sensor inaccuracy.
- 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 a higher incidence of nocturnal hypoglycemia.
- Using blinded CGM for one week can help to identify patients who are at greater risk for nocturnal hypoglycemia.
Roy W. Beck. Prolonged Nocturnal Hypoglycemia Is Common During 12 Months of Continuous Glucose Monitoring in Children and Adults With Type 1 Diabetes. Diabetes Care. 2010 March 03.
Kay Lynn Tran, Doctor of Pharmacy Candidate: Class of 2018; LECOM College of Pharmacy