Analysis of Prevalence, Magnitude and Timing of the Dawn Phenomenon in Adults and Adolescents With Type 1 Diabetes: Descriptive Analysis of 2 Insulin Pump Trials.

OBJECTIVES: To better understand the dawn phenomenon in type 1 diabetes, we sought to determine its prevalence, timing and magnitude in studies specifically designed to assess basal insulin requirements in patients using insulin pumps. METHODS: Thirty-three participants from 2 sensor-augmented insulin pump studies were analyzed. Twenty participants were obtained from a methodologically ideal semiautomated basal analysis trial in which basal rates were determined from repeated fasting tests (the derivation set) and 13 from an artificial pancreas trial in which duration of fasting was variable (the "confirmation" set). Prevalence was determined for the total cohort and for individual trials using the standard definition of an increase in insulin exceeding 20% and lasting ≥90 minutes. Among cases, time of onset and percent change in the magnitude of basal delivery were determined. RESULTS: Seventeen participants (52%) experienced the dawn phenomenon (11 of 20 [55%] in the derivation set and 6 of 13 [46%] in the confirmation set). Time of onset was 3 AM (interquartile range [IQR], 3 to 4:15 AM) in the derivation set and 3 AM (IQR, 3 to 4 AM) in the confirmation set. The magnitude of the dawn phenomenon was a 58.1% (IQR, 28.8% to 110.6%) increase in insulin requirements in the derivation set and 65.5% (IQR, 45.6% to 87.4%) in the confirmation set. CONCLUSIONS: The dawn phenomenon occurs in approximately half of patients with type 1 diabetes; when present, it has predictable timing of onset (generally 3 AM) and a substantial, but highly variable, magnitude. These findings imply that optimization of glycemic control requires clinical emphasis on fasted overnight basal insulin assessment.

Single- and Dual-Hormone Artificial Pancreas for Overnight Glucose Control in Type 1 Diabetes.

CONTEXT: The added benefit of glucagon in artificial pancreas systems for overnight glucose control in type 1 diabetes has not been fully explored. OBJECTIVE: The objective of the study was to compare the efficacy of dual-hormone (insulin and glucagon) artificial pancreas, single-hormone (insulin alone) artificial pancreas, and conventional insulin pump therapy. DESIGN: This study was a three-center, three-arm, open-label, randomized, crossover controlled trial involving three interventions, each applied over a night after a high carbohydrate/high fat meal and a second after exercise to mimic real-life glycemic excursions. SETTING: The study was conducted in a home setting. PATIENTS: Twenty-eight type 1 diabetes participants (21 adults and seven adolescents) participated in the study. INTERVENTIONS: Dual-hormone artificial pancreas, single-hormone artificial pancreas, and conventional pump therapy was activated from 9:00 PM to 7:00 AM. MAIN OUTCOME: The main outcome was a proportion of time in target (4-8 mmol/L) by continuous glucose monitoring from 11:00 PM to 7:00 AM. Analysis was by intention to treat. RESULTS: The median (interquartile range) percentage of time-in-target glucose range was 47% (36%-71%) for conventional therapy, higher on both single-hormone (76% [65%-91%], P < .001) and dual-hormone artificial pancreas (81 [68%-93%], P < .001). The median (interquartile range) time spent below 4 mmol/L was 14% (4%-28%) for conventional therapy, lower on both single-hormone (5% [0%-13%], P = .004) and dual-hormone artificial pancreas (1% [0%-8%], P < .001). There were 14 hypoglycemic events on conventional therapy compared with six incidences on the single-hormone artificial pancreas (P = .059) and three incidences on the dual-hormone artificial pancreas (P = .017). None of these outcomes differed significantly between single- and dual-hormone configurations. CONCLUSIONS: Single- and dual-hormone artificial pancreas systems both provided better glucose control than conventional therapy. Although the dual-hormone configuration did not increase overnight time-in-target glucose levels, an effect on lowering hypoglycemia risk cannot be ruled out.