Analysis of prevalence, magnitude and timing of the dawn phenomenon in type 1 diabetes: descriptive analysis of two insulin pump trials

Abstract Objective 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 33 participants from two sensor-augmented insulin pump studies were analyzed. Twenty participants were obtained from a methodologically-ideal semi-automated 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 the individual trials using the standard definition of an increase in insulin exceeding 20% and lasting 90 minutes or more. Among cases, time of onset and percent change in the magnitude of basal delivery were determined. Results Seventeen participants (52%) experienced the dawn phenomenon [11/20 (55%) in the derivation set and 6/13 (46%) in the confirmation set]. Time of onset was 3:00 am [IQR; 3:00, 4:15 am] in the derivation set and 3:00 am [3:00, 4:00 am] in the confirmation set. The magnitude of the dawn phenomenon was a 58.1% [28.8, 110.6%] increase in insulin requirements in the derivation set and 65.5% [45.6%, 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 3am) and has substantial but highly variable magnitude. These findings imply that optimization of glycemic control requires clinical emphasis on fasted overnight basal insulin assessment.