Relationship Between Daytime Versus Nighttime Continuous Glucose Monitoring Metrics with A1C in Adults with Type 1 Diabetes

Objective: To evaluate influence of daytime versus nighttime continuous glucose monitoring (CGM)-based metrics on A1C in adults with type 1 diabetes (T1D).Research Design and Methods: CGM data from 407 adults with T1D (age 39 +/- 15 years, diabetes duration 20 +/- 12 years, A1C 7.3% +/- 1.4% and 53% female) from two studies were included in this analysis. The association between daytime (6 AM-10.59 PM) and nighttime (11 PM-5.59 AM) CGM variables such as mean glucose, time in range (TIR; 70-180 mg/dL), time in tight target range (TTIR; 70-140 mg/dL), and time above range (TAR >180 mg/dL) was examined within five A1C categories (<7%, 7%-7.9%, 8%-8.9%, 9%-9.9%, and >= 10%).Results: Although mean glucose was increasing with higher A1C, there was no statistical difference in mean glucose between daytime versus nighttime within five A1C groups (143.2 +/- 22.7 vs. 143.6 +/- 25.0 for A1C <7%, 171.4 +/- 17.3 vs. 175.3 +/- 28.8 for A1C 7.0%-7.9%, 193.4 +/- 19.4 vs. 195.3 +/- 29.5 for A1C 8.0%-8.9%, 214.9 +/- 28.8 vs. 219.7 +/- 36.1 for A1C 9.0%-9.9% and 244.0 +/- 39.0 vs. 239.9 +/- 50.9 for A1C >= 10%, P > 0.05). Similarly, there was no difference between various CGM metrics by daytime versus nighttime within five A1C groups. Differences between five A1C groups' daytime versus nighttime mean glucose, TIR, TTIR, and TAR were also not statistically significant (all P > 0.05)Conclusion: Daytime versus nighttime glycemic control has similar influence on A1C in adults with T1D.