The Frequency of Intermittently Scanned Glucose and Diurnal Variation of Glycemic Metrics

Background: The relation between the frequency of intermittently scanned continuous glucose monitoring (isCGM) and diurnal variation of time in range (TIR) and time below range (TBR) is unknown. Method: A total of 163 persons with type 1 diabetes who used isCGM had glucose data for 60 days downloaded. Mean TIR and median TBR were calculated for 15-minute periods and presented for daytime and nighttime. The values for tertiles of scanning frequency were compared. Results: The 1st tertile ( n = 53) of the population scanned <10 times; the 2nd tertile ( n = 56) 10-13 times, and the 3rd tertile ( n = 54) >13 per 24 hours. TIR (%, mean ± (SD)) increased significantly from the 1st to the 3rd scan tertile both during the day (43.8 ± 14.8, 52.0 ± 12.3, 62.1 ± 12.8) and the night (44.5 ± 17.3, 52.3 ± 18.5, 64.0 ± 13.9; P < .0001). In contrast, TBR (median, (IQR)) was not significantly associated with scan tertiles during daytime (3.5% (1.1-7.8), 4.4% (1.8-6.1), 3.5% (2.1-6.1); P = .85) or nighttime (3.8% (1.4-13.7), 5.0% (1.6-9.6), 5.7% (3.6-10.9); P = .24). In a multiple regression model, a 50% increase in 24-hour scanning frequency was associated with a 7.8 percentage point increase in TIR (95% CI, 5.6-10.0). Conclusions: Increased scanning frequency was associated with a higher TIR both during daytime and nighttime with no change in TBR.