Diurnal variation in the association between the scan frequency of isCGM and CGM metrics: post hoc analysis of the ISCHIA study

Background and aims: To investigate the association between the frequency of intermittent-scanning continuous glucose monitoring (isCGM) and diurnal variation of time in range (TIR), time above range (TAR), and time below range (TBR), we performed a post hoc analysis of the ISCHIA study, a multicenter, prospective, open-label, randomized crossover study of patients with type 1 diabetes mellitus. Method: Data of 93 people who completed the ISCHIA study were used. We calculated scan frequency, TAR, TIR, and TBR of four approximately 6-h intervals: 6:00–11:59 (morning), 12:00–17:59 (afternoon), 18:00–23:59 (evening), and 0:00–5:59 (night). The correlation between scan frequency and diurnal variation of CGM metrics was analyzed using nonparametric Spearman correlation analysis. Results: More frequent scanning was associated with higher TIR in the afternoon (rho = 0.343, P < 0.001), evening (rho = 0.243, P = 0.019), and night (rho = 0.218, P = 0.036); furthermore, it was associated with lower TAR in the afternoon (rho = -0.275, P = 0.008) and TBR in the evening (rho = -0.235, P = 0.024). Concern about the effect of blood glucose fluctuation on social communication affected the number of scans during the day. Concerns about loneliness and hypoglycemia when alone also influenced the number of nighttime scans. Conclusion: Scan frequency is influenced by psychological factors. Afternoon scans were associated with the highest increase in TIR and decrease in TAR. Evening scans were linked to a reduction in TBR.