MON-560 - The Impact of Continuous Glucose Monitoring (CGM) Usage Patterns on Glycemic Control in Patients with Type 1 Diabetes

Objective
This study aims to assess the impact of different continuous glucose monitoring (CGM) usage patterns on glycemic control in patients with type 1 diabetes mellitus (T1DM). Through a retrospective analysis of T1DM patients regularly attending the endocrinology outpatient clinic of Peking University First Hospital, we explored the relationship between the frequency of CGM use and changes in glycemic indicators, providing evidence for optimizing blood glucose management strategies.
Methods
We conducted a retrospective cohort study including patients diagnosed with T1DM between January 2019 and March 2025 who had completed at least two CGM sessions with complete data. Cases with other diabetes types, missing information, or monitoring intervals shorter than 90 days were excluded. Statistical analysis was performed using SPSS 16.0 software, including the Wilcoxon rank-sum test, McNemar test, and time-series mixed linear regression models.
Results
A total of 34 T1DM patients were included, with 330 valid CGM reports analyzed. The cohort comprised 13 males (38.2%) and 21 females (61.8%), with a mean age of 58.4 ± 12.4 years and a median diabetes duration of 7.0 years (range 4.0–25.0). The median number of CGM sessions was 7.0 (range 3.8–14.0), and the median interval between sessions was 70.1 days (range 27.8–163.0).
The mean time in range (TIR) was 62.3% ± 15.7%, time above range (TAR) was 29.5% ± 17.4%, and time below range (TBR) was 8.2% ± 9.3%. The rate of achieving the TIR target (≥70%) increased by 11.70% (P=0.343), accompanied by a slight increase in TAR and a significant reduction in TBR.
The time-series mixed linear regression model revealed that the baseline TIR averaged 59.91% (p < 0.001), and each additional CGM session increased TIR by 0.50% (p < 0.001). Improvement in TIR was primarily driven by a reduction in TAR. Patients with shorter diabetes duration showed greater improvement in TIR, while gender and age had no significant effect.
Comparative analysis showed that the TIR-improved group (final TIR > initial TIR) had a significant decrease in TAR (median ΔTAR −7.85% vs. +8.15% in the non-improved group, P=0.002), while changes in TBR were not significantly different between groups. Diabetes duration was significantly shorter in the improved group (median 4.5 vs. 16.0 years, P=0.021). No significant differences were observed in CGM usage frequency, age, sex, or monitoring intervals between the two groups.
Conclusion
Increased frequency of CGM monitoring is associated with improved TIR levels in T1DM patients, although this beneficial effect may have an upper limit. Patients with longer disease duration face greater difficulty in achieving glycemic improvement.

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