Continuous Glucose Monitoring in Type 1 Diabetes, Type 2 Diabetes, and Diabetes During Pregnancy: A Systematic Review with Meta-Analysis of Randomized Controlled Trials

Background: Continuous glucose monitoring (real-time CGM [RT-CGM] and retrospective [professional] CGM [non-RT-CGM]) is an emerging tool to assess glucose levels and variability. We performed a meta-analysis of randomized controlled trials (RCTs) to assess the effect of RT/non-RT-CGM on type 1 (T1D), type 2 (T2D), and diabetes in pregnancy (DiP) compared with self-monitoring of blood glucose (BGM). Methods: We searched PubMed/EMBASE/Cochrane Central Register of Controlled Trials until October 2024. The coprimary outcomes were the weighted mean change differences (WMCDs and absolute differences) from baseline in glycated hemoglobin (HbA1c) and in time in range (TIR%), time below range (TBR%), and time above range (TAR%). Results: A total of 64 RCTs were analyzed: (1) RT-CGM/T1D: CGM was superior to BGM for HbA1c reduction (WMCD -0.24, 95% confidence interval [CI]: -0.35; -0.14, I² = 71%), decrease in TBR <70 mg/dL (WMCD -2.41, 95% CI: -3.46; -1.35, I² = 96%), decrease in TBR < 54 mg/dL (WMCD -1.18 95% CI: -1.9; -0.47, I² = 97%), decrease in TAR >180 mg/dL (WMCD -2.99, 95% CI: -5.28; -0.71, I² = 92%), decrease in TAR >250 mg/dL (WMCD -3.99, 95% CI: -5.76; -2.21, I² = 92%), and increase in TIR 70-180 mg/dL (WMCD 5.57, 95% CI: 4.13; 7.01, I² = 84%); (2) RT-CGM/T2D: CGM was superior to BGM for HbA1c reduction (WMCD -0.40, 95% CI: -0.55; -0.24, I² = 52%), decrease in TAR > 180 mg/dL (WMCD -6.32, 95% CI: -9.87; -2.78, I² = 84%), decrease in TAR > 250 mg/dL (WMCD -5.73, 95% CI: -8.96; -2.49, I² = 89%), and increase in TIR 70-180 mg/dL (WMCD 5.46, 95% CI: 2.76; 8.16, I² = 69%); (3) RT-CGM/DiP: CGM was superior to BGM for TIR 63-140 mg/dL (WMCD: 17.77, 95% CI: 4.17; 31.36, I² = 92%). No benefit was shown for HbA1c, TBR < 63 mg/dL, TAR > 140 mg/dL, and most of the maternal and neonatal outcomes of interest; (4) Non-RT CGM: HbA1c significantly decreased with non-RT CGM compared with BGM in T2D (WMCD -0.35, 95% CI: -0.5; -0.2, I² = 19%). Discussion: In T1D and T2D, RT-CGM decreased HbA1c and increased time in target range for glycemia (70-180 mg/dL) while decreasing time spent in hypoglycemia (T1D) and time in hyperglycemia (T1D, T2D).