Effectiveness of continuous glucose monitoring in patient management of Type 2 Diabetes Mellitus: an umbrella review of systematic reviews from 2011 to 2024

Abstract

Background: Continuous glucose monitoring (CGM) is increasingly popular for managing Type 2 Diabetes Mellitus (T2DM). Many systematic reviews have reported on CGM's effectiveness, but with heterogeneous methodologies and objectives. We aim to conduct an umbrella review (UR) to consolidate a most contemporaneous and comprehensive evidence base comparing CGM with self-monitoring of blood glucose or usual care (SMBG/UC).

Methods: Ovid MEDLINE, Ovid Embase, Cochrane Database of Systematic Reviews, CINAHL, Epistemonikos, SCOPUS, Web of Science and PubMed were searched from their dates of inception to 28th June 2024. Systematic reviews (SR) with or without meta-analyses comparing the use of CGM with SMBG or usual care (UC) for T2DM management in patients treated with or without insulin were included. Narrative synthesis of HbA1c, glycemic variability metrics and other physical measurements were done. Corrected covered area (CCA) was calculated to assess suitability of meta-meta-analysis.

Results: 31 SRs were included in this UR. There was high overlap within meta-analyses of HbA1c, time-in-range (TIR), time-above-range (TAR) and time-below-range (TBR). A primary study-level meta-analysis demonstrated that compared to SMBG/UC, CGM was associated with significantly greater HbA1c decrease (n = 11,494, MD = -0.40% [95% CI: -0.54 to -0.25]), TIR increase (n = 1452, MD = 6.00% [95%CI: 3.13 to 8.88]) and TAR decrease (n = 1113, MD = -4.33% [95%CI: -8.37 to -0.28]).These findings were invariant with CGM modality, study funding, pre-existing insulin treatment and risk-of-bias. Meta-analysis of patient reported outcome measures (PROMs) demonstrated insignificant differences in PROMs with CGM use compared to SMBG/UC.

Conclusion: CGM could lead to better clinical outcomes than SMBG/UC and was of moderate evidence certainty (GRADE), while its effect on PROMs remains inconclusive. We recommend the introduction of CGM into standard care alongside SMBG for T2DM and further research exploring patient experience and acceptability of CGM use.

Keywords: Chronic Disease Management; Continuous Glucose Monitoring; Meta-Analysis; Systematic Review; Type 2 Diabetes; Umbrella Review.

Fig. 1

a-b Forest plot for meta-analysis of primary studies comparing CGM with SMBG from 2008 to 2022 by pooling the mean difference in pre-post HbA1c (%) change between CGM and SMBG users (a) across all studies, subgrouped by study type and (b) across RCTs only subgrouped by CGM modality. Correlation coefficient for imputation set at 0.30. CGM significantly associated with greater HbA1c decrease over SMBG (a) (MD = −0.40, 95% CI: −0.54 to −0.25) (b) (MD = −0.42, 95% CI: −0.60 to −0.24)

Fig. 2

a-c Forest plot for meta-analysis of primary studies comparing CGM with SMBG from 2009 to 2023 by pooling the mean difference in pre-post change of (a) TIR, (b) TAR and (c) TBR between CGM and SMBG/UC participants. CGM significantly associated with greater TIR increase (MD= 6.00 [95%CI: 3.13 to 8.88]) and greater TAR decrease (MD= −4.33 [95%CI: −8.37 to −0.28]), and insignificantly associated with greater TBR decrease (MD= −0.33 [95%CI: −0.75 to 0.09]) over SMBG/UC participants. TIR and TBR were invariant with CGM modality (p = 0.87, p = 0.54) but not TAR (p = 0.03)

Fig. 3

Forest plot for meta-analysis of primary studies comparing CGM with SMBG from 2014 to 2023 by pooling the standardized mean difference of pre-post change in patient reported outcome measures subgrouped by domains, specifically satisfaction, distress, adherence, self-management, patient education, quality-of-life and empowerment. None of the domains demonstrated a statistically significant effect size