Effectiveness of continuous glucose monitoring in maintaining glycaemic control among people with type 1 diabetes mellitus: a systematic review of randomised controlled trials and meta-analysis

The aim of this work was to assess the effectiveness of continuous glucose monitoring (CGM) vs self-monitoring of blood glucose (SMBG) in maintaining glycaemic control among people with type 1 diabetes mellitus. Cochrane Library, PubMed, Embase, CINAHL, Scopus, trial registries and grey literature were searched from 9 June 2011 until 22 December 2020 for RCTs comparing CGM intervention against SMBG control among the non-pregnant individuals with type 1 diabetes mellitus of all ages and both sexes on multiple daily injections or continuous subcutaneous insulin infusion with HbA1c levels, severe hypoglycaemia and diabetic ketoacidosis (DKA) as outcomes. Studies also included any individual or caregiver-led CGM systems. Studies involving GlucoWatch were excluded. Risk of bias was appraised with Cochrane risk of bias tool. Meta-analysis and meta-regression were performed using Review Manager software and R software, respectively. Heterogeneity was evaluated using χ2 and I2 statistics. Overall effects and certainty of evidence were evaluated using Z statistic and GRADE (Grading of Recommendations, Assessment, Development and Evaluation) software. Twenty-two studies, involving 2188 individuals with type 1 diabetes, were identified. Most studies had low risk of bias. Meta-analysis of 21 studies involving 2149 individuals revealed that CGM significantly decreased HbA1c levels compared with SMBG (mean difference −2.46 mmol/mol [−0.23%] [95% CI −3.83, −1.08], Z = 3.50, p=0.0005), with larger effects experienced among higher baseline HbA1c >64 mmol/mol (>8%) individuals (mean difference −4.67 mmol/mol [−0.43%] [95% CI −6.04, −3.30], Z = 6.69, p<0.00001). However, CGM had no influence on the number of severe hypoglycaemia (p=0.13) and DKA events (p=0.88). Certainty of evidence was moderate. CGM is superior to SMBG in improving glycaemic control among individuals with type 1 diabetes in the community, especially in those with uncontrolled glycaemia. Individuals with type 1 diabetes with HbA1c >64 mmol/mol (>8%) are most likely to benefit from CGM. Current findings could not confer a concrete conclusion on the effectiveness of CGM on DKA outcome as DKA incidences were rare. Current evidence is also limited to outpatient settings. Future research should evaluate the accuracy of CGM and the effectiveness of CGM across different age groups and insulin regimens as these remain unclear in this paper. Registration no. CRD42020207042. This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.