Search results

The initial search resulted in 8000 articles (ESM Fig. 1). After removal of duplicates, 3994 articles were screened for title and abstract, of which 3971 articles were excluded. Articles were mainly excluded due to incorrect study design (e.g. observational study or no relevant research question) (n=2111). The full texts of 23 studies were assessed, of which 11 were excluded because of incorrect study design (n=5), use of a device other than rtCGM or isCGM (n=4), study duplicate (n=1) or not studying individuals with type 2 diabetes (n=1). Finally, 12 RCTs were included. Corresponding authors of the publications of all 12 RCTs were contacted to obtain any missing data, and the investigators of five RCTs [21,22,23,24,25] provided additional data.

Characteristics of included trials

The 12 RCTs were published between 2008 and 2023 and included a total of 1248 participants. The sample size ranged from 25 to 224 participants (Table 1). Participants (43.3% female) had a mean age of 58.9 years and a mean diabetes duration of 14.7 years. The baseline HbA1c ranged from a mean of 61.1 mmol/mol (7.83%) to 77.9 mmol/mol (9.27%) (Table 1). Eleven trials had a two-arm open-label parallel group design [21,22,23,24,25,26,27,28,29,30,31]. One trial had a three-arm parallel group design [32], including arms with 1 week of CGM use at baseline only (first arm), 1 week of CGM use at both baseline and at the end of the study period after 12 weeks (second arm) and a control arm that did not use CGM (third arm) [32]. We only included data of the intervention arm with CGM use at both the start and study endpoint and control. Eight trials compared rtCGM to SMBG [22, 26,27,28,29,30,31,32] and four trials compared isCGM to SMBG [21, 23,24,25]. No studies compared rtCGM to isCGM. The intervention duration ranged from 10 to 34 weeks (Table 1). Five trials had an extended follow-up period of 24 to 52 weeks [21, 24, 29, 30, 32]. In seven trials, CGM was used continuously [21,22,23,24,25,26, 28], whereas five trials used intermittent wearing of the CGM ranging from two cycles of 2 days to continuous use [27, 29,30,31,32]. As the primary outcome, 10 trials had HbA1c [22,23,24, 26,27,28,29,30,31,32], one trial had TIR [21] and another trial had treatment satisfaction [25]. Four trials included participants on insulin therapy only [22, 23, 25, 28], three trials included participants on oral glucose-lowering medication only [24, 29, 32] and five trials included participants on both insulin and/or oral glucose-lowering medication [21, 26, 27, 30, 31].

Table 1 Characteristics of the RCTs identified Risk of bias

Four trials [21, 22, 24, 28] had an overall low risk of bias, whereas eight trials [23, 25,26,27, 29,30,31,32] had some concerns (ESM Fig. 2). As for the domain of ‘randomisation process’, three trials [25, 29, 30] were graded with some concerns due to lack of information about the randomisation and allocation concealment process. All trials were graded with low risk of bias for the domains ‘deviation from the intended interventions’, ‘missing outcome data’ and ‘measurement of the outcome’. As for the domain of ‘selection of the reported results’, seven trials [23, 25,26,27, 29, 31, 32] were graded with some concerns due to missing trial protocols and statistical analysis plan.

Primary outcome

Results of all included 12 trials [21,22,23,24,25,26,27,28,29,30,31,32] were pooled in the primary meta-analysis. The mean change in HbA1c level was −3.43 mmol/mol (−0.31%; 95% CI −4.75, −2.11, p<0.00001) in favour of the CGM group (Fig. 1). Heterogeneity was low (I2=15%) and we found no evidence of publication bias (ESM Fig. 3; Egger test, p=0.29). Using GRADE criteria, the HbA1c outcome was graded with moderate certainty (Table 2).

Fig. 1