Table 3.

The aims and outcomes of the included studies.

Authors (Year)	Title	Aim of the Study	Exposure or Intervention	Findings
Lu et al. (2021) [40]	Time in range in relation to all-cause and cardiovascular mortality in patients with type 2 diabetes: a prospective cohort study	To study the associations between TIR and all-cause mortality or CVD mortality in patients with T2DM.	Each patient wore a CGM sensor at the first day of hospitalisation, which was kept in place for three days.	There was a negative association between TIR and long-term risks of all-cause and CVD mortality. Increased risks of all-cause and CVD mortality were observed for patients with HbA1c < 6% and ≥8% compared with those with HbA1c levels between 6.0 and 6.9%. TIR was negatively associated with HbA1c levels, the history of CVD, and use of hypertension medicines, aspirin, and statins.
Su, et al. (2018) [41]	Admission glycaemic variability correlates with in-hospital outcomes in diabetic patients with non-ST segment elevation acute coronary syndrome undergoing percutaneous coronary intervention	To assess the relationship among admission GV with in-hospital MACE in patients with T2DM and NSTE-ACS undergoing PCI.	CGM devices were fitted after admission and monitored for 24–72 consecutive hours.	MACE occurred in 48 patients (6.3%) during hospital stay. The higher-MAGE group had higher rates of MACE (9.9% vs. 4.8%, p = 0.009) and all-cause mortality (2.3% vs. 0.4%, p = 0.023) compared with the lower-MAGE group. The rates of new-onset MI (1.9% vs. 1.4%), AHF (3.8% vs. 1.4%), and stroke (1.9% vs. 0.8%) were all higher in the high-MAGE than low-MAGE groups, but the changes were statistically non-significant (all p > 0.05). MAGE compared with HbA1c was a better predictor of in-hospital MACE (AUROC for MAGE = 0.608, 95% CI 0.524–0.692, p = 0.012; and for HbA1c = 0.556, 95% CI 0.475–0.637, p = 0.193).
Mita et al. (2023) [42]	Continuous glucose monitoring-derived time in range and CV are associated with altered tissue characteristics of the carotid artery wall in people with type 2 diabetes	Primary aim: to examine the relationship between TIR and CV at baseline, and changes in IMT and GSM. Secondary aim: to evaluate the association of other GV indices at baseline and HbA1c with changes in IMT and GSM.	Fitting of CGM (data extracted during the middle 8 days of the 14-day lifetime of CGM device) and ultrasound scan for carotid artery.	Over the study period of 104 weeks, IMT increased from 0.759 ± 0.153 mm to 0.773 ± 0.152 mm, p < 0.001. Similarly, thickened-lesion GSM increased from 43.5 ± 19.5 units to 53.9 ± 23.5 units, p < 0.001. However, no significant changes in common carotid artery maximum-IMT were observed (from 1.109 ± 0.442 to 1.116 ± 0.469 mm, p = 0.453). Baseline TIR and glucose CV were significantly associated with the annual change in thickened-lesion GSM. HbA1c was not associated with changes in the mean IMT, mean GSM or thickened-lesion GSM after adjusting for multiple testing.
Lu et al. (2021) [43]	Association of HbA1c with all-cause mortality across varying degrees of glycaemic variability in type 2 diabetes	To examine the relationships between HbA1c levels and all-cause mortality across different degrees of GV in patients with T2DM.	Each patient wore a CGM sensor at the first day of hospitalisation, which was kept in place for three days.	Amongst patients in the lowest and middle tertiles of glucose CV, an HbA1c ≥ 8.0% was associated with 136% (HR 2.36, 95% CI 1.46–3.81) and 92% (HR 1.92, 95% CI 1.22–3.03) increased risk of all-cause mortality, respectively. Each 10% decrease in TIR was associated with a 12% (HR 1.12, 95% CI 1.04–1.20) increase in the risk of all-cause mortality, and every 10% increase in TAR7.8, TAR10, and TAR13.9 was associated with an 11% (HR 1.11, 95% CI 1.04–1.19), 11% (HR 1.11, 95% CI 1.04–1.18), and 14% (HR 1.14, 95% CI 1.04–1.25) increase in the risk of all-cause mortality, respectively, among the patients in the highest tertile of glucose CV.
Andersen et al. (2021) [44]	Associations of hypoglycaemia, glycaemic variability, and risk of cardiac arrhythmias in insulin-treated patients with type 2 diabetes: a prospective, observational study	To examine the association between arrhythmia and glucose fluctuations and episodes of hypoglycaemia.	In months 1 and 12, patients wore a CGM sensor over four periods of six days; plus, one 6-day period of monitoring per month during the 10 months in between. CGM was undertaken for the total period of 108 days at maximum.	Time in hypoglycaemia was longer at night compared to daytime (median [IQR], 0.7% [0.7–2.7%] vs. 0.4% [0.2–0.8%] respectively). The severity of hypoglycaemia was slightly higher during daytime. Asymptomatic cardiac arrhythmias occurred more frequently at night compared to daytime (IRR 4.22 [3.48–5.15]). Incidence rate of arrhythmias had positive associations with CV and SD during night, but negative associations were observed during day. GV is an independent predictor of cardiac arrhythmias in patients with T2DM treated with insulin.
Ajjan et al. (2023) [45]	Multicentre randomised trial of intermittently scanned continuous glucose monitoring versus self-monitoring of blood glucose in individuals with type 2 diabetes and recent-onset acute myocardial infarction: results of the LIBERATES trial	To examine the impact of in-hospital use of isCGM in optimising glycaemic control and improving patient-related outcomes in persons with T2DM and recent MI.	In the intervention arm, participants wore isCGM sensors for 90 consecutive days and asked to change their sensors every 14 days. Patients in the control arm wore three sensors in total, two during the first month (14 days monitoring for each) and the third one on days 76–90.	In the intervention group, compared with the control (SMBG) group, TIR (days 76–90) increased by 17 min/day (95% credible interval −105 to +153 min/day) with 59% probability of benefit. When criteria were relaxed to include glucose coverage of 65% per day, the difference between study arms increased to 28 min in favour of the isCGM group. The isCGM group experienced lower hypoglycaemic exposure at days 76–90 (−80 min/day; 95% CI −118–−43) and days 16–30 (−28 min/day; 95% CI −92–2). Compared to baseline, both study arms showed similar reductions in HbA1c levels at 3 months (7 mmol/mol). Combined glycaemic emergencies and mortality occurred in four is-GM and seven SMBG participants.

AHF, acute heart failure; AUROC, area under the receiver operating characteristic curve; CGM, continuous glucose monitoring; CI, confidence interval; CVD, cardiovascular disease; GSM, grey-scale median; GV, glycaemic variability; HR, hazard ratio; IMT, intima–media thickness; IRR, incident rate ratio; IQR, interquartile range; isCGM, intermittently scanned continuous glucose monitoring; MACE, major adverse cardiac events; MI, myocardial infarction; NSTE-ACS, non-ST segment elevation acute coronary syndrome; PCI, percutaneous coronary intervention; SMBG, self-monitoring of blood glucose; T2DM, type 2 diabetes mellitus; TAR7.8, TAR > 7.8 mmol/L or >140 mg/dL; TAR10, TAR > 10 mmol/L or >180 mg/dL; TAR13.9, TAR > 13.9 mmol/L or >250 mg/dL; TIR, Time in Range.