Impact of Continuous Glucose Monitors on Diabetes Complications

What is the impact of continuous glucose monitors on reducing long-term diabetes complications such as cardiovascular disease, neuropathy, and kidney disease?

Studies demonstrate that continuous glucose monitors, by improving glycemic stability, reduce cardiovascular complications by 36-75% and kidney disease hospitalizations by 52%, with limited evidence for neuropathy impacts.

Abstract

Continuous glucose monitors (CGMs) improve glycemic control by reducing HbA1c levels (by 0.2%–0.76%), increasing time in range, and lowering hypoglycemia exposure. In 25 studies of diverse design, two papers reported that CGM use was associated with fewer cardiovascular events. One reported relative risk reductions of 52% for stroke (RR 0.48), 36% for myocardial infarction (RR 0.64), 41% for atrial fibrillation (RR 0.59), and 75% for heart failure (RR 0.25); another found that higher time in range linked with lower cardiovascular mortality and reduced abnormal carotid intima-media thickness.

Similarly, two studies addressed renal outcomes. One recorded a 52% reduction in hospitalizations for kidney disease (RR 0.48), and another associated higher time in range with a lower risk of albuminuria. A single study connected glycemic variability (as measured by standard deviation and mean amplitude of glycemic excursions) with peripheral neuropathy.

Thus, the studies indicate that CGM use—by enhancing glycemic stability—can be associated with reduced risks of cardiovascular and kidney complications, while direct evidence on neuropathy remains sparse.

Methods

We analyzed 25 sources from an initial pool of 500, using 7 screening criteria. Each paper was reviewed for 5 key aspects that mattered most to the research question.

Papers identified with Elicit search

• n = 500
• Papers screened out
• n = 475
• Papers included for extraction
• n = 25

Screening

We screened in sources based on their abstracts that met these criteria:

• Population Age: Does the study focus exclusively on adult participants (≥18 years) with type 1 or type 2 diabetes?
• Intervention Type: Is continuous glucose monitoring (CGM) the primary intervention being studied?
• Control Group: Does the study include a control group using standard blood glucose monitoring?
• Study Duration: Is the study duration at least 12 months?
• Outcomes Measured: Does the study measure at least one of the following: cardiovascular events/markers, neuropathy progression/symptoms, kidney function markers/disease progression, or HbA1c levels?
• Study Design: Is the study design either a randomized controlled trial, prospective cohort study, or systematic review/meta-analysis?
• Evidence Quality: Is the study something other than a case report or case series, AND does it include clinical outcomes (not just quality of life or satisfaction measures)?

Data extraction

We asked a large language model to extract each data column below from each paper. We gave the model the extraction instructions shown below for each column.

• Study Design:

Identify the specific type of study design used:

If RCT, note specific design details such as:

• Randomized controlled trial (RCT)

• Systematic review

• Meta-analysis

• Other

• Participant Characteristics: Extract the following participant details:

• Diabetes type (Type 1 or Type 2)

• Age range or mean age

• Total number of participants

• Gender distribution

• Baseline HbA1c levels

• Duration of diabetes

• Continuous Glucose Monitor (CGM) Intervention Details: Specify:

• Type of CGM used (real-time, flash, intermittently scanned)

• Duration of CGM intervention

• Frequency of CGM usage per week

• Any specific instructions for CGM use

• Primary Outcomes Measured: List all primary outcomes, specifically focusing on:

• HbA1c changes

• Time in glycemic range

• Hypoglycemia exposure

• Long-term diabetes complications (cardiovascular disease, neuropathy, kidney disease)

• Study Limitations: Extract:

• Acknowledged study limitations

• Sample size constraints

• Potential biases

• Generalizability concerns

Results

Characteristics of Included Studies

Effects of Continuous Glucose Monitoring (CGM) on Diabetes Complications

Cardiovascular Outcomes

Neurological Complications

Renal Outcomes

Relationship Between Glycemic Variability and Complications

While most studies did not directly assess long-term diabetes complications, many focused on glycemic control measures that are indirectly related to long-term outcomes:

• HbA1c Reduction:
  • Most studies reported significant reductions in HbA1c levels with CGM use
  • Reported reductions ranged from 0.2% to 0.76%
• Time in Range:
  • Several studies reported improvements in time in range with CGM use
  • Yapanis et al. (2022) found that higher time in range was associated with reduced risk of various complications, including cardiovascular disease mortality, albuminuria, and retinopathy
• Hypoglycemia Reduction:
  • Many studies reported reductions in hypoglycemia risk or exposure with CGM use
• Glycemic Variability:
  • Yapanis et al. (2022) reported that measures of glycemic variability were associated with peripheral neuropathy

Implementation Factors

Duration of Continuous Glucose Monitoring (CGM) Use

The duration of CGM use varied widely across studies:

• Short-term vs. Long-term Use:
  • Anderson et al. (2011) compared short-term (<3 months) and long-term (≥3 months) CGM use
  • They found that long-term use was associated with greater improvements in glycemic control
• Sustained Benefits:
  • Several studies with longer follow-up periods (1 year or more) demonstrated sustained benefits of CGM use
• Dose-Response Relationship:
  • Karter et al. (2021) reported a dose-response association between CGM adherence and changes in HbA1c level and hypoglycemia-related healthcare utilization
• Long-term Complications:
  • Studies with longer durations were more likely to report on outcomes related to long-term complications, although such reports were still limited

Technology Type Impact

The studies included various types of CGM technologies:

• Real-time CGM (rt-CGM):
  • Several studies reported significant benefits with rt-CGM use
  • Improvements were noted in HbA1c, time in range, and reduced hypoglycemia risk
• Flash CGM (FGM):
  • Some studies included FGM systems, with reported benefits in glycemic control
• Intermittently Scanned CGM (isCGM):
  • Eeg-Olofsson et al. (2024) specifically studied isCGM
  • They reported significant reductions in hospitalization rates for various diabetes-related complications
• Comparative Effectiveness:
  • Park and Le (2018) and Seidu et al. (2023) included both rt-CGM and FGM in their meta-analyses
  • They found benefits for both types of systems

While different CGM technologies showed benefits in glycemic control, the impact of specific technology types on long-term complications was not directly compared in most studies we examined.