Continuous glucose monitoring (CGM) allows people with diabetes to check their blood glucose levels in real time throughout the day. A common CGM system includes a small disposable sensor, a wireless transmitter, and a receiver or compatible smart device. Patients can track their values over time using an app on their smartphone, which may lead to better blood glucose control compared with using a blood glucose meter.
CGM is known to benefit adults with type 1 diabetes, but it hasn't been well studied in those with type 2 diabetes who use insulin. A recent randomized clinical trial has now shown that CGM can improve glucose control in type 2 diabetes patients taking multiple daily injections of insulin. Results of the study were published in Annals of Internal Medicine.
This trial—the DIAMOND (Multiple Daily Injections and Continuous Glucose Monitoring in Diabetes) Study—involved 158 adults with type 2 diabetes from 25 endocrinology practices in North America. Participants were taking multiple daily injections of insulin and had hemoglobin A1c (HbA1c) levels between 7.5% and 9.9% (mean 8.5%). Half of the participants were assigned a CGM system and the other half were told to monitor their blood glucose at least four times a day with an at-home glucose meter.
After 24 weeks, mean HbA1c levels decreased from a baseline of 8.5% to 7.7% in the CGM group and to 8% in the self-monitoring group—a modest but statistically significant reduction. Notably, 52% of participants in the CGM group achieved a relative HbA1c level reduction of at least 10%, compared with 32% in the self-monitoring group who achieved such a reduction. The groups did not differ meaningfully in CGM-measured hypoglycemia or quality-of-life outcomes.
"Because few insulin-treated patients with type 2 diabetes currently use CGM, these results support an additional management method that may benefit these patients," the DIAMOND Study authors concluded.
Lead investigator Roy W. Beck, MD, PhD
In this interview, lead investigator Roy W. Beck, MD, PhD, Executive Director of the Jaeb Center for Health Research in Tampa, FL, discusses the results of this trial, why it was begun, and what it means for patients with type 2 diabetes who use insulin.
MDLinx: Why did you decide to study CGM for patients with type 2 diabetes?
Dr. Beck: Many studies have shown the benefits of CGM in patients with type 1 diabetes, but prior to this study, we knew very little about CGM use in patients with type 2 diabetes using insulin. Dr. Robert Vigersky reported one study of CGM in type 2 diabetes, but it did not focus solely on patients using insulin, was not designed for CGM to be used daily, and was only 12 weeks. Other than that study, there had been very little information about real-time CGM, which shows the glucose readings and has alarms for these types of patients.
With so little information prior to the study, it was really unknown whether (1) patients with type 2 diabetes using insulin would find CGM useful and use it regularly, and (2) if used regularly, whether it would improve glycemic control. So, this study was needed to determine if the benefits seen with CGM in patients with type 1 diabetes would also be seen in patients with type 2 diabetes using insulin.
MDLinx: What are the advantages of CGM vs SMBG? What are the disadvantages?
Dr. Beck: CGM provides a glucose value every five minutes—so 288 measurements per day. Typically, a patient with type 2 diabetes using multiple daily insulin injections might use a blood glucose meter three to six times a day. So CGM provides far more information than self-monitoring to determine optimal insulin dosing both in real-time as well as retrospectively, by viewing patterns of glucose levels over time.
MDLinx: Were you surprised that patients on CGM had only a modest (less than 1%) reduction in HbA1c levels? Also, what about quality-of-life measures?
Dr. Beck: A 1% reduction in HbA1c is a large reduction for an individual patient, and in the study context is a very large reduction when it is a mean reduction across the entire treatment group.
The most relevant questionnaire utilized in the study was the CGM Satisfaction Survey. The scores on this survey were incredibly high, indicating a very high level of satisfaction with CGM, and when the individual questionnaire items were reviewed, it was apparent that these patients really liked CGM and felt that there was substantial benefit to using it.
So, in addition to improving glucose control, CGM had considerable benefit in how these participants approached and thought about their diabetes.
MDLinx: Do you think CGM could be used by nearly all patients with type 2 diabetes, or reserved only for particular subgroups of these patients?
Dr. Beck: The DIAMOND Study included only patients with type 2 diabetes using multiple daily injections of insulin. I believe that all such patients can benefit from using CGM. We don't know how much patients using only long-acting insulin or not using insulin would benefit from CGM.
MDLinx: What barriers impede more widespread use of CGM for patients with type 2 diabetes?
Dr. Beck: Assuming we are talking about CGM for patients with type 2 diabetes using multiple daily injections of insulin, I think the main barriers are patient awareness that CGM exists, insurance coverage, and lack of health care provider experience using CGM for patients with type 2 diabetes.
MDLinx: What's next in this line of investigation?
Dr. Beck: The next natural study to conduct is assessing the benefit of CGM in patients with type 2 diabetes who are using only one injection of long-acting insulin a day. The Jaeb Center is collaborating with Dexcom on such a study, which will start before the end of the year.
About Dr. Beck: Roy W. Beck, MD, PhD, is a physician, an epidemiologist, and the Executive Director of the Jaeb Center for Health Research, a nonprofit company in Tampa, FL, that coordinates multi-center clinical trials.
This study was funded by Dexcom, a manufacturer of CGM systems for diabetes management, which were used in this trial.