Use of continuous glucose monitoring (CGM) offers significant benefits for both youth and older adults with type 1 diabetes, new research suggests. 

The findings come from two studies.

• One study — demonstrating improvements in glycemic control with CGM at 26 weeks in individuals aged 14 to 24 years — was published June 16 in JAMA. Further data showing these improvements were maintained at 1 year were presented in a poster at the virtual American Diabetes Association (ADA) 80th Scientific Sessions.

• The other study, which showed reductions in hypoglycemia with CGM use in adults aged 60 and older with type 1 diabetes, was also published June 16 in JAMA.

"CGM has become a vital tool for glycemic management in individuals with type 1 diabetes," and these new data further support its use, say Shivani Agarwal, MD, Albert Einstein College of Medicine, New York City, and Anne R. Cappola, MD, of the University of Pennsylvania, Philadelphia, in an accompanying editorial. 

But CGM use currently remains lower than expected, they stress.

The greatest use of this technology is in people younger than 13 years and adults aged 26-50 years rather than the two highest-risk populations who could uniquely benefit from it: adolescents/young adults and older adults.

The younger group is at increased risk because of the tumultuous social, biologic, and healthcare changes that occur during that phase of their lives, which impedes their ability to self-manage their diabetes.

And older adults are at increased risk for hypoglycemic unawareness due to cognitive impairment, or autonomic neuropathy if they've had type 1 diabetes for many years. 

The new study in older adults does show that they were more likely to consistently wear CGMs than teens/young adults, the editorialists add.

"High rates of consistent CGM wear bodes well for acceptability of more advanced CGM technologies and future artificial pancreas systems in older adults, which could have profound effects on glycemic control," they observe.

However, there remain many barriers to access for all age groups, they stress.

In Teens, Young Adults, Glycemic Benefits at 26 Weeks and 1 Year

The youth study involved 153 individuals with an A1c of 7.5% to less than 11.0% and insulin pump or multiple daily injection use.

The teens and young adults were randomized to using the Dexcom G5 CGM, which required two daily fingerstick calibrations (n = 74) or performing four fingerstick measurements per day without CGM (n = 79). At 26 weeks, 71 participants in each group completed a visit. 

Device use in the CGM group dropped from 82% wearing it for at least 5 days per week initially to just 68% by week 26, Lori M. Laffel, MD, chief of the pediatric, adolescent, and young adult section at the Joslin Diabetes Center, Boston, Massachusetts, and colleagues report in their JAMA article.

Nonetheless, A1c dropped from 8.9% at baseline to 8.5% at 26 weeks in the CGM group, while it remained at 8.9% in the blood glucose monitoring group, a significant between-group difference (P = .01).

The mean percentage of time spent in the target glucose range of 70 to 180 mg/dL was 37% (9.0 hours/day) at baseline and 43% (10.3 hours/day) during follow-up in the CGM group. In the control group, these two periods remained essentially the same: 36% (8.7 hours/day) at baseline and 35% (8.3 hours/day) during follow-up (P < .001, adjusted between CGM and control group difference).

Severe hypoglycemic events occurred in 4% of the CGM group and 3% of the controls, while diabetic ketoacidosis occurred in 4% and 1%, respectively. Participants in the CGM group reported significantly higher glucose monitoring satisfaction at 26 weeks (P = .003).

Results were similar for youth wearing insulin pumps and those taking multiple daily insulin injections.

In the update presented at ADA by Kellee M. Miller, PhD, project director at Jaeb Center for Health Research, Tampa, Florida, A1c in the CGM group had improved to 8.3% at 1 year (P < .001 vs baseline), while time in range had dropped slightly from the 26-week point (43%) to 41% (P = .3 vs baseline).

Mean percent time spent with glucose levels below 70 mg/dL was reduced from 3.4% (49 min/day) at baseline to 1.1% (16 min/day) at 12 months.

Agarwal and Cappola note in their editorial that the attrition in use of the devices among the young people seen in the study may be lessened with newer models of CGM devices that don't require fingerstick calibration.

Among Older Adults, CGM Reduces Hypoglycemia Risk

The older adults trial enrolled 203 adults aged 60 years and older with type 1 diabetes from 22 US endocrinology practices, with 102 randomized to CGM and 100 to 4-times daily fingersticks.

Device use was much higher than among the younger group, with 89% of the older individuals wearing it 5 or more days per week and 81% wearing it continuously.

The median percentage of time with glucose levels below 70 mg/dL dropped from 5.1% (73 min/day) at baseline to 2.7% (39 min/day) at 26 weeks, compared with almost no change in the controls, from 4.7% to 4.9%. 

The difference between groups was significant (P < .001), corresponding to a reduction of 27 min/day, Richard E. Pratley, MD, of the Translational Research Institute for Metabolism and Diabetes, Orlando, Florida, and colleagues report in JAMA.

 Time spent in target blood glucose range of 70-180 mg/dL was 8.8% higher (2.1 hours/day) in the CGM versus the blood glucose monitoring group (P < .001).

Severe hypoglycemia occurred in one CGM group participant and 10 controls. One participant in the CGM group experience diabetic ketoacidosis, but it wasn't related to device use.

A 1-year update was reported by Miller at the Advanced Technologies & Treatments for Diabetes (ATTD) conference in February 2020.

The reduction in hypoglycemia was maintained at 1 year in the CGM group, with 2.8% of time spent below 70 mg/dL (P < .001 vs baseline).

Similarly, median time spent below 54 mg/dL also dropped significantly from 1.9% to 0.4% (P < .001). Time in range was also higher among the CGM group at 1 year (64% vs 56%; P < .001). 

And CGM use remained high, with 85% using the sensor at least 6 days per week at both 6 and 12 months. As with the youth, similar benefits were seen in both insulin pump and multiple daily injection users.

Agarwal and Cappola observe that the reduction in time spent in the severe hypoglycemic range "has healthcare use, mortality, morbidity, and economic benefits" for this older age group.

A New Outlook, but Significant Barriers to Use

"With CGM innovation happening at a rapid pace and the imminent commercial release of artificial pancreas systems, CGM offers a new outlook for patients with type 1 diabetes and for the clinicians and communities caring for them," the editorialists emphasize. 

But there are financial barriers to access in the United States, including strict eligibility criteria set by insurers, and Medicare and Medicaid, requiring that the patient perform 4 daily fingerstick blood glucose checks. And state coverage for CGM varies widely.

Such requirements may therefore contribute to racial/ethnic and age disparities in use, say Agarwal and Cappola.

Other factors affecting access include shortages of endocrinologists with expertise to manage CGM data and lack of training and support for primary care clinicians to deal with CGMs, they add. 

"More effort is needed to overcome current barriers and provide better access to this beneficial technology," they conclude.

JAMA. 2020;323:2384-2385, 2388-2396, 2397-2406.
Abstract 1,

Abstract 2,


"The advent of continuous glucose monitoring (CGM) technology has revolutionized outpatient diabetes care in the past decade. A CGM device consists of a sensor that continuously measures subcutaneous glucose and sends data wirelessly to a display device through a transmitter. CGM offers real-time blood glucose monitoring (BGM) with alerts for trends in blood glucose levels and decreases the need for fingerstick glucose monitoring for people with diabetes. Studies of CGM have shown improvement in glycemic control in adults and children with type 1 diabetes and equivalence to glucometers for self-monitoring of blood glucose.
1-3 Coupled with recent advances in CGM technology to improve accuracy and ease of use, CGM has become a vital tool for glycemic management in individuals with type 1 diabetes."


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ADA 2020 Scientific Sessions. Presented June 13, 2020. Abstracts 898-P


ATTD 2020. Presented February 20, 2020.