While they have been in existence for many years now, continuous glucose monitoring (CGM) systems still aren’t used as widely among people with diabetes as traditional (finger-stick) glucose meters to check blood glucose levels. In part, that’s because finger-stick devices are much simpler and cheaper, so CGM systems are usually reserved for people who are likely to see a significant improvement in their health from using them — especially people with type 1 diabetes. CGM systems also require wearing a sensor that’s inserted into your skin, which needs to be changed according to a recommended schedule, and keeping an electronic receiver device nearby to record and display your glucose levels.
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Because of the effort they typically require, some people with diabetes may find it difficult to stick to using a CGM system all the time once they have it. This limits the potential benefits of CGM, including knowing when your glucose level is dropping or rising so that you can take corrective action. So with any CGM system, it’s important to study how people actually use it, and how the corrective action they take — or don’t take — contributes to their overall blood glucose levels. Two recent studies, published in the journal JAMA, looked at real-world use of CGM in two groups considered at high risk for out-of-range blood glucose levels: adolescents and young adults, and older adults, with type 1.
CGM in young people with type 1
The first study, which looked at adolescents and young adults, included 153 people with type 1 between the ages of 14 and 24. Participants were randomly assigned to use either a CGM system or a traditional glucose meter for six months. At the beginning of the study, participants’ HbA1c level (a measure of long-term blood glucose control) ranged from 7.5% to 10.9%, with an average of 8.9%.
After 6 months, average HbA1c in the CGM group had fallen from 8.9% to 8.5%, while it remained the same at 8.9% in the regular-meter group. This benefit occurred even though only 68% of participants in the CGM group used their devices at least five days per week during the sixth month of the study, as noted in a Medpage Today article on the new studies. Members of the CGM group also spent a greater amount of time within their target glucose range (70 to 180 mg/dl): 43% of the time, versus 35% in the regular-meter group. Three members of the CGM group developed severe hypoglycemia (low blood glucose) during the study, compared with two members of the regular-meter group.
Even though they didn’t use their CGM systems as often as researchers would have liked, members of the CGM group reported higher levels of satisfaction with their glucose monitoring than the regular-meter group in a survey at the end of the study period.
CGM in older adults with type 1
The second study, which looked at adults age 60 and older, included 203 people with type 1. Just like in the first study, participants were randomly assigned to use either a CGM system or a traditional glucose meter for six months. But in this study, the main outcome that researchers were interested in was the amount of time experiencing hypoglycemia, defined as glucose below 70 mg/dl.
In this study, 83% of members of the CGM group used their devices at least six days a week during the sixth month — a much higher use rate than in the first study. In CGM users, the amount of time with glucose below 70 mg/dl fell from 5.1% (73 minutes per day) at the beginning of the study to 2.7% (39 minutes per day) during the study period. In contrast, members of the regular-meter group saw a slight increase in hypoglycemia, from 4.7% of the time (68 minutes per day) to 4.9% (70 minutes per day).
One member of the CGM group developed severe hypoglycemia during the study, compared with 10 members of the regular-meter group. When it came to other adverse events, five members of the CGM group had a bone fracture during the study, compared with only one member of the regular-meter group, while four members of the CGM group experienced a fall compared with three in the regular-meter group. Six members of the CGM group had to visit an emergency room for any reason, compared with eight members of the regular-meter group. Since all of these numbers were low, random chance could account for some or possibly all of these differences.
Overall, these two studies show that CGM may be beneficial in two different groups of people with type 1 diabetes at risk for poor glucose control. One major limitation of both studies was the short study period of six months, which isn’t long enough to follow most long-term risks or benefits that may be associated with CGM. More studies are needed to gain a greater understanding of CGM’s potential in these groups.
Want to learn more about CGM? Read “CGM for Diabetes” and “Sensing the Big Picture With Continuous Glucose Monitoring” and “Continuous Glucose Monitoring Updates.”