Continuous glucose monitoring (CGM) is linked to better blood glucose control and fewer emergency room visits for hypoglycemia (low blood glucose) in people with type 2 diabetes, according to a new study published in the journal JAMA.
CGM systems involve a sensor that detects glucose levels under your skin at regular intervals, and automatically records these glucose levels by communicating with software on another device, such as a smartphone or another portable screen-based device. When glucose levels start to drop, the system can sound an alarm so that you can take action — such as by consuming glucose in some form by mouth — and avoid dangerously low blood glucose. Many CGM systems now can work in tandem with an insulin pump in what is often called a hybrid closed-loop system, or an artificial pancreas. But for people with type 2 diabetes, wearing a CGM system by itself — without an insulin pump — can have value if you take insulin injections.
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For the latest study, researchers looked at 41,753 people with diabetes who received care in a healthcare system in Northern California. All of them took insulin for their diabetes, regardless of whether they had type 1 (5,673 participants) or type 2 (36,080 participants). None of the participants had used a CGM system before enrolling in the study. Participants had a number of measurements taken during the 12 months before, and the 12 months after, the beginning of the study, including A1C (a measure of long-term blood glucose control), hypoglycemia requiring emergency attention or hospitalization, and emergency room visits or hospitalization for any reason.
Since this wasn’t a randomized study — it simply looked at what happened in people who did or didn’t start using a CGM system — there were major differences between participants who started with CGM and those who didn’t. Among the 3,806 participants who started CGM, 91% had type 1 diabetes, while among the 37,947 participants who didn’t start CGM, 94% had type 2. A1C at the beginning of the study was lower among those who started CGM, but this group also had more incidents of hypoglycemia and hyperglycemia (high blood glucose).
CGM use linked to better blood glucose control, less hypoglycemia
Those in the CGM group saw their average A1C level drop from 8.17% to 7.76%, while the group that didn’t start CGM saw a drop only from 8.28% to 8.19%. The proportion of people who experienced hypoglycemia dropped from 5.1% to 3.0% in the CGM group, while this proportion actually rose in the non-CGM group from 1.9% to 2.3%. There were also statistically significant improvements in the CGM group for the number of participants with an A1C level below 7%, 8%, or 9%. There were not, however, any significant improvements seen in rates of hyperglycemia, emergency department visits for any reason, or hospitalizations for any reason.
The researchers concluded that starting CGM may result in fewer episodes of hypoglycemia, as well as better overall blood glucose control. But more studies are needed of CGM that follow a randomized design, to eliminate the possibility — a strong likelihood, in this study — that outcomes are affected by the type of person who chooses to use a CGM system.