For a while now, the Juvenile Diabetes Research Foundation (JDRF) has been conducting clinical trials on the effectiveness of continuous glucose monitoring (CGM) for people with type 1 diabetes. Last year, they issued their first two reports on their findings, showing that CGMs can improve control even for people who already have A1c’s below 7%. That information has already had a powerful impact: It’s convinced a number of large health insurers (including Aetna, Cigna, Kaiser Permanente, United Healthcare, and Wellpoint) to cover CGMs for type 1s, and it’s led to the inclusion of CGMs in national standards of care for type 1 diabetes.
Now the JDRF has released their third and fourth reports, and they even more strongly support the use of CGMs. According to their studies, which were recently published online by the journal Diabetes Care, the regular use of a CGM is a more important contributor to good control of blood sugar than age or background. Not only that, but use of a CGM also actually reduces the incidence of hypoglycemia, despite the tight control that it allows.
The Diabetes Control and Complications Trial (DCCT) previously demonstrated that when blood sugar is intensively controlled, complications are reduced. The progression of eye disease, for example, drops 40 percent with every 10 percent decrease in A1c. Unfortunately, however, intense control leaves very little wiggle room when blood sugar drops even slightly. During the DCCT, for example, 62 hypoglycemic events occurred during a six-month period. But the JDRF study indicates that even with very tight control, use of a CGM over an extended period of time can reduce the number of hypoglycemic events. During the second six months of the JDRF trial, only seven hypoglycemic events occurred, even though the average A1c of JDRF participants was lower than that of DCCT participants: 6.8% compared to 7.1%.
Continuous glucose monitors consist of a disposable glucose sensor placed under the skin, a link from the sensor to a transmitter, and an electronic receiver that displays the information. CGMs allow patients to monitor their glucose levels “continuously,” or at least every few minutes. Consequently, when they see a blood glucose number that requires correction, they also know if they’re hitting that number on the way up or on the way down. That information makes it infinitely easier to know what kind of a correction to make. One issue with CGMs is that the sensor measures glucose in the interstitial fluid, not the blood. Therefore, the system must be repeatedly calibrated with data from blood glucose fingersticks. There’s also a five-minute lag before a blood glucose level can be accurately derived from interstitial fluid.
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Diabetes Care abstract