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Closed-Loop Therapy a Success in Type 1 Diabetes

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Closed-Loop Therapy a Success in Type 1 Diabetes

For older people with type 1 diabetes, closed-loop insulin pump therapy is linked to more consistent blood sugar control than sensor-augmented therapy, indicates a study just published in the journal Diabetes Care.

What is closed-loop insulin pump therapy? Sometimes described as an artificial pancreas, it connects an insulin pump to a continuous glucose monitor (CGM) to adjust the user’s insulin by utilizing an algorithm that independently increases and decreases insulin delivery in response to real-time sensor glucose levels. On the other hand, sensor-augmented insulin pumps communicate with a CGM system but require the user to make manual adjustments and inputs. Sensor-augmented therapy is referred to as “open-loop” system.

The research team, which was led by Sybil A. McAuley, PhD, of the University of Melbourne in Australia, enlisted 30 people who were aged 60 and above and who had been diagnosed with type 1 diabetes for at least 10 years (the median diabetes duration was 38 years). Nearly two-thirds were women, the average age was 67, and they all had an HbA1c (A1C) reading of 10.5% or lower. All participatnt had previously used an insulin pump.

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After an initial break-in period, the researchers collected data from the subjects for two weeks using an open-loop system. After the two weeks, the patients were randomly assigned to use either an open-loop or a closed-loop system for four months. After the four months, they traded places: the open-loop group switched to a closed-loop system, and vice versa. The closed-loop system the researchers used was the MiniMed 670G manufactured by the medical device company Medtronic. This system, designed for people with diabetes age 7 and above, adjusts insulin levels every five minutes (the MiniMed 670G has since been discontinued and replaced with a newer device).

The researchers used a variety of metrics to evaluate the two systems, although the one that most interested them was what’s known as “time in range.” According to the manufacturer of the MiniMed 670G, time in range is “a relatively new term” that “describes the percentage of time the blood glucose levels stay within a pre-determined range for people with diabetes. Time in range provides a more accurate picture of blood glucose over a period of time.”

Closed-loop insulin delivery linked to better glucose control

After the eight-month trial, the researchers reported, “Closed-loop insulin delivery provided significantly better glucose control than did sensor-augmented pump therapy.” The time in range for the closed-loop users was 75.2% versus 69% for the open-loop users. As the researchers explained, “The time in range increase was equivalent to an extra 90 minutes per day in the closed-loop state compared with the sensor-augmented pump stage, a difference considered clinically significant.” Also, the research team reported that averge time in range overnight (from midnight to 5:59 a.m.) was 10.1 percentage points higher with the closed-loop system, while the time spent in a high-glucose state was lower with the closed-loop system. The closed-loop system also performed better in the areas of blood sugar variability and low blood sugar. The only metric that showed no difference was HbA1c.

The researchers concluded their study by commenting, “Closed-loop therapy is an effective treatment option for older adults with long-duration Type 1 diabetes, and no safety issues were identified. These older adults had higher [time in range] accompanied by less time below range during closed loop than during sensor-augmented pump therapy. Of particular clinical importance, closed loop reduced the time spent in hypoglycemic range overnight.”

Want to learn more about blood glucose management? See our “Blood Sugar Chart,” then read “Blood Sugar Monitoring: When to Check and Why” and “Strike the Spike II: How to Manage High Blood Glucose After Meals.”

Joseph Gustaitis

Joseph Gustaitis

Joseph Gustaitis on social media

A freelance writer and editor based in the Chicago area, Gustaitis has a degree in journalism from Columbia University. He has decades of experience writing about diabetes and related health conditions and interviewing healthcare experts.

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