Could Continuous Glucose Monitoring (CGM) Lower Your A1C Long-Term?

CGM, regardless of insulin delivery method, lowered A1C best, two-year study finds.

If you have type 1 diabetes and are struggling to keep your A1C at goal, maybe continuous glucose monitoring (CGM) is your answer.

CGM and A1C

Before you say, ''But I'm not on a pump," or "I don't want to use a pump," hold on. The researchers found that the CGM improved A1C over the two-year study regardless of how the insulin was delivered.

"It is not so important how the insulin is injected (pump or pen),'' says Jan Soupal, PhD, a researcher at the Charles University in Prague, Czech Republic, who led the study. What's crucial, he found, is how you monitor your blood glucose. He found that CGM was superior.

Those using CGM in his study had lower AICs—going from 8.3% at the study start to 7.1% over the two years. They also had fewer episodes of low blood sugar and less variability. Dr. Soupal presented the research at the European Association for the Study of Diabetes (EASE) 2017 meeting in Lisbon. 1
It's too soon to say the findings apply to those with type 2 diabetes, Dr. Soupal says.

Details: CGM, Research

A CGM system includes a tiny glucose sensor, or electrode, inserted under the skin. It measures glucose in the tissue fluid. The electrode is connected to a transmitter that relays information to a monitoring and display device. If your glucose drops too low or rises too much, an alarm sounds.
While other research has found CGM helpful to control blood sugar, Dr. Soupal believes this one is the first to look in ''real life,'' looking at four different strategies, and to follow the patients for two years.
A total of 65 patients were in the study:

  • 27 used CGM--15 on pump, 12 on multiple daily injections (MDIs)
  • 20 were on continuous subcutaneous insulin infusion (CSII) without CGM
  • 18 were on MDIs and self-monitoring of blood glucose (SMBG)

All went through four days of training. The improvements in the CGM users were stable over the two-year follow-up.


Expert Input

"This is the first long-term, real-life data we have to say, 'Yes, our intuitions were correct," says Amy Hess-Fischl, MS, RD, LDN, BC-Adm, CDE, a certified diabetes educator and program coordinator for the Teen and Adolescent Diabetes Transition Program at the University of Chicago Kovler Diabetes Center. She is on the Endocrine Web editorial board. "We know A1C is directly affected when blood glucose levels are high for a longer period of time, so having CGM, regardless of insulin delivery type, will improve blood glucose overall."

However, she says, that A1C is just one part of the equation. "Time in range, reducing glycemic variability, is the most important component for achieving a real reduction in A1C since wide fluctuations will make the A1C look better than it is).'' In the study, the CGM also reduced glycemic variability better, Dr. Soupal found.
That also makes sense, Hess-Fischl says. "Since the CGM gives readings every few minutes, people have access to hundreds of readings per day (instead of standard 2-6 times per day) and have alerts when they are riding above their target, meaning they can make adjustments to bring themselves back in range sooner."

One caveat: Learning how to manage CGM typically takes time, patience and education, Hess-Fischl says. Put in the time, she suggests, to learn patterns and how to identify if the insulin doses are correct. Get help, she says, from your health care provider and a certified diabetes educator who specializes in type 1 diabetes.

Hess-Fischl is a consultant for Roche Diabetes Care and on the speakers' bureau for Sanofi. 


Updated on: September 21, 2017
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