Risks of High and Low A1C Levels for Diabetics
Continuous sensors will change everything for people with diabetes. That’s the view of some top diabetologists who met in Washington, D.C., on December 19.
The National Institutes of Health, the U.S. Food and Drug Administration , and the Juvenile Diabetes Research Foundation International organized the meeting to discuss “Obstacles and Opportunities on the Road to an Artificial Pancreas: Closing the Loop.” While they haven’t published their discussions, I just got an extensive draft of the discussions from diabetes consultant Kelly Close, who has a summary on her website.
Reading what those experts said convinced me that diabetes control is about to take as big a leap forward as it did in the early 1990s when the conclusions of the Diabetes Control and Complications Trial (DCCT) became clear. The DCCT showed that people with diabetes who keep their A1C levels close to 7 percent have a much better chance of delaying or preventing diabetes complications that affect the eyes, kidneys and nerves than people with levels of 8 percent or higher.
The DCCT proved the importance of the A1C. The conventional wisdom before then was that high levels of injected insulin or possibly reactions to those shots caused the complications of diabetes. This is not true.
But an A1C level of below 7 percent can mask a lot of highs and lows. The experts call these hypos and hypers “glycemic variability” or “glycemic excursions.” Your fingerstick numbers can be all over the place, while your A1C looks fine.
There is a growing consensus that glycemic excursions leading to oxidative stress are another risk factor in addition to high A1C levels. For example, a blood glucose level of 180 for just 90 minutes can lead to a 24-hour shut down of an enzyme that helps prevent hardening of the arteries. Dr. Michael Brownlee of Albert Einstein College of Medicine presented this unpublished study of people without diabetes at the meeting.
Until now, we never had any idea how many excursions we have been taking and didn’t even know that we had to reduce them. That’s because people with diabetes are just beginning to use continuous sensors that provide real time feedback.
The Guardian RT from Medtronic Diabetes is now available in seven cities. The FreeStyle Navigator from Abbott Laboratories and the DexCom STS each have premarket approval applications pending right now before the FDA. Full disclosure: I own DexCom (DXCM) stock.
In October and January, Diabetes Care published two studies that show just how bad our excursions have become. The first recruited 60 people with type 1 and 41 with type 2 to wear Navigator monitors. None of these 101 people could see the 1.7 million continuous glucose measurements, so this study showed what people are doing now. Typically, these people were hyperglycemic – above 180 mg/dl – 7 hours a day. They were hypoglycemic – below 70 mg/dl – two hours a day.
Didn’t they know what they were doing? In fact, they knew much more than most of us, doing traditional fingerstick tests 10 times a day.
“That’s shocking,” says Aaron J. Kowalski, Ph.D., the director of strategic research projects at the Juvenile Diabetes Research Foundation. He brought this and the next study to my attention.
The other study recruited 75 types 1s and 16 type 2s to wear DexCom STS monitors. In the first part of the study they weren’t allowed to see their blood glucose readings, the so-called “blinded period.” But once unblinded, they reduced the time they spent in the hypoglycemic range (defined here as below 55 mg/dl) by 9 percent. Likewise, they reduced the time they spent in the hypoglycemic range (above 240 mg/dl) by 15 percent.
Few people with diabetes have yet had the opportunity to wear a continuous sensor, but Kelly Close is one.
“The absence of fingersticks, to me, is only one tiny part of the advantage of continuous sensors,” she told me. “Knowing the direction of rate and change in blood glucose helps to predict and avoid hypoglycemia and hyperglycemia, and alarms that indicate high and low blood sugars help you minimize glucose excursions. More than anything, the piece of mind and freedom from uncertainty and fear that continuous sensors can provide is powerful. When I was wearing a continuous monitoring device, I felt, for the first time since I was diagnosed, that the burden of always wondering and worrying about my blood glucose levels was gone. It was almost as if I didn’t have diabetes.”
The conclusion has to be that an A1C below 7 percent is necessary for us to stay in good health. But it’s not sufficient. We also have to stop taking those trips away from normal blood glucose levels. When we start wearing continuous sensors, it will be a lot easier for us to avoid serious complications.
Published On: February 13, 2006