0 Glycemic Variability

How much do your blood sugars vary in a day?

The answer to this question might have more of a bearing on your risk for complications than your HbA1c alone. Dr. Irl Hirsh (shown) reviewed data on fluctuations in blood glucose. In his 2005 paper he reported: ¹

"New data, however, show that glucose variability, independent of A1C, may also play a significant role in the risk for complications."

He cited an example from the landmark 1993 Diabetes Complications and Control Trial:

"For example, the risk of retinopathy in control patients with an A1C of 9% was approximately 2.5 times greater than the risk of experimental patients with a 9% A1C. The only significant difference between these groups is that 90% of the control group was on twice-daily NPH insulin to cover basal and prandial insulin needs, whereas subjects in the experimental group were on basal-bolus therapy using either NPH insulin twice daily and regular insulin at meals, multiple daily injections, or an insulin pump."

Dr. Hirsch suggested that blood sugars not deviate by more than a third of average blood sugar. If your average BG was 120 mg/dl, you would not want it to fluctuate by more than 40 mg/dl, e.g. you would not want it to go higher than 160 mg/dl.

A goal for therapy that addresses both chronic high blood sugars (hyperglycemia) and glycemic variability was discussed in a recent article in the journal Diabetes Care (February Supplement): ²

"It is strongly suggested that a global antidiabetic strategy should be aimed at reducing to a minimum the different components of dysglycemia (i.e., A1C, fasting and postprandial glucose, as well as glucose variability). All the therapeutic agents that act on postprandial glucose excursions seem of particular interest for reducing the latter parameter (i.e., the glucose instability)."

Managing glycemic variability cannot be adequately accomplished without knowledge of blood sugar variations - which makes regular blood sugar monitoring essential:

"In patients with type 2 diabetes, SMBG* should be performed with increased frequency to monitor glycemic variability, regardless of the effect on HbA1c."
- Glycemic Variability: A Hemoglobin A1c–Independent Risk Factor for Diabetic Complications, Brownlee M and Hirsch I, JAMA, 2006.

* Self-Monitored Blood Glucose

The above makes a good argument for increased use of continuous monitors.
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¹ Glycemic Variability: Its Not Just About A1C Anymore! , Diabetes Technology and Therapeutics, 2005.
² Glycemic Variability, Should We And Can We Prevent It? , Diabetes Care, 2008.