Does Variability in Sugar Control Increase Cardiovascular Risk in Diabetes?

There is emerging evidence that variability in blood sugar control can increase cardiovascular risk. A new study adds to the data in this area.

The study, published in Diabetes Care, looked at the data on over 19,000 patients in Scotland with newly diagnosed diabetes, to evaluate whether fluctuations in hemoglobin A1C measurements was associated with a higher risk of diabetes complications.

They found that over a median of 6.8 years, for people for whom over 60% of their A1Cs varied by more than 0.5%, compared to those in the lowest quintile for A1C variability, there was:

over double the risk for each of death, heart attack, and stroke
over 3 times higher risk for each of heart failure, diabetic nerve disease, and diabetic kidney disease
over 5 times higher risk of diabetic foot ulcer
over 7 times higher risk of diabetic eye disease

While the authors did adjust for a number of variables to confirm the robustness of their results, we still have to keep in mind that this is a retrospective analysis and thus subject to possible confounding factors. In other words, we can’t be certain that the A1C variability is the direct cause of the results seen. For example, differences in types of medications taken by these people may have played a role; some diabetes medications can reduce cardiovascular risk independent of blood sugars. That being said, the magnitude of differences in risk seen in this study is quite compelling, and is in line with existing data on this topic.

So how can variability in blood sugar control increase risk of diabetes complications? Possibilities include:

oxidative stress (we believe this to be an explanation for the association of short term blood sugar variabiltiy and cardiovascular risk)
epigenetic changes induced by variability in blood sugars
a higher risk of low blood sugars in people with variable sugar control (if they are taking medications that can cause low sugars (eg insulin, sulfonylureas))

BOTTOM LINE: Good diabetes control, and consistent diabetes control, is important in preventing diabetes complications.

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