SOURCE: Kovatchev B, Cobelli C. Glucose variability: Timing, risk, analysis, and relationship to hypoglycemia in diabetes. Diabetes Care 2016;39:502-510.
The benefits of glycemic control in type 2 diabetes (T2DM) include improved microvascular status (retinopathy, neuropathy, nephropathy) and better quality of life. Striving for progressively better control of hyperglycemia is typically associated with an increased incidence of hypoglycemia, consequences of which can range from transient unpleasant central nervous system dysfunctions and signs of autonomic activation to coma and death.
While A1c is an accurate measure of mean glucose levels, two individuals with the same A1c level can present markedly different excursions of glucose above and below the mean, which generates A1c. Typically, higher glucose variability above and below the mean reflects more episodes of greater hyperglycemia as well as hypoglycemia, which may not be readily discerned through just examining A1c. Continuous glucose monitoring, as well as frequent self-monitoring of blood glucose, have created a window of observation to detect glucose variability.
What’s the practical yield of attending to glucose variability? There is still some disagreement about the best way to measure variability, since hyperglycemic excursions typically are much less concerning than similar reductions toward hypoglycemia, so it may be necessary to use separate metrics for hypo- vs. hyperglycemic variability. Additionally, computations to assess glucose variability are not paper-and-pencil simple — they require computational tools. However, it has been shown that, as an example, at the same A1c level, glucose variability was substantially less in patients taking oral agents who added a GLP1-RA (e.g., exenatide) vs. insulin glargine. While not yet a tool for routine practice, analysis of glucose variability appears to hold promise for the future.