Generally there are two primary techniques for health providers and patients to evaluate the effectiveness of the management plan on glycemic control: patient self-monitoring of blood glucose or interstitial glucose, and A1C. What should be emphasized is that A1C has a strong predictive value for diabetes complications.
Hyperglycemia defines diabetes, and glycemic control is fundamental to the management of diabetes. Poor controlled hyperglycemia is correlation with diabetes complications such as microvascular complications and cardiovascular diseases (CVD).
Many studies and trials proved that the greatest number of microvascular complications would be averted by taking patients from very poor control to fair or good control. Compared with standard glycemic control (e.g., target A1C <7%), intensive glycemic control (e.g., target A1C <6.5%) seems to have more benefit on the onset or progression of microvascular complications, with further reduction in the risk of microvascular complications.
Despite these confirmed benefit of intensive glycemic control, the risks of lower glycemic targets may outweigh the potential benefits on microvascular complications on a population level when given the substantially increased risk of hypoglycemia. Thus, lower glycemic target is appropriate in selected individuals such as those with short duration of diabetes, little comorbidity, and long life expectancy, as long as significant hypoglycemia dose not become a barrier.
CVD, a more common cause of death in population with diabetes than microbascular complications, is less clearly impacted by levels of hyperglycemia or intensity of glycemic control. Studies about this topic are inconsistent.
In the DCCT, there was a trend toward lower risk of CVD events with intensive control, and in 9-year post-DCCT follow-up of the EDIC cohort participants previously randomized to the intensive arm had a significant 42% reduction in CVD outcomes and a significant 57% reduction in the risk of nonfatal myocardial infarction, stroke, or CVD death compared with those previously in the standard arm.
During the UKPDS trial, there was a 16% reduction in cardiovascular events in the intensive glycemic control arm, although this difference was not statistically significant, and there was no suggestion of benefit on other CVD outcomes such as stroke.
Conversely, results of three more-recent large trials (ACCORD, ADVANCE, and VADT) suggest no significant reduction in CVD outcomes with intensive glycemic control in these populations, who had more advanced diabetes than UKPDS participants. All three of these trials were conducted in participants with more-long-standing diabetes (mean duration 8-11 years) and either know CVD or multiple cardiovascular risk factors.
However, the benefits of intensive glycemic control on CVD primarily rests on long-term follow-up of study cohorts treated early in the course of type 1 and type 2 diabetes and subset analyses of ACCORD, ADVANCE, and VADT.
Lowering A1C to below or around 7% has been shown to reduce microvascular complications of diabetes, and if implemented soon after diagnosis of diabetes is associated with long-term reduction in microvascular disease.
Providers might reasonably suggest more stringent A1C goals (such as <6.5%) for selected individual patients, if this can be achieved without significant hypoglycemia or other adverse effects of treatment. Appropriate patients might include those with short duration of diabetes, long life expectancy, and no significant CVD.
Severe hypoglycemia should be avoid with efforts. Providers should not aggressively attempt to achieve near-normal A1C levels in patients in whom such a target cannot be reasonably easily and safely achieved (with history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, extensive comorbid conditions, and those with longstanding diabetes in whom the general goal is difficult to attain despite DSME, appropriate glucose monitoring, and effective doses of multiple glucose-lowering agents including insulin), where a less-stringent A1C goals (e.g., <8%) might be appropriate.
Table 1 Summary of Glycemic Recommendation for Many Nonpregnant Adults With Diabetes.