Am Fam Physician. 2009;80(10):1167-1170
Guideline source: American Diabetes Association; American College of Cardiology Foundation; and American Heart Association
Literature search described? No
Evidence rating system used? Yes
Published source:Circulation, January 20, 2009
Diabetes is defined by its association with microvascular complications specific to high blood glucose levels, but it also confers a higher risk of cardiovascular disease, which is the leading cause of death in persons with diabetes. Intensive glycemic control in patients with type 1 and type 2 diabetes mellitus can reduce the risk of microvas-cular complications, but whether it can reduce the risk of cardiovascular events is less clearly defined. Accordingly, the American Diabetes Association (ADA) recommends an A1C goal of less than 7.0 percent for most adults with diabetes (Table 1). However, there may be a reduction in the risk of new or worsening albuminuria when median A1C is lowered to 6.3 percent, compared with standard glycemic control (i.e., A1C of 7.0 percent).
| Recommendation | Level of evidence |
|---|---|
| To reduce microvascular and neuropathic complications of type 1 and type 2 diabetes, the A1C goal is less than 7.0 percent for nonpregnant adults in general. | ADA: A-level recommendation* |
| ACC/AHA: Class I recommendation (level of evidence: A)† | |
| To reduce the risk of macrovascular disease in persons with type 1 and type 2 diabetes, the A1C goal is less than 7.0 percent. | ADA: B-level recommendation* |
| ACC/AHA: Class IIb recommendation (level of evidence: A)† | |
| An A1C goal greater than 7.0 percent may be appropriate for patients with a history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, or extensive comorbidities. It may also be appropriate for those with long-standing diabetes in whom the general goal is difficult to attain despite diabetes self-management education, appropriate glucose monitoring, and effective doses of multiple glucose-lowering agents, including insulin. | ADA: C-level recommendation* |
| ACC/AHA: Class IIa recommendation (level of evidence: C)† | |
| An A1C goal lower than the general goal of less than 7.0 percent may be beneficial for certain patients if it can be achieved without severe hypoglycemia or other adverse effects of treatment. Such patients might include those with a short duration of diabetes, long life expectancy, and no cardiovascular disease. | ADA: B-level recommendation* |
| ACC/AHA: Class IIa recommendation (level of evidence: C)† |
The benefits of intensive glycemic control on micro-vascular and neuropathic complications are well established for type 1 and type 2 diabetes. Although randomized controlled trials of intensive versus standard glycemic control have not shown a significant reduction in cardiovascular disease outcomes in type 1 and type 2 diabetes during the randomized portion of the trials, long-term follow-up data suggest that A1C targets below or near 7.0 percent in the years soon after the diagnosis of diabetes are associated with long-term risk reduction.
Persons with type 1 diabetes tend to have lower rates of obesity, hypertension, and dyslipidemia than those with type 2 diabetes, but they are also at a high lifetime risk of developing cardiovascular disease. Compared with that for type 2 diabetes, the evidence for a cardiovascular benefit of intensive glycemic control is strongest for persons with type 1 diabetes, but patients who have a short duration of type 2 diabetes without established atherosclerosis also might show improved cardiovascular outcomes from intensive glycemic control.
The potential risks of intensive glycemic control may outweigh its benefits in some patients with type 2 diabetes, including older adults, those who have had the disease for many years, or those with severe hypoglycemia, advanced atherosclerosis, or frailty. Current treatment approaches for hyperglycemia in patients with advanced type 2 diabetes may have adverse effects that are counterproductive in reducing the risk of cardiovascular disease, such as hypoglycemia, weight gain, or other metabolic changes. Prevention of severe hypoglycemia in patients with advanced disease is important, and physicians should not aggressively strive for near-normal A1C levels in these patients when this cannot be achieved safely.
In addition to recommending glycemic control to reduce the risk of cardiovascular disease in persons with diabetes, the ADA and American Heart Association also recommend controlling nonglycemic risk factors. This includes blood pressure control, use of statins to lower lipid levels, aspirin prophylaxis, smoking cessation, and healthy lifestyle behaviors.