The importance of glycemic control: how low should we go with HbA1c? Start early, go safe, go low

Epidemiologic data indicate a continuous relationship between hemoglobin A1c (HbA1c) and risk for microvascular and macrovascular complications of diabetes. Intensive glycemic control reduces risk of microvascular complications in Type 1 and Type 2 diabetes, and long-term treatment and follow-up studies have shown that initial intensive control is associated with reduced cardiovascular risk. Recent intervention trials in older, high-risk patients with Type 2 diabetes have not shown a benefit of intensive control in reducing cardiovascular risk over a rather short-term follow-up period of up to 5 years, with some data indicating that intensive control accompanied by hypoglycemia is detrimental in patients with high cardiovascular risk. Indeed, hypoglycemia with current antidiabetic agents--primarily insulin and sulphonylureas--is the main limiting factor in achieving desirable levels of glycemic control. Still, the goal in treating both Type 1 and Type 2 diabetes should be to safely get HbA1c as close to normal as possible. In Type 2 diabetes, this goal should be tempered for the time being in patients with shorter life expectancy or co-existing cardiovascular disease or other co-morbidities, in whom a target of 7.0-7.5% may be advisable until we can demonstrate that lower targets in such patients can be safely achieved. Newer agents with lower risk of hypoglycemia--e.g., insulin analogues, incretin mimetics and incretin enhancers-may form an integral component of strategies for safely achieving lower HbA1c levels.