Because persons with diabetes are at increased risk for cardiovascular disease, the leading cause of death in the United States, the atherogenic consequences of diabetes account for an enormous burden of suffering and rising health care expenditures in the United States. Type 1 diabetes usually has its onset during childhood and is characterized by low or absent levels of insulin, autoimmune response leading to beta-cell antibodies as well as antibodies to other components of the islets, and genetic predisposition. Genetic predisposition is even more evident in type 2 diabetes. A strong body of evidence suggests that the incidence of microvascular complications can be reduced significantly by therapeutic measures to lower blood glucose to normal or near-normal levels. The implications of this evidence for blood glucose control are debated, however.
Microvascular complications require a number of years to develop into symptomatic disease.
The generally younger patients with type 1 diabetes are more likely to live long enough to experience the benefits of tight glycemic control than are older patients with type 2 disease, who face a shorter life expectancy by virtue of their age and risk of cardiovascular disease. Although several observational studies have shown a correlation between hyperglycemia and mortality, there is only limited evidence that glycemic control can reduce the risk of macrovascular complications. These tradeoffs are not uniform for all patients with type 2 diabetes. Although the older age of onset that is typical of type 2 diabetes results in a lower average lifetime probability that microvascular complications will develop than is typical of type 1 diabetes, a significant proportion of patients with type 2 diabetes do live long enough to experience significant microvascular disease. The older age of onset reflects a population average with a wide age distribution, and thus an important subset of individuals with type 2 diabetes develop the disease earlier in life and are more likely to benefit from glycemic control.