In 1997, the diagnostic criterion for a diagnosis of diabetes was lowered from a fasting glucose tolerance test result of 140 mg/dL to 126 mg/dL (American Diabetes Association, 1997). Based on the diagnostic criteria of a fasting glucose tolerance test of 110 to 126 mg/dL as impaired glucose tolerance and greater than or equal to 126 mg/dL as diabetes, 18.4 percent or 6.3 million people age 65 or older have diabetes. Approximately 40 to 45 percent of persons age 65 years or older have either type 2 diabetes or impaired glucose tolerance. Diabetes is the seventh leading cause of death in the United States, and more than 187,000 persons died from the disease and its complications in 1995 (HCFA, 1999).
Individuals with diabetes mellitus, regardless of type, typically have several risk factors associated with increased morbidity and mortality. The risk factors include abnormal fasting glucose, postprandial glucose, hemoglobin A1c (HbA1c), low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, microalbuminuria, blood pressure, a procoagulant state, and abdominal obesity.
A series of long-term, randomized, controlled trials shows the effect of tight glucose and HbA1c control on complications of the disease and are described below.
Investigators in the Diabetes Control and Complications Trial (DCCT), a randomized controlled trial, followed 1,400 patients with type 1 diabetes, between the ages of 15 and 39 years, for 7 years to determine what effect normalizing blood glucose and HbA1c had on chronic complications of the disease (DCCT Research Group, 1993). The study showed a sustained difference in the levels of glucose and HbA1c between the conventionally treated group and the tightly controlled experimental group. The trial was stopped after 7 years because of the significant lowering of microvascular complication rates in the experimental group compared to the conventionally treated control group. Microvascular disease was defined as retinopathy, neuropathy, and urinary albumin excretion. All three end points showed a significant difference. Macrovascular disease events in diabetes usually include myocardial infarction, sudden death, stroke, and peripheral vascular disease. While the DCCT study lacked the statistical power to detect a difference in macrovascular disease in this relatively young population with type 1 diabetes, a trend toward a lower