A method of intensive diabetes self-management that involves keeping blood glucose levels as close as possible to normal without causing severe or frequent episodes of hypoglycemia (low blood sugar), in the aim of preventing complications of diabetes. The term “tight control” has been around for decades, as researchers hotly debated whether aggressive blood glucose control could lower the risk of developing diabetic complications, including eye disease, kidney disease, and nerve disease. In recent years, a number of large clinical trials put the debate to rest. Based on the results of these trials, the American Diabetes Association (ADA) began to define tight control in terms of numeric values and urged most people with diabetes to strive for these more stringent goals. Even so, experts say that no single range of blood glucose levels works for everyone, and that these goals must be individualized.
In the Diabetes Control and Complications Trial (DCCT), which ended in 1993, 1,441 people with Type 1 diabetes were randomly assigned to receive either standard diabetes care or intensive insulin therapy. While the standard care group had one or two insulin injections per day, the intensive care group was treated with three or more daily insulin injections or insulin pump therapy, had frequent contact with health-care providers, and checked their blood glucose level four or more times a day. After an average of 6.5 years of therapy, the standard care group had an average glycosylated hemoglobin (HbA1c) level of about 9%, while the intensive care group achieved an HbA1c level of 7%. (The HbA1c level indicates a person’s average blood glucose level over the previous two to three months and is a good measure of how well blood glucose is being controlled. The average for people who don’t have diabetes is less than 6%.) More important, researchers found that the intensive care group had significantly lower rates of diabetic eye disease, diabetic kidney disease, and diabetic nerve disease. Years after the completion of the DCCT, the average HbA1c for all participants had leveled to around 8%, but those who had practiced tight control during the study continued to have fewer complications.
The results of follow-up studies, published in 2003 and 2005, showed that the DCCT participants who had practiced tight control also lowered their risk of atherosclerosis and heart disease.
An even larger clinical trial, the United Kingdom Prospective Diabetes Study (UKPDS), studied the effects of intensive blood glucose control in over 5,000 adults newly diagnosed with Type 2 diabetes. In this study, the standard care group was treated with lifestyle interventions alone (diet and exercise) unless symptoms of severe hyperglycemia (high blood glucose) developed and pharmacologic intervention became necessary. The intensive care group was treated with insulin, metformin, or a sulfonylurea drug such as glyburide (brand names Micronase, DiaBeta, Glynase), or a combination of these. At the end of the study, the standard care group had an average HbA1c of 7.9%, while the intensive care group had attained an HbA1c of 7%. Although this may not seem like a big difference, the intensive care group had a significantly lower rate of all complications of diabetes. In particular, for each 1% reduction in HbA1c level (for example, from 9% to 8%), there was a 35% reduction in the risk of developing microvascular (small-blood-vessel) complications like eye disease, kidney disease, and nerve disease.