Results from the Epidemiology of Diabetes Interventions and Complications (EDIC), study, a continuation of the Diabetes Control and Complication Trial (DCCT), have proven that intensive control has the same positive benefits for cardiovascular disease as for the microvascular complications of diabetes such as eye disease, kidney disease and nerve damage.
The DCCT study, conducted from 1983 to 1993 and funded by the National Institute of Diabetes and Digestive and Kidney Diseases, was the single largest driving force behind the decision to endorse a goal of tight control of blood glucose to prevent microvasular complications for people with type 1 diabetes. Before the DCCT there was no definitive evidence that maintaining better control was preferable.
Approximately 1,400 people aged 13 to 39 with type 1 diabetes were enrolled in DCCT in multiple centers across the United States, including the Joslin Diabetes Center.
Researchers compared the effects of standard management (2 daily injections of insulin plus dietary management), versus intensive management (multiple daily injections of long- and short-acting insulin or pump management, plus modifications in insulin doses based on food intake and exercise) on blood glucose control.
The goal for the intensive group was to keep A1C values close to 6 percent or less. The study showed that normalizing glucose levels as much as possible slows the onset and progression of microvascular problems, such as the eye, kidney, and nerve damage caused by diabetes. In fact, it demonstrated that any sustained lowering of blood glucose was beneficial no mater what the previous control had been.
The DCCT ended in 1993 but research on the study participants didn’t stop there. Over 90 percent of participants have continued in the EDIC trial.
Because participants were relatively young during the years of the DCCT there wasn’t adequate time for macrovasular complications such as cardiovascular disease to develop. EDIC has allowed researchers to compare cardiac outcome differences in participants who were assigned either conventional or intensive care during the DCCT.
The EDIC study is an epidemiological trial which means that participants do not get any intervention—researchers are studying the effects of previous interventions on future outcomes.
By 2003 the parameters used for the intensive control arm of the DCCT was standard care for type 1 diabetes and blood glucose levels between the two groups equilibrated. Despite this, those who received the intensive care during the study still had fewer cardiac events and continued to have better outcomes for microvascular complications as well. This was true even if blood glucose control had deteriorated in the years following the DCCT.
Just as DCCT proved that better control leads to better outcomes for microvascular complications, EDIC showed that Intensive blood glucose control reduces risk of macrovascualr complications significantly. For example, nonfatal heart attack, stroke or death from cardiovascular declined 57 percent.
EDIC is being used to look at more than just macrovasular complications. Researchers have been interviewing trial participants to study the effects of diabetes on cognition for example. By the time the study wraps up in the next year or so there is no telling how much more practical information we may have.