Epidemiology of Diabetes Interventions and Complications (EDIC): Design, implementation, and preliminary results of a long-term follow-up of the Diabetes Control and Complications Trial cohort

OBJECTIVE - The Diabetes Control and Complications Trial (DCCT) demonstrate d the powerful impact of glycemic control on the early manifestations of mi crovascular complications. Contemporary prospective data on the evolution o f macrovascular and late microvascular complications of type 1 diabetes are limited. The Epidemiology of Diabetes Interventions and Complications (EDI C) study is a multicenter, longitudinal, observational study designed to us e the well-characterized DCCT cohort of >1,400 patients to determine the lo ng-term effects of prior separation of glycemic levels on micro- and macrov ascular outcomes. RESEARCH DESIGN AND METHODS - Using a standardized annual history and physi cal examination, 28 EDIC clinical centers that were DCCT clinics will follo w the EDIC cohort for 10 years. Annual evaluation also includes resting ele ctrocardiogram, Doppler ultrasound measurements of ankle/arm blood pressure , and screening for nephropathy At regular intervals, a timed 4-h urine is collected, lipid profiles are obtained, and stereoscopic fundus photographs are taken. In addition, dual B-mode Doppler ultrasound scans of the common and internal carotid arteries will be performed at years 1 and 6 and at st udy end. RESULTS - Written informed consent was obtained from 96% of the DCCT subjec ts. The participants, compared with nonparticipants, tended to have better glycemic control at the completion of the DCCT and were more likely to have their diabetes care provided by DCCT personnel. The EDIC baseline measurem ent stratified by sex delineates multiple cardiovascular disease risk facto r differences such as age (older in men), waist-to-hip ratio (higher in men ), HDL cholesterol (lower in men), hypertension (more prevalent in men), an d maximum intimal-medial thickness of common and internal carotid arteries (thicker in men). Of the original conventional treatment group, 69% have ch anged to continuous subcutaneous insulin infusion or multiple daily injecti ons. Although the mean HbA(1c) difference between the intensive and convent ional treatment groups narrowed at EDIC years 1 and 2, HbA(1c) remained sig nificantly lower in the intensive group. Of all expected clinic visits, 95% were completed, and the quality of EDIC data is very similar to that obser ved in the DCCT. CONCLUSIONS - Although obvious problems exist in extended follow-up studies of completed clinical trials, these are balanced by the value of continued systematic observation of the DCCT cohort. In contrast to other epidemiolo gic studies, EDIC will provide 1) definitive data on type 1 as distinct fro m type 2 diabetes; 2) reliance on prospective rather than on cross-sectiona l analysis; 3) long-term followup in a large population; 4) consistent use of objective, reliable measures of outcomes and glycemia; and 5) observatio n of patients from before the onset of complications.