The 30-Year Natural History of Type 1 Diabetes Complications: The Pittsburgh Epidemiology of Diabetes Complications Study Experience

Pambianco G, Costacou T, Ellis D, Becker D, Klein R, Orchard T. Diabetes. 2006;55:1463-1469.

There is a tremendous lack of national data on the long-term complication associated with type 1 diabetes. Thus, the Pittsburgh Epidemiology of Diabetes Complication Study Experience (EDC) was initiated and remains as an ongoing comprehensive investigation of long-term diabetes complications such as mortality, renal failure, proliferative diabetic retinopathy (PDR), overt nephropathy, and coronary artery disease (CAD).

The EDC study is a prospective cohort currently entering its 18th year of follow-up. Juvenile and adolescent patients were recruited from the Children's Hospital of Pittsburgh from 1950-1980. Subsequent baseline examinations were conducted from 1986-1988, with patient assessment performed biennially thereafter. A total of 906 patients with type 1 diabetes were divided into 5 cohorts according to year of diabetes diagnosis: 1950-1959, 1960-1964, 1965-1969, 1970-1974, and 1975-1980. Mortality and morbidity was analyzed for 3 separate time intervals: 20, 25, and 30 years postdiagnosis. Due to the high mortality rates in the early years, complications that could not be determined by death certificates and surveys were examined only in patients who were diagnosed after 1964.

Results indicated that patients who were diagnosed in the later years lived longer. Specifically, at 20 years there was an 84% reduction in cumulative mortality from 1950-1980. There was also 5 times higher rate of early death 25 years postdiagnosis for patients diagnosed in the 1950s than those after 1970, while mortality was 41% lower at 30 years. In addition to reduction in mortality rates, a significant improvement was noted in renal failure rates. At 20 years postdiagnosis, the percentage of patients diagnosed with renal failure was 4 times higher in those diagnosed in the 1950s than those diagnosed after 1964. At 30 years postdiagnosis, the percentage of people with kidney failure further reduced: 31% in the 1950s compared with 18% in the 1960s.

An important finding from the study was that despite new procedures and developments, there was no difference in the rates of cardiovascular events, kidney function, or PDR across the cohorts. Although the reason underlying this discovery is relatively unclear, there is some evidence to suggest that sample size plays a role in the nonsignificant changes. Moreover, failure to show a significant decline in CAD may be due to its moderately attenuated relationship with glycemia. Thus, this places emphasis on the importance of tight blood pressure and lipids control in type 1 diabetes.