In one of the most comprehensive, long-term studies to date of the complications associated with type 1 diabetes, researchers at the University of Pittsburgh Graduate School of Public Health (GSPH) discovered that while cases of premature death and a few other complications have declined, rates of other serious diabetes-related disorders such as heart and eye disease have not improved over the past 25 to 30 years.
In the study, published in the May 1 issue of the journal Diabetes, the investigators analyzed long-term complications such as mortality, renal failure and coronary artery disease in 906 type 1 diabetics participating in the Pittsburgh Epidemiology of Diabetes Complications Study, or EDC. The EDC is an ongoing investigation to document long-term complications of type 1 diabetes among juveniles and adolescents who were patients at Children's Hospital of Pittsburgh between 1950 and 1980.
To conduct their analysis, the University of Pittsburgh researchers and their collaborators divided EDC participants into five groups according to the year their diabetes was first diagnosed: 1950-1959, 1960-1964, 1965-1969, 1970-1974 and 1975-1980. The investigators then analyzed lifespan and illness data among the participants for three separate time intervals: 20, 25 and 30 years post-diagnosis.
Their analysis of mortality data showed that for each group, those diagnosed in later years lived longer. Indeed, individuals diagnosed in the 1950s had a five-fold higher rate of early death at 25 years post-diagnosis than those diagnosed in the 1970s. Some morbidity rates also were reduced. For example, kidney-failure rates declined significantly for those diagnosed more recently. At 20 years post-diagnosis, 4 percent of those diagnosed after 1964 developed renal failure compared to 16 percent among those diagnosed in the 1950s. At 30 years post-diagnosis, renal-failure rates had declined from 31 percent in the 1950s to 18 percent in the 1960s.
On the other hand, there were no differences across cohorts for rates of cardiovascular disease events and cardiac intervention procedures. Even when the researchers took into account the fact that revascularization procedures, such as balloon angioplasty and stenting, have become more common than they were in the 1950s and 1960s, their analysis found no differences in cardiovascular disease among the study population at either 20 or 30 years duration. Finally, there were no differences between the groups in rates of kidney dysfunction or proliferative retinopathy, a major cause of blindness in type 1 diabetics, at 20 and 25 years post-diagnosis.
"Doctors have long considered type 1 diabetes a small blood vessel problem, so they have traditionally not focused on the potential large blood vessel complications, such as cardiovascular disease. However, our study suggests that doctors and their patients need to pay more attention to factors that affect the larger blood vessels, such as lipids and blood pressure," explained Georgia Pambianco, M.S., M.P.H., lead study author, who has been a member of the EDC research staff from its inception.