Frequency of serious diabetes complications lower than in past

After 30 years, the clinical course of type 1 diabetes has changed. The rates of serious diabetes complications appear lower than reported historically — especially when patients are treated intensively, according to a report published in Archives of Internal Medicine.

The Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Research Group analyzed the incidence of long-term complications among participants in the two studies. The analysis included patients with type 1 diabetes originally assigned to intensive therapy and those who received standard therapy until the DCCT trial ended in 1993 and all patients were offered intensive therapy.

The research group also assessed complication rates among participants in the Pittsburgh Epidemiology of Diabetes Complications study, an observational study that included data on patients diagnosed with type 1 diabetes between 1950 and 1980.

"The current analysis of the DCCT/EDIC population looks at the long-term outcomes from a different perspective than the usual analysis of clinical trials in which diabetes complications are reported over study time," David M. Nathan, MD, professor of medicine, Harvard Medical School, told Endocrine Today. "In order to provide a view of modern day clinical outcomes that is more meaningful to providers and patients, we have analyzed the long-term outcomes over a mean 30 years diabetes duration."

Complications over time

After 30 years of diabetes, the cumulative incidence of proliferative retinopathy was 50%, nephropathy was 25% and cardiovascular disease was 14% in the DCCT study. In the EDIC cohort, the cumulative incidence of proliferative retinopathy was 47%, nephropathy was 17% and CVD was 14%.

“The DCCT intensive therapy group had substantially lower cumulative incidences (21%, 9% and 9%) and fewer than 1% became blind, required kidney replacement or had an amputation because of diabetes during that time,” the researchers wrote.

These results are "reassuring," Nathan said.

Historical comparisons are difficult because of differing methods of ascertaining and defining complications, according to the researchers.

However, rates of retinopathy (30%) and nephropathy (12%) in DCCT/EDIC participants after 25 years compare favorably to rates in studies of individuals who developed diabetes 10 to 20 years before (40%-53% for retinopathy; approximately 35% for nephropathy). Rates of functional impairment, such as vision loss and need for kidney transplant, were low in the overall DCCT/EDIC cohort; only three of 1,441 patients became legally blind and 18 required kidney replacement therapy after an average of 25 years.

“The long-term clinical outcome results in the DCCT conventional treatment group, confirmed by the EDC study data, provide a reliable sense of the clinical course that can be expected with modern day therapy during the past 25 years,” the researchers wrote.

Nathan said, "With these results in hand, derived from the largest population of patients with type 1 diabetes studied over a long period of time with standardized, objective methods, we hope to provide patients with a realistic expectation of what their health status should be with intensive therapy. The generally good health of patients with type 1 diabetes after an average 30 years duration is far better than the natural history of diabetes reported in the past."

The results of intensively treated patients provide a view of what patients with type 1 diabetes can expect in the future.

These findings "should further motivate patients with type 1 diabetes to initiate intensive insulin therapy as early in the course of diabetes as possible and continue such efforts over their entire course," Nathan added. - by Katie Kalvaitis

DCCT/EDIC Research Group. Arch Intern Med. 2009;169:1307-1316.