It is always appropriate to provide good news; but even more exciting when a study continues to "keep on giving." The 1993 Diabetes Control and Complications Trial (DCCT), which is likely the most quoted trial in the history of scholarly diabetes, continues to provide further promising news in regard to diabetes microvascular complications.
To review, the DCCT enrolled 1,441 people with type 1 diabetes and randomly assigned them into two groups over 6.5 years. The first group had intensive insulin therapy in which people with diabetes received three or more injections of insulin/day (including insulin pump therapy) aimed at achieving blood sugars levels in a near normal range. The second group had conventional insulin therapy to avoid symptoms related to hyperglycemia. The mean hb A1c during the DCCT study from 1983-1993 was 7.3 percent in the intensive insulin therapy group and 9.1 percent in the conventional insulin therapy group. In the 12/23/11 issue of The New England Journal of Medicine, the writing group of the DCCT/EDIC (Epidemiology of Diabetes Interventions and Complications study) published Intensive Diabetes Therapy and Glomerular Filtration Rate in Type 1 Diabetes (NEJM 365; 25: 2366-2375).
After the DCCT, the EDIC trial followed 1,375 people who participated in the DCCT to study the future development of diabetes complications. Kidney function tests (blood creatinine levels and glomerular filtration rates) were evaluated. The glomerular filtration rate is an extremely important indicator of kidney function. As the GFR decreases, the risk of kidney failure increases proportionately. In addition, once the GFR becomes impaired, the development of kidney failure along with cardiovascular disease increases at significantly higher rates.
What did the investigational team find?
1. After a follow-up period of 22 years, impairment of the GFR developed in 24 and 46 participants assigned to intensive insulin therapy and conventional therapy, respectively. This represents a 50 percent risk reduction with intensive insulin therapy.
2. Among these participants, end-stage renal disease developed in 8 and 16 study participants assigned to intensive insulin therapy and conventional insulin therapy, respectively.
The implications and conclusions of this study are significant. Most importantly, the risk of impaired glomerular filtration rate (major indicator of kidney function as described above) was lower among persons treated EARLY in the course of diabetes with intensive insulin therapy than among those treated with conventional insulin therapy. In addition, the intensive lowering of blood sugar levels for an average of 6.5 years (DCCT) in people with Type 1 Diabetes reduced the incidence of impaired GFR by 50 percent. The authors conclude that this study "provides strong evidence that impairment of the GFR may be prevented in patients with type 1 diabetes and reinforces the importance of early glycemic control."
As a specialist in pediatric diabetes, this conclusion is essentially my reason for existence! Once again, we have evidenced-based research that reinforces the conclusion that control of blood sugars will lead to a decrease in microvascular (eye, kidney, nerves) and macrovascular (cardiovascular) complications. There have been other studies that support decrease in microvascular complications as well with tight control (see previous blog about retinopathy). It is clear that tight control is particularly important early in the treatment of type 1 (and type 2) diabetes. As the vast majority of people who develop type 1 diabetes are children or young adults, it is often the responsibility of the pediatric diabetes team to attempt to help our patients achieve the best glucose control as possible.