Intensive Treatment of Type I Diabetes
Intensive Treatment of Type 1 Diabetes Mellitus has a Continued Benefit in Slowing the Development or Progression of Kidney Disease.
What is the problem and what is known about it so far?
Diabetes mellitus (DM) is a disorder in which the body either does not effectively produce or properly use insulin. Insulin is a substance which helps the body to use sugar from food for energy. As a result, people with DM tend to have high blood sugar “hyperglycemia,” which can cause damage to the kidneys, eyes, and nerves, as well as increase the risk of cardiovascular disease. DM is the leading cause of advanced, irreversible kidney disease (end-stage renal disease) and blindness in the United States. There are two major types of DM (type 1 and type 2), and the number of people with either type is increasing. Fortunately, studies have shown that good control of blood sugar can slow the development and progression of kidney disease, vision loss, and nerve damage.
Why did the researchers do this particular study?
To see if people with type 1 DM who had participated in a study where they received intensive diabetes treatment continued to have a long-term benefit in slowing the development or progression of kidney disease several years after the study had finished.
Who was studied?
This study looked at 1349 people with type 1 DM who had all previously participated in a study called the Diabetes Control and Complications Trial (DCCT) (1983-93). The DCCT compared conventional treatment to intensive treatment for DM:
• Conventional treatment consisted of 1 to 2 insulin injections per day, daily self-monitoring of blood or urine sugar, education about diet and exercise, and checkups every 3 months.
• Intensive treatment consisted of 3 or more insulin injections per day or through an external pump, self-monitoring of dietary intake, exercise, and blood sugar at least four times per day, monthly checkups, and more frequent phone calls and adjustments to ensure that blood sugar readings were in the normal range.
The DCCT showed that people who received intensive treatment had better blood sugar control, as measured by hemoglobin A1C levels, and less occurrence or progression of eye and kidney damage over 3-9 years.
How was the study done?
Beginning in 1993, researchers at 28 different medical centers followed the participants for a further 7 to 8 years. They measured hemoglobin A1C and blood pressure once a year, and measured markers of kidney function (urine albumin and serum creatinine) every other year.
What did the researchers find?
The researchers found that participants who had received intensive treatment in the DCCT had fewer new episodes of kidney disease in the 8 years after the DCCT had ended. This benefit was observed even though the DCCT participants who had received intensive treatment had similar hemoglobin A1C levels at the end of this followup study compared to the participants who had received conventional treatment (8.0% and 8.2%, respectively).
What were the limitations of the study?
This type of study is called an observational study, and as such has some limitations. Most notably, the results (slower development of kidney disease) may not be related to the supposed cause (history of intensive treatment for diabetes), but rather may be the result of some other unsuspected influence. The group evaluated in this follow up period are part of a special study groupso any results may not apply to the general population. Continuing the intensive treatment may confer a higher risk of hypoglycemia, and requires more time and effort than many people might be able to invest.
Finally, it is not clear whether the participants who had previously received intensive treatment would have eventually developed kidney disease at a similar rate to those who had received normal treatment if the study had gone on longer.
What are the implications of the study?
This study suggests that intensive treatment of DM for several years can have a continued benefit at least 8 years later in slowing the development or progression of kidney disease.
Summarized by Kurt H. Kelley, College of Medicine, University of Vermont
Summarized from “Sustained Effect of Intensive Treatment of Type 1 Diabetes Mellitus on Development and Progression of Diabetic Nephropathy: the Epidemiology of Diabetes Interventions and Complications (EDIC) study.” The Writing Team for the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Research Group. Journal of the American Medical Association, Oct 2003, Volume 290, Number 16, pages 2159-2167.
