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Diabetes Control and Complications Trial (DCCT)

What Is the DCCT?

The DCCT is a clinical study conducted from 1983 to 1993 by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The study showed that keeping blood sugar levels as close to normal as possible slows the onset and progression of eye, kidney, and nerve diseases caused by diabetes. In fact, it demonstrated that any sustained lowering of blood sugar helps, even if the person has a history of poor control.

The largest, most comprehensive diabetes study ever conducted, the DCCT involved 1,441 volunteers with type 1 diabetes and 29 medical centers in the United States and Canada. Volunteers had diabetes for at least 1 year but no longer than 15 years. They also were required to have no, or only early signs of, diabetic eye disease.

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The study compared the effects of two treatment regimens--standard therapy and intensive control--on the complications of diabetes. Volunteers were randomly assigned to each treatment group.

DCCT Study Findings

Lowering blood sugar reduces risk:

  • Eye disease
    76% reduced risk
  • Kidney disease
    50% reduced risk
  • Nerve disease
    60% reduced risk

How Did Intensive Treatment Affect Diabetic Eye Disease?

All DCCT participants were monitored for diabetic retinopathy, an eye disease that affects the retina. Study results showed that intensive therapy reduced the risk for developing retinopathy by 76 percent. In participants with some eye damage at the beginning of the study, intensive management slowed the progression of the disease by 54 percent.

The retina is the light sensing tissue at the back of the eye. According to the National Eye Institute, one of the National Institutes of Health, as many as 24,000 persons with diabetes lose their sight each year. In the United States, diabetic retinopathy is the leading cause of blindness in adults under age 65.

How Did Intensive Treatment Affect Diabetic Kidney Disease?

Participants in the DCCT were tested to assess the development of diabetic kidney disease (nephropathy). Findings showed that intensive treatment prevented the development and slowed the progression of diabetic kidney disease by 50 percent.

Diabetic kidney disease is the most common cause of kidney failure in the United States and the greatest threat to life in adults with type 1 diabetes. After having diabetes for 15 years, one-third of people with type 1 diabetes develop kidney disease. Diabetes damages the small blood vessels in the kidneys, impairing their ability to filter impurities from blood for excretion in the urine. Persons with kidney damage must have a kidney transplant or rely on dialysis to cleanse their blood.

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