By Amy Adams, MS

Reviewed By Jeremy Walston, MD
Last Updated: September 15, 2000

In people with Type 1 diabetes, the immune system attacks the cells in the pancreas that make insulin. Without insulin, muscle and fat cells are unable to use sugar from the blood as fuel. The sugar, called glucose, builds up to very high levels, which can damage blood vessels, nerves, kidneys, and eyes.

Most diabetes treatment plans lower a diabetic's blood sugar level, but do not achieve the levels of a nondiabetic person. A recent study called the Diabetes Control and Complications Trial (DCCT), however, found that keeping blood sugar levels as close to normal as possible significantly reduced the damage to eyes, kidneys, and nerves caused by high blood sugar. However the increased risk for heart disease was not reduced in this trial.

The DCCT

The DCCT studied 1,400 Type 1 diabetics for an average of seven years to find out if significantly lowering blood glucose levels would reduce diabetic complications such as eye, nerve, or kidney disease. Half the study group continued their usual treatment plan, while the other half maintained extremely tight control over their blood sugar levels — attempting to keep those levels as close to those of nondiabetic people at all times.

People who exercised tight control over their blood sugar had significantly less damage to their eyes, kidneys, and nerves

Overall, people who exercised tight control over their blood sugar had significantly less damage to their eyes, kidneys, and nerves. In fact, the results were so striking that doctors ended the trial early in order to bring all patients over to the tight control treatment.

Maintaining tight regulation was time consuming and costly, and the people in the tight control group had triple the normal risk of low blood sugar episodes. (The brain relies exclusively on glucose for energy, so extremely low blood sugar levels can result in tiredness, headache, confusion, or even unconsciousness.) However, because of the significant decrease in diabetic complications, the American Diabetes Association recommends maintaining tight control over blood sugar levels in all Type 1 diabetics. The only exceptions to this rule are children less than two years of age. The American Diabetes Association also recommends using care in maintaining tight blood sugar control in children between the ages of two and seven because low blood sugar episodes may impair brain development.

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Eye Damage

Nearly all Type 1 diabetics have some degree of eye damage (retinopathy) within 20 years of being diagnosed with the diabetes. However, the DCCT found that by maintaining tight control over blood sugar levels, Type 1 diabetics could reduce their risk of eye disease by 76 percent.

Because the retina can be irreversibly damaged before you notice any changes in vision, and because retinopathy can be treated to minimize vision loss, the American Diabetes Association recommends screening for retinopathy yearly starting at the age of ten or between two and five years after being diagnosed with Type 1 diabetes.

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Kidney Disease

Kidney disease (nephropathy) affects more than 30 percent of people with Type 1 diabetes. In the DCCT, those who maintained tight control over their blood sugar levels had 50 percent lower risk of developing kidney disease than those on a normal treatment plan.

Because of the serious consequences of kidney disease, the American Diabetes Association recommends screening for protein in the urine every year starting at the time of diagnosis, or five years after the diagnosis in Type 1 diabetics.

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Nerve Disease

Nerve damage (neuropathy) affects 60 percent of all people with diabetes. In the DCCT, those who maintained tight blood sugar control had 60 percent less risk of developing neuropathy than people following conventional therapy. Nerve damage in the feet can allow small cuts or scratches to go unnoticed, seriously damaging the feet. Because of these consequences, the American Diabetes Association recommends that all people with diabetes have a thorough foot exam every year.

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Heart Disease

People with diabetes have two to four times the risk of developing heart disease or stroke than the general population. This risk does not seem to be caused by high blood sugar: In the DCCT, the group that maintained tight control over their blood sugar did not have significantly lower risk of heart disease. For this reason, the American Diabetes Association recommends that people with diabetes follow the same guidelines for heart disease — such as keeping blood pressure levels under control — as the general population to reduce their higher risk of heart disease. (For news about how to prevent heart disease associated with Type 1 diabetes, see Related News below.)

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Related News

In order to view these articles you will need to have a MyGeneticHealth account. If you are not already a member, selecting the article will automatically take you to a page where you can sign up. Vitamin E may help heart in type 1 diabetics

References

Diabetes Control and Complications Trial Research Group. (1993). The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med 329: 977-986.

American Diabetes Association (1999). Clinical Practice Recommendations 1999 Diabetes Care (Suppl. 1) 22: S1-S114.

National Institute of Diabetes and Digestion and Kidney. (1999). Diabetes Statistics Bethesda, MD; National Institutes of Health. Publication No. 99-3892

Mayfield JA et al. (1998). Preventive foot care in people with diabetes (Technical Review) Diabetes Care 21: 2161-2177.