Here's yet another reason for people with type 1 diabetes to keep their blood sugar under tight control: Doing so can dramatically reduce their risk of heart attacks, stroke, and other cardiovascular problems. Type 1 diabetes is a less common form of the condition, and occurs when the pancreas produces little-to-no insulin. Once referred to as "juvenile diabetes," it occurs in 5% to 10% of diabetes cases.
Earlier studies have shown that using intensive therapy to keep blood sugar levels as close to normal as possible can cut the chance of developing a number of diabetes-related complications, including eye, nerve, and kidney damage. But a study presented by researchers at the annual scientific meeting of the American Diabetes Association (ADA) adds the benefit of reducing the risk of heart disease to the list.
"The longer we follow patients, the more we're impressed by the lasting benefits of tight glucose control," said Dr. Saul Genuth, one of the study's co-chairs, in a statement released by the ADA. "The earlier therapy begins and the longer it is maintained, the better the chances of reducing the debilitating complications of diabetes."
The study looked at the long-term effects of using intensive therapy, compared to a more conventional approach, to control the blood sugar of more than 1,400 people with type 1 diabetes. In the study, people between the ages of 13 and 39 were randomly assigned to either an intensive treatment group or a conventional treatment group.
Participants in the intensive treatment group received at least three insulin injections per day in order to regulate blood sugar, or they used an insulin pump, which injects a steady stream of insulin into the bloodstream and allows for adjustments during meal times. Blood sugar control was monitored through frequent self-testing as well as through regular blood tests measuring participants' hemoglobin A1c levels, which would reflect average blood sugar control over recent months.
In the conventional treatment group, participants received one or two insulin injections per day and underwent daily urine or blood tests to measure their blood sugar levels.
After 6.5 years, hemoglobin A1c levels averaged 7% in the intensive treatment group and 9% in the conventional treatment group. The researchers define normal hemoglobin A1c levels as 6% or less.
Though the study ended after 6 years, 1,375 of the subjects participated in a follow-up study for an additional 17 years. Among those participants, there was a greater incidence of heart problems in the conventionally treated group than in the intensively treated group. Overall, there were 46 "cardiovascular disease events" (heart attack, stroke, angina, coronary artery disease requiring angioplasty, or bypass surgery) in the intensive group and 98 in the conventional group. A total of 4% or 31 of the intensively treated participants experienced these events, compared to 7% or 52 of the conventionally treated participants.
"The risk of heart disease is about 10 times higher in people with type 1 diabetes than in people without diabetes," said study co-chair Dr. David Nathan in a press release. "It's now clear that high blood sugar levels contribute to the development of heart disease. The good news is that intensively controlling glucose significantly reduces heart disease as well as damage to the eyes, nerves, and kidneys in people with type 1 diabetes. Tight control is difficult to achieve and maintain, but its advantages are huge."
While the study looked at the effects of blood sugar control exclusively on type 1 diabetes, researchers say the benefits likely extend to people with type 2 diabetes as well. Type 2 diabetes occurs when the body becomes resistant to the effects of the insulin it produces or the pancreas isn't able to produce enough insulin to regulate blood sugar.
"There is a strong and growing body of evidence that everyone with diabetes gains from strict blood glucose control," said Dr. Catherine Cowie, who oversaw the follow-up study for the US National Institute of Diabetes and Digestive and Kidney Diseases.
"The take-home message is that good glucose control should be started as early as possible to delay or prevent serious diabetes-related complications," added Dr. Alan D. Cherrington, president of the ADA.