But a landmark study shows that by keeping their blood sugar under tight control, people with type 1 diabetes can reduce their risk of heart attack, stroke, and death from heart disease by 57%. Saul Genuth, MD, of Case Western Reserve University, chaired the study.
"We see a greater reduction in [heart attack, stroke, and death] from intensive blood glucose control than from drugs that lower blood pressure and cholesterol," Genuth says, in a news release. "This therapy should begin as early as possible and be maintained as long as possible."
It's likely that tight blood-sugar control will help people with type 2 diabetes, too. But proof that the benefits outweigh the risks won't arrive until a study of such patients is finished in 2009. Nevertheless, the current report -- in the Dec. 22 issue of the New England Journal of Medicine -- powerfully links high blood sugar to heart disease.
Beginning in 1983, Genuth and colleagues signed up 1,441 type 1 diabetes patients. Half were assigned to what then was normal treatment: daily blood or urine testing for sugar levels, and one or two insulin shots a day.
The other half of patients got intensive treatment. They checked their blood-sugar levels at least four times a day, and took insulin injections three or more times a day or used an insulin pump. Their goal was to keep their HbA1c level -- a measure of average blood sugar over the past two to three months -- at less than 6%.
Over the 6.5-year study, the intensive-treatment group averaged an HbA1c level of 7.4%, while the normal-treatment group averaged 9.1%.
When the first phase of the study ended in 1993, normal-treatment patients were offered intensive treatment. Over the next decade, their HbA1c levels dropped. During that same time, the average HbA1c level for the original intensive-treatment group went up. Soon, both groups had the same HbA1c level.
Nevertheless, the effects of intensive treatment lingered. Even though the original intensive treatment group let their HbA1c levels rise well above the level of 7% recommended by the American Diabetes Association, they still had half the heart risk of the original normal-treatment group.
"One can only imagine what the reduction in the risk of [heart] disease events would have been had the intensively treated group ... had a greater difference in [blood-sugar] control," writes LSU researcher William t. Cefalu, MD, in an editorial accompanying the study.
Cefalu says he wonders whether it is time to lower the blood-sugar targets for children and adolescents as well as for adults. However, he notes that tight control is very hard to achieve.
"The medical community needs better means, different strategies, and a different mindset if we hope to improve and maintain [blood-sugar] control in patients with type 1 diabetes and minimize side effects," he writes. "Until the latter issue is addressed by the availability of new therapies and innovative approaches, the translation of research findings from a landmark study such as [this trial] may not alter clinical practice for many years. Given the complications and mortality attributed to cardiovascular disease among patients with type 1 diabetes, this delay would be most unfortunate."