Heart benefits of good diabetes control may last for decades

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Six-and-a-half years of intensive diabetes control may protect against heart attack and stroke for the next 30 years, according to long-term results from a U.S. trial that began in the 1980s.

Participants in the Diabetes Control and Complications Trial (DCCT) who strictly controlled blood sugar after being diagnosed with type 1 diabetes had over 30 percent lower rates of heart disease, heart attacks and strokes over the next three decades compared to those who got standard care in those early years.

"Efforts to make intensive diabetes management attainable at a young age must continue so as to reduce the rates of life-threatening cardiovascular disease over the life span for patients with diabetes," the study authors conclude in the journal Diabetes Care.

Starting with good blood sugar control after being diagnosed with type 1 diabetes helps to reduce the likelihood of diabetic complications like blindness and kidney disease.

The DCCT ran from 1983 to 1993, and involved 1,441 volunteers with type 1 diabetes, ages 13 to 39 years old, as well as 29 medical centers in the United States and Canada.

Past studies have shown that in the first 10 years, early intensive diabetes therapy significantly reduced the risk of developing cardiovascular disease (heart attack, stroke, cardiovascular death, angina and the need for coronary artery disease treatment).

Now, Dr. Rose Gubitosi-Klug from Case-Western Reserve University in Cleveland, Ohio, and colleagues report the results over two decades after the trial concluded, when more than 1,300 patients no longer had their blood sugar management dictated by the study protocol.

While blood sugar levels were better for the intensive therapy group during the study, there were only trivial differences in blood sugar control in the ensuing years between those who originally had intensive diabetes therapy and those who had the standard diabetes therapy of the time.

Yet, after an average of 26 years, the risk of having any cardiovascular event was 30 percent lower in the patients who originally received intensive diabetes therapy, despite this lack of difference in blood sugar control in the later years.

The risk of a first nonfatal heart attack, stroke or cardiovascular death was 32 percent lower with intensive, versus conventional, therapy.

Blood sugar control in the later years mattered, too - each 10 percent improvement in control (measured by hemoglobin A1C) was associated with a 17 percent reduction in the risk of a cardiovascular event.

Gubitosi-Klug did not respond to a request for comments.

Dr. John B. Buse, a diabetes expert from University of North Carolina School of Medicine in Chapel Hill, told Reuters Health, "Though we were hopeful that intensive management of diabetes would be associated with sustained benefits, I do not think anyone believed that the benefits would be sustained over 30 years of follow-up in the DCCT. It suggests that there is great value to improved glycemic control for whatever period of time that it can be sustained."

Even so, he said by email, "The one remaining but unanswerable question is: Does this comparison of intensive management in the 1980's and 1990's, as compared to what today would be viewed as totally inadequate care, really predict the benefit of improved control though best practices in 2016 as compared to less good practices today?"

Buse thinks it's "best to assume that the answer is 'yes' and that targeting near normal blood glucose levels and accepting an A1C of ~7 percent should be the aim of diabetes care today."

Dr. Rozalina G. McCoy, another proponent of intensive diabetes therapy from Mayo Clinic in Rochester, Minnesota, said, "For me, as a practicing primary care physician and endocrinologist, this study reinforces the importance of starting patients with type 1 diabetes on treatment early and utilizing every possible resource to help patients and their families manage their diabetes in a way that not only achieves and maintains glycemic targets, but is also sustainable by being affordable and tolerable (e.g., with least possible hypoglycemia and burden of treatment)."

The study results "will help me engage patients and families in informed and shared decision-making by showing them that there truly is benefit to reducing hemoglobin A1C," she told Reuters Health in an email.