Strict Blood Sugar Control Lowers Heart Risks in Diabetics

THURSDAY May 21, 2009 --Diabetics who strictly control their blood sugar levels also reduce their risk of heart attack and cardiovascular disease, British researchers report.

There have been several conflicting reports about the value of dramatically reducing blood sugar levels in diabetic patients in preventing heart attack and heart disease. In fact, some have suggested that significantly lower blood sugar levels could possibly be harmful.

"We show that if you lower glucose measures by something called HbA1c by 0.9 percent over five years, you reduce heart attacks by 17 percent and fatal and nonfatal heart attacks by 15 percent," said lead researcher Dr. Kausik Ray, a senior clinical research associate from the University of Cambridge. "There is no excess risk of death in contrast to earlier claims."

The implications are enormous, Ray said. "There have been claims recently by doctors that lowering glucose to less than 7 percent could be harmful. We disprove that in the largest study to date," he said.

On average, diabetics die seven years earlier, and they need multiple interventions such as lowering blood pressure and cholesterol to reduce their risk of dying. "Despite this, the risk remains high, so better control of sugars further reduces residual risk," Ray said.

The report is published in the May 23 issue of The Lancet.

For the study, Ray's team analyzed data from five studies that included 33,040 patients. Among all these patients, there were 1,497 heart attacks, 2,318 cases of coronary heart disease, 1,127 strokes and 2,892 people died.

The researchers noted hemoglobin A1c concentrations (HbA1c) in the patients. More intensive blood sugar control was achieved when patients used additional medications and/or higher doses to get lower HbA1c levels.

HbA1c indicates the average blood sugar concentration for the preceding two to three months. In general, healthy people who do not have diabetes have HbA1c levels ranging from 4 percent to 5.9 percent, while patients with diabetes usually have HbA1c levels over 6.5 percent, the researchers noted.

Among people who received intensive treatment to control their blood sugar, their HbA1c was 0.9 percent lower than patients receiving standard treatment (6.6 percent vs. 7.5 percent).

Those whose blood sugar was strictly controlled saw a 17 percent reduction in non-fatal heart attacks, and a 15 percent reduction in events associated with heart disease, the researchers found.

"Better control of blood sugars reduces risk of heart attacks and heart disease," Ray said. "Treatment should be tailored to individual needs, however."

Dr. Theodore Mazzone, chief of the Section of Endocrinology, Diabetes and Metabolism at the University of Illinois at Chicago and author of an accompanying journal commentary, noted there have been trials that failed to show that controlling blood sugar reduced heart attacks.

"People with type 2 diabetes are at greatly increased risk for heart attack," Mazzone said. "We do know that treating them with statins and controlling their blood pressure can have a significantly beneficial effect for reducing this risk, but even after that, there still is residual incremental risk compared to non-diabetic patients," he said.

Taken together, the trials analyzed in this study do show a benefit in preventing heart attacks from blood sugar control, Mazzone said. "It would be premature for doctors or patients to completely discard glucose control as a strategy for managing heart attack risk in patients with diabetes," he said.

Glucose control is not as important as lowering cholesterol and blood pressure in preventing heart attacks among diabetics, Mazzone said. "The effect of glucose is going to be smaller," he said.

Adding even the small benefit for heart attack is worthwhile, because it adds to the overall benefit of glucose control in these patients, Mazzone said. It's already well established and well accepted that glucose control can minimize the risk for blindness, minimize the risk for kidney disease, minimize the risk for nerve disease.

In another report in the same journal issue, Dr. David Williams, from the Institute for Women's Health at University College London, and colleagues looked at 20 studies and found that pregnant women who develop gestational diabetes have a seven-and-a-half times increased risk of developing type 2 diabetes after giving birth.

"The increased risk in relative risk of type 2 diabetes reported in this meta-analysis might help motivate mothers to attend screening programs, and health-care professionals to increase uptake to these programs or perhaps suggest the best time for reassessment. Since the risk of type 2 diabetes seems to be maintained for several years, consideration of whether any form of continuous assessment would lead to health gains is important," the authors noted.

More information

For more on diabetes and heart disease, visit the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.

Posted: May 2009


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