Blood Test May Better Predict Diabetics' Heart Risk: Study
MONDAY July 25, 2011 -- A standard test used to measure blood sugar levels in people with diabetes could also help predict their risk of cardiovascular disease, a new study suggests.
The test -- which measures levels of hemoglobin A1c (HbA1c) in blood -- enables doctors to assess how well their diabetic patients' blood sugar is controlled over several months. Diabetes is a known risk factor for cardiovascular disease, but the degree of risk may differ in individuals, the researchers explained.
"It is possible that identification of people with [type 2] diabetes who have a low estimated 10-year risk of cardiovascular disease may be useful in making treatment decisions," said lead researcher Nina P. Paynter, an associate epidemiologist at Brigham and Women's Hospital in Boston.
Usually, all diabetics are considered at high risk for cardiovascular disease and they are often treated aggressively with cholesterol-lowering drugs and blood pressure medications to help reduce the risk.
But many of them might be at substantially lower risk and not need such aggressive therapy, the authors said.
"Some people with diabetes have an estimated 10-year cardiovascular risk lower than 20 percent, especially in populations with a low overall risk of cardiovascular disease," Paynter said.
The report was published online July 25 in the Archives of Internal Medicine.
For the study, Paynter's team collected data on 24,674 women and 11,280 men who took part in the Women's Health Study and the Physician's Health Study II.
Both studies collected data on the participants' HbA1c levels. The men were followed for a median of 11.8 years and the women for 10.2 years, the researchers noted.
Over that period, 125 of the 685 women with type 2 diabetes had a heart attack or stroke as did 170 of the 563 diabetic men. Among participants without diabetes, 1,382 men and 666 women had cardiovascular events, the researchers reported.
By adding HbA1c test results to the patient data, which also included levels of cholesterol and C-reactive protein, the researchers said they were able to more accurately predict the risk of cardiovascular disease in the diabetic patients.
They found that 71.9 percent of diabetic women had less than a 20 percent risk of cardiovascular disease over 10 years, while only 24.5 percent of the men had a similarly low risk.
This difference may be partly explained by the increased risk for cardiovascular disease that accompanies age, and the delayed risk in women, the researchers said.
Noting further research is needed to confirm the findings, they noted the prediction improvement was better in low-risk groups.
Paynter also said the test might help people without diabetes evaluate their cardiovascular risk.
Dr. Mark J. Pletcher, an associate professor of epidemiology at the University of California, San Francisco, and author of an accompanying journal editorial, doesn't think predicting individual risk of cardiovascular disease will change current treatment of diabetic patients.
"Even though the risk estimation may be more accurate, it still may be a better decision to put them on cholesterol-lowering drugs, because of long-term risk of heart disease," he said.
Pletcher said in his own clinical practice he will continue to treat diabetics aggressively.
"Risk prediction for risk prediction's sake is not really that useful an exercise," Pletcher said. "It's only useful if it informs a clinical decision. And when you are not going to change a decision, as I don't think I will, then I don't think it's worth that much to refine risk estimation."
For more information on diabetes, visit the U.S. National Library of Medicine.
Posted: July 2011