High blood sugar readings have been tied to a greater risk for heart disease. While these blood sugar readings may signal risk of pre-diabetes or diabetes, they may not be a sign that heart disease waits ahead.
Heart disease and stroke are the leading causes of death and disability among people with type 2 diabetes, according to the American Heart Association. Some medical experts have concluded that taking into account elevated blood sugar (glucose) levels — measured by hemoglobin A1c (HbA1c) — may predict heart disease.
A large, new study, however, found that information on HbA1c added little value to a traditional heart health assessment that used conventional risk factors such as smoking, cholesterol levels and blood pressure.
Emanuele Di Angelantonio, MD, of the Department of Public Health and Primary Care at the University of Cambridge in England, and colleagues reviewed details from 73 scientific investigations, representing 294,9989 patients.
All participants had no known history of diabetes or cardiovascular disease at the start of each study.
At a median follow-up point of about 10 years, scientists recorded 13,237 incidents of heart disease and 7,603 strokes.
The researchers weighed the likelihood of a person developing heart disease based on standard risk factors such as cholesterol levels, smoking and blood pressure. When they added in details on HbA1c levels, they noted little increased benefit for predicting cardiovascular risk.
These results have gone against some previous medical opinions regarding HbA1c as a risk assessment tool. The 2010 American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines stated that HbA1c readings could help determine heart disease risk in patients without diabetes. The Canadian Cardiovascular Society issued as similar opinion in 2012.
"Physicians are always looking for a better way to predict who will develop heart disease," Sarah Samaan, MD, cardiologist and physician partner at the Baylor Heart Hospital in Plano, Texas, said to dailyRx News.
"One such indicator that has seemed to hold promise is hemoglobin A1C. This test is usually used to help decide whether a person may be diabetic, as well as whether someone who is diabetic has their blood sugar under good control. There is a fairly wide range that is considered to be normal, and the researchers wanted to know if those who were at the higher end of normal were at greater risk," Dr. Samaan explained.
"It's important to realize that this study did not look at diabetics, but instead focused on people without diabetes. Diabetes itself is a major risk factor for heart disease. After reviewing the results of thousands of individuals, the verdict was that adding hemoglobin A1C to the traditional heart disease risk factors did not help much in sorting out who would and who wouldn't develop heart disease over time. Age, blood pressure, cholesterol, and whether or not you smoke are much more reliable indicators of who is and is not at higher risk for heart attack and stroke," Dr. Samaan said.
Dr. Di Angelantonio told dailyRx News, “Previous research was based on a limited number of studies and failed to take into account specific measures of risk prediction. This research was able to do that in a large number of studies, and showed that adding information on glycemia (blood sugar) measures provide limited additional clinical information to predict who will develop cardiovascular disease.”
The American Heart Association says that traditional risk factors for heart disease are high LDL (“bad”) cholesterol, low HDL (“good”) cholesterol, high blood pressure, family history, diabetes, smoking, obesity and increasing age. While some risk factors such as family history and age cannot be changed, others can be modified. Diet and exercise, for example, can improve blood pressure, obesity and cholesterol levels.
This study was published in the March 26 issue of the Journal of the American Medical Association (JAMA). The study was funded by the British Heart Foundation, the UK Medical Research Council, the UK National Institute of Health Research and the Cambridge Biomedical Research Research Centre.