Early heart disease in a sibling is a better predictor of risk for coronary heart disease than parental history or traditional risk factor scoring, according to an article published online October 4th by Circulation. The results strongly suggest that physicians should pay close attention to patients who have a sibling with an early history of coronary heart disease and evaluate which, if any, clinical risk factors merit aggressive treatment.

“Family history has for years been recognized as a risk factor in predicting a person’s chance for developing coronary heart disease early on in life − separate from better-known risk factors, such as HDL and LDL cholesterol levels, blood pressure, smoking and age. But we never knew if there was a difference between sibling and parental histories of early heart disease in terms of a given individual’s risk of developing early atherosclerosis,” said the study’s senior author, Roger Blumenthal, MD. Blumenthal is also a spokesman for the American Heart Association.

“Our study shows that asymptomatic individuals with sibling history were more likely than those with just a parental history to develop early atherosclerosis, and thus closer monitoring is advised as well as earlier consideration of other therapies − such as aspirin, blood pressure, and cholesterol-lowering therapies − to slow development of atherosclerosis.”

In a cross-sectional study of nearly 8,500 American adults, one half older and the other half younger than age 52 years, and all with no previous signs of heart disease, the researchers found that siblings were 2.5 to 3.0 times more likely to have a higher degree of coronary atherosclerosis if a brother or sister had already been diagnosed with heart disease. Parental history was also associated with subclinical atherosclerosis, although to a lesser extent than sibling history. Gender differences among siblings or parents were not examined, so no conclusions could be drawn regarding specific male and female combinations.

For the study, a family history of heart disease meant that a sibling or parent experienced a fatal or non-fatal myocardial infarction or underwent some form of coronary revascularization, including bypass surgery, by age 55 years.

Using electron-beam tomography, a form of CT imaging that is often used in testing for heart disease, patients were scanned for early signs of atherosclerosis as measured by the presence and extent of coronary artery calcification. Study participants were graded for atherosclerosis − on a scale from low, to moderate, to high − by levels of calcification as seen by CT scan. Study participants with a sibling history were nearly 4 times more likely to have advanced levels of atherosclerosis when compared with people without any family history; on the other hand, participants with just a parental history were about 2 times more likely to have advanced levels of coronary calcium.

Signs of calcification and plaque build-up were observed in all groups, regardless of family history, but the burden was greatest among those patients who had a parental or sibling history of early heart disease, ranging from 36 percent to 78 percent, for both men and women. Other major risk factors for early heart disease − such as smoking, high cholesterol levels, high blood pressure, diabetes and obesity − were factored into the statistical analysis.

“These data support guidelines saying that more rigorous preventive measures should be undertaken in individuals with a history of premature heart disease,” said study lead author Khurram Nasir, M.D., MPH. “Preventive measures include cutting back on fatty foods, increasing exercise and, possibly, taking cholesterol-lowering medications. They also need to be initiated earlier if they are to have a meaningful effect. Twenty-five percent of the time, the first manifestation of coronary heart disease is sudden cardiac death. Noninvasive measures, such as electron beam tomography, to detect coronary artery calcification can be used to identify the presence of early atherosclerosis in people with a family history of premature coronary heart disease.”

“Our next goals are to explore the causal mechanisms, including specific genes and environmental risk factors, that explain the strong association between the familial clustering of individuals with early forms of heart disease, especially in siblings, and increased plaque burden in the coronaries. The other overall long-term goal, of course, is to use these findings to develop faster and better means of identifying early atherosclerosis in high-risk groups and prevent its progression to full-blown heart disease.”