Although you can't change your family, you can modify many lifestyle-related risk factors for heart disease. 'You can keep your blood pressure and cholesterol and blood sugar under control. You can maintain a healthy weight, you can get regular exercise, and if you smoke, you can quit.'

Risks for heart disease include family history of the condition, age, high blood pressure, high cholesterol, overweight, current or former smoking, physical inactivity and diabetes.

Having a parent or sibling with heart disease has long been known to increase risk. But this new study, published in the Dec. 28 issue of the Journal of the American Medical Association, shows that having a brother or sister with heart disease is a significant independent risk factor.

"We studied 2,475 participants of the Framingham Offspring Study," said lead author Dr. Joanne M. Murabito, clinic director of the Framingham Heart Study.

Over eight years, Murabito's team compared the occurrence of heart disease in people with and without siblings.

"We found that participants who had a brother or sister with cardiovascular disease had higher levels of risk factors compared with participants who had a sibling without the disease," Murabito said. "In addition, participants with a brother or sister with cardiovascular disease had a 45 percent increased risk for the disease."

Genetic Factors

The increased risk appears to be attributable to a combination of genetics and childhood environmental exposures, the study found.

"Certainly, genetic factors that are shared from parents to offspring play a role," said co-author Dr. Christopher O'Donnell, associate director of the Framingham Heart Study, and co-chairman of its Genetic Steering Committee.

"In addition, exposures during childhood may be playing a role," O'Donnell said. "There is something shared by siblings that is unique in conferring risk."

Given these findings, Murabito believes that people should know if their siblings have heart disease and be aware that their own risk could be increased. "It is important for physicians to collect family history medical information," she said. "It is important to consider sibling cardiovascular disease history when looking at people with elevated levels of risk factors."

Although you can't change your family, you can modify many lifestyle-related risk factors for heart disease, Murabito said. "You can keep your blood pressure and cholesterol and blood sugar under control. You can maintain a healthy weight, you can get regular exercise, and if you smoke, you can quit."

Behavioral Traits

Dr. Roger S. Blumenthal, director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, said, "This study confirms what we have shown in studies at Johns Hopkins. "The main reason this happens is that siblings share common behavioral traits growing up."

This research highlights the importance of doctors taking a complete medical history, Blumenthal said.

"If you have a brother or sister or parent with early heart disease and you're middle-aged, you should remind your doctor about your family history and perhaps consider some other testing, such as a stress test, or a C-reactive protein blood test, or a coronary calcium scan," he said.

Another expert thinks that while the finding is important, the actual risk of developing heart disease if your brother or sister has heart disease is still small.

"Over eight years, there was only a 2 percent difference between heart disease among siblings with and without heart disease," said Dr. Harlan M. Krumholz, a professor of cardiology at Yale University Medical School. "That means that for every 50 people who have a sibling with heart disease compared with 50 people without -- over an eight-year period, there is one extra event."

There is some extra risk, Krumholz said, "but it's not like just because your sibling has heart disease that you're going to have heart disease. However, the knowledge that your sibling has heart disease can be an alert for you to pay close attention to your risk factors."

More information: The American Heart Association can tell you more about preventing heart disease.