Having a sibling with heart disease is a strong risk factor for the illness, researchers said on Tuesday, although it is unknown whether the cause is shared genes or similar childhood diets.
Researchers concluded that having a sibling with heart disease conferred a 45 percent higher risk of a heart attack, stroke, or blood clot in the leg compared to people whose brothers or sisters were free of the illness.
"We were surprised that sibling cardiovascular heart disease may actually be a stronger risk factor than parental cardiovascular disease," said lead author Dr. Joanne Murabito of the Framingham Heart Study.
"It's unclear whether an early shared environment may be contributing," Murabito said. "Early dietary patterns and exercise patterns in childhood when siblings are living in the same household may account for some of our findings.
The Framingham Heart Study has collected 50 years worth of data on residents of the Massachusetts city of Framingham in an effort to combat heart disease.
The researchers followed 2,500 subjects for eight years who were free of heart disease at the start but who had brothers or sisters with the illness.
Writing in the Journal of the American Medical Association, Murabito said the findings could become more relevant as the genetic basis for diseases is better understood.
In the meantime, she urged people who have siblings with heart disease to be careful with their diets, to exercise regularly and to control their blood pressure.
