Scientists at Johns Hopkins University found that regardless of factors such as age or lifestyle, if any sibling - brother or sister - suffered a heart condition, the chances that a healthy brother will develop same condition increases by 20 percent within 10 years.
Same risk for a sister is lower at seven percent.
The study looked at data gathered from a larger study, involving 800 siblings between ages 30 to 60, conducted from 1983 to 2006. The participants come from nearly 350 families around Baltimore and were generally healthy but all had at least one sibling with premature heart condition that had required hospitalization. Half of the participants were women.
The results showed that the younger the age of the sibling who first develops heart disease, the greater the risk that arteries of other brothers and sisters will also narrow, harden and clog.
According to Science Daily, Study senior lead Diane Becker said: "The risk was greater than previously thought and makes clear the existence of a substantial, if uneven hereditary link in heart disease among brothers and sisters."
"In the meantime, brothers and sisters in families with a history of heart disease really need to monitor their health more closely and in consultation with their physician, and consider if drug therapy and better diet, exercise and lifestyle habits are needed."
Her colleague, Dhananjay "Jay" Vaidya, added: "Knowing that your brother or sister had a heart attack, or that a sibling suffered chest pain and was rushed to a hospital stand out as possibly the most important predictor of whether or not another sibling develops blocked arteries."
Although the scientists agree genetic factors are to be blamed, they are unclear exactly how.
The team is working on the next stage of identifying genes linked to sibling risk so that they can develop a blood test which would alert families at risk long before symptoms are manifested.
The findings are published in November issue of the American Journal of Cardiology.
