The study, conducted by Dhananjay 'Jay' Vaidya, M.B.B.S., Ph.D., an assistant professor at Hopkins, who was also an alumni of the Armed Forces Medical College, Pune, India, senior study investigator Diane Becker, M.P.H., Sc.D and colleagues found that regardless of age or lifestyle factors, if any sibling, brother or sister, suffered a heart attack, or chest pain from blocked arteries, the chances of any healthy brother developing similar problems rises within 10 years by 20 percent.
For sisters, the risk was less but still evident, at 7 percent.
"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, which can lead to a fatal heart attack," Vaidya said.
For the study, the researchers used information from earlier study, which involved monitoring in 800 siblings in the age group of 30-60 years.
The study participants, in which half were women, came from nearly 350 families and were generally healthy. But all had at least one sibling with premature coronary heart disease that had required hospitalisation.
In these families, the team found that siblings who were obese or overweight had a 60 percent increased risk of suffering a serious heart ailment, such as a heart attack, before the age of 60 years.
At the beginning of the study blood tests and physical exams were conducted to assess each individual's risk factors.
Researchers further added that the younger the age of the sibling who first developed heart disease, the greater the risk that other brothers' and sisters' arteries would also narrow, harden and clog.
"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," Becker said.
She also added that a genetic blood test to assess sibling risk in families with a history of heart disease could reduce that risk by encouraging earlier lifestyle and drug interventions.
"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," Becker added.
Vaidya suggested that genes could make these people more susceptible to known disease risk factors, or that genes could make people more vulnerable to some as-yet-unknown risk factor.
"Genetic factors are clearly to blame, although just how that works is unclear," he said.
The study will be published in the American Journal of Cardiology.