"We teased out the relative effects of family history of stroke and family history of heart attack in the same population, so that we can directly compare the effects," says researcher Amitava Banerjee, PhD, MPH, a clinical lecturer at the University of Birmingham, U.K.
"Heart attacks are more heritable than stroke," he says. "That means a history of heart attack in your family is more strongly associated with your [risk of] heart attack than a family history of stroke [is associated with your risk of stroke]."
The findings are based on 1,921 patients. They had suffered either a stroke or other brain-related problem or a heart attack.
The study is published in Circulation: Cardiovascular Genetics.
Family History of Heart Attacks vs. Strokes
Researchers have tended to lump together stroke and heart attacks when studying family history, Banerjee tells WebMD.
He wanted to look at them separately to better understand how genetics might predict risk of each. Other research had suggested genetic differences in heart attack and stroke risk.
The researchers had found previously that the genetics of high blood pressure, for instance, is tied to stroke risk more than heart attack risk.
The men and women in the study were part of the ongoing Oxford Vascular Study. It began in 2002 to study strokes, heart attacks, and other vascular problems.
It includes more than 91,000 people in the U.K., served by a single hospital.
For this study, Banerjee's group evaluated 906 men and women who had heart attacks or other heart problems and 1,015 men and women who had strokes or 'mini' strokes, called transient ischemic attacks (TIAs).
The average age of the heart patients was 70; the average age of the stroke patients was 73.
Banerjee looked at the medical information to see if the parents of the patients had had strokes or heart attacks. They looked to see if the patients' brothers or sisters had strokes or heart attacks.
In both cases, family history more strongly predicted heart attack than stroke in the siblings.
"People with heart attacks who had one parent with heart attack were 1.5 times more likely to have a sibling with heart attack than a heart attack patient who had no family history," Banerjee tells WebMD.
"Heart attack patients who had both parents with a heart attack history were nearly six times as likely to have a sibling with a heart attack as heart attack patients without a family history," he says.
"Family history of stroke didn't work in this way," he says.
However, he says, family history of stroke increases the risk of stroke, but the link is not as strong as for heart attack.
He also found a ''clustering" effect for heart attack risk. "The more patients and siblings [within a family] are affected, the greater the risk," he says. That did not hold for stroke risk.
Exactly why a family history of heart attack seems to carry more risk is not known for sure, Banerjee says.
He speculates that it could be due to genetic influences. It could also be due to the interaction of genes and environment or early life environmental factors.
Advice Remains Same: Exercise, Eat Right, Don't Smoke
The findings are intriguing, says Ralph Sacco, MD, chair of neurology at the University of Miami Miller School of Medicine and immediate past president of the American Heart Association. He reviewed the findings for WebMD.
However, the overall population from the Oxford study is 94% white. So he says it is unclear whether the findings would apply to U.S. Hispanics and African-Americans.
The findings seem to confirm what some have thought all along, he says, ''that heart disease may be a little bit more linked to heredity than stroke."
Sacco suspects this may be because stroke can originate from a variety of causes. For instance, some are triggered by hardening of the arteries. The irregular heartbeat called atrial fibrillation can also lead to stroke.
The finding does not change lifestyle advice, Sacco says.
It is also important, he says, to remember that genetics is not the whole story. "Both stroke and heart attack are still under a lot of environmental and behavioral control," he says.