Family history of premature heart disease has long been considered a risk factor for heart problems in future generations. The new study, of four million Danish citizens followed for three decades, strengthens the evidence.

Researchers found people with a parent or sibling who died young of heart problems were roughly twice as likely as others to be diagnosed with coronary heart disease - where "plaques" build up in the heart arteries, raising the risk of heart attack - before age 50.

They also had double the risk of suffering a ventricular arrhythmia - an often fatal rhythm disturbance in the heart's main pumping chamber.

None of that means genes are heart disease destiny, noted Dr. Amit Khera, a preventive cardiologist who was not involved in the research.

"Just because you're at elevated risk does not mean you're going to have a heart attack," said Khera, who directs the preventative cardiology program at the University of Texas Southwestern Medical Center in Dallas.

But, he said, the findings underscore the importance of knowing your family history - starting at a young age.

That way, Khera noted, you can make healthy lifestyle changes and talk to your doctor about any screenings you should have, like regular blood pressure and cholesterol checks.

For the study, researchers at the Statens Serum Institut in Copenhagen combed through public health data on almost four million Danish citizens born after 1949.

Between 1978 and 2008, almost 130,000 of them were diagnosed with some form of cardiovascular disease before age 50.

Those odds were heightened when a first-degree relative had died of heart problems before hitting 60, the researchers report in the Journal of the American College of Cardiology.

But those risks were also elevated when a second-degree relative - a grandparent or half-sibling - had died young. The risk of coronary heart disease, for example, was 43 percent higher in people with one second-degree relative who had died before age 60.

"This study tells us that a grandparent's history is meaningful, too," Khera said.

And the more relatives who died young, the greater the risks. When two or more first-degree relatives had died of heart ills before age 60, a person's own risk of early heart disease rose five-fold.

"As with other chronic diseases, people should try to find out what they can about their family history," Dr. Mattis Flyvholm Ranthe, the lead researcher on the study, said in an email.

Both Ranthe and Khera said doctors should try to dig deeper into patients' family histories.

But if your doctor has not done that, Khera noted, you can still find out if any relatives died young - of heart disease or unknown causes - and bring it up to your doctor yourself.

You cannot, of course, change your genes to lower your heart risks. But you can alter your lifestyle - by not smoking, getting regular exercise and eating a healthy diet, for example.

"Know that there is something you can do about it," Khera said.

It's not fully clear how much of a difference lifestyle changes or medication for high blood pressure or cholesterol can make for people with heart disease in their family. But it's known that those steps help curb heart risks in general, Khera pointed out.

"There's no reason to suspect that preventive measures wouldn't apply to these folks as well," he said.

SOURCE: bit.ly/PEP18s Journal of the American College of Cardiology, online August 20, 2012.

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