The findings show that good health habits should be a key part of prevention efforts, even in people with a family history of early heart disease, researchers said.
The study included 1,075 people under age 50. Of those, 555 had coronary artery disease.
The investigators assessed five lifestyle factors linked to heart disease: physical inactivity, smoking, high blood pressure, diabetes and high cholesterol.
In all, 73% of patients had at least three of the risk factors compared to 31% of those without coronary artery disease (the control group).
In both groups, the odds of coronary artery disease increased with each additional risk factor. The risk was three times higher for those with a single risk factor and 24 times higher for those with three or more, the findings showed.
The researchers also found that the patients with coronary artery disease had a higher average genetic risk, based on 33 factors.
While their overall score on those 33 factors was an independent predictor for premature heart disease, the influence of genetics declined as the number of modifiable lifestyle factors increased, according to the study presented Monday at a meeting of the European Society of Cardiology (ESC), in Paris.
Research presented at meetings is typically considered preliminary until published in a peer-reviewed journal.
"Genetics are an important contributor to premature heart disease but should not be used as an excuse to say it is inevitable," study author Dr. Joao Sousa said in an ESC news release. Sousa is a cardiologist at Funchal Central Hospital in Portugal.
"In our clinical practice, we often hear young patients with premature heart disease 'seek shelter' and explanations in their genetics/family history," he noted. "However, when we look at the data in our study, these young patients were frequently smokers, physically inactive, with high cholesterol levels and high blood pressure - all of which can be changed."
Sousa said the study provides strong evidence that people with a family history of early heart disease should embrace a healthy lifestyle. "That means quit smoking, exercise regularly, eat a healthy diet, and get blood pressure and cholesterol levels checked," he concluded.