By Stephanie Stahl

PHILADELPHIA (CBS) — Players in the National Football League are known to be big tough guys but new research from the Cleveland Clinic shows former players had significantly larger aortas, nearly 12 percent bigger, when compared to non-athletes.

“The surprising result of all of this was the actual overall average size of the aorta in the NFL group, which was really much bigger than we anticipated going into the study,” Dr. Dermot Phelan of the Cleveland Clinic.

Researchers reviewed heart scans of 206 retired NFL players with an average age of 56. The aorta is the main artery that supplies blood from the heart to the rest of the body.

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Previous studies have shown some athletes have larger hearts and thicker heart muscles as a result of high intensity exercise.

Typically, an enlarged aorta is a risk factor for developing a tear in the vessel wall, which can be life-threatening.

Former Philadelphia Eagles long snapper Jon Dorenbos had an aortic aneurysm, an enlargement of the aorta and needed immediate open heart surgery.

The new research did not look at any current NFL players and did not address whether the enlarged aortas are actually caused by playing professional football.

“Until we know more about what this means, we should be cautious and continue to monitor these folks more closely than we would normally,” Dr. Phelan said.

The research also found most of the former players didn’t smoke, didn’t have high cholesterol and/or blood pressure, which are usually found among people with enlarged aortas.