Cleveland Clinic researchers found that a group of retired National Football League (NFL) players have significantly larger aortas when compared to men in the general population. The clinical significance of these findings is unknown and will require further evaluation, researchers said, though enlarged aortas are a known risk factor for life-threatening aortic dissections or aortic ruptures.

The study published in the journal Circulation: Cardiovascular Imaging found that a group of 206 retired NFL players were twice as likely to have a dilated ascending aorta compared to a control group. The study compared a self-selected sample of former NFL athletes to a presumed non-elite athletic control group from the Dallas Heart Study-2.

When comparing the two groups, the retired NFL players had lower levels of hypertension, lower levels of high cholesterol and fewer smokers, all of which are risk factors for the development of an enlarged aorta. The average age was 57.1 for retired players and 53.6 for the Dallas group, with a body mass index of 2.4 and 2.1 respectively. Still, despite fewer risk factors, retired NFL athletes had a significantly larger ascending aortas and were twice as likely to have larger ascending aortas as those men in the Dallas study.

“Although their aortas were bigger, they had a lower risk profile. We need to better understand what happens to these athletes’ bodies long-term,” said Dermot Phelan, MD, PhD, director of Cleveland Clinic’s sports cardiology center and senior author on the paper. “There isn’t anything to suggest that elite athletes are at higher risk of developing an aortic dissection later in life, but until we know more about what this means, we should be cautious and continue to monitor these folks on a regular basis.”

The aorta is the main blood vessel that carries blood from the heart throughout the body. The aorta has multiple sections and the section of the aorta that was studied is the ascending aorta, which carries blood from the heart to the head and neck before supplying the rest of the body. When the aorta becomes enlarged there is a risk for aortic dissection or aortic rupture, which is potentially a life-threating event.

The average retired NFL player’s aorta measured 38.5 +/- 5 mm compared to the control group who measured 34 +/- 4 mm; 40mm is used as an arbitrary cut-off in clinical practice to define a dilated ascending aorta. 29.6% of NFL athletes had an aorta measuring larger than 40mm versus the controlled group at 8.6%. After adjusting the data, based on several variables known to affect aortic size, the NFL players were twice as likely to have an enlarged aorta. The NFL players in the study were broken down into two groups—linemen (tackles, guards, centers, defensive tackles, defensive ends, or linebackers) and non-lineman (quarterbacks, running backs, wide receivers, tight ends, cornerbacks, safeties, kickers or punters). The study showed a trend toward linemen having larger aortas.

The cause of aortic enlargement in retired NFL players is not addressed in this study but the authors suggest that it may be related to the hemodynamic stress of repetitive strenuous exercise over many years.

Researchers outlined some of the study’s limitations: the findings are specific to a small select group of former NFL athletes with the potential for selection bias and which may not reflect the entire former NFL population. Given the relatively small number of former athletes involved, this data should be considered hypothesis-generating and will hopefully result in longer term studies in a wider population of athletes.

Study participants were selected from a group of 484 retired players who participated in a voluntary cardiovascular screening program run by the Cleveland Clinic under the auspices of the NFL Player Care Foundation Healthy Body and Mind Screening Program between January 2014 and January 2015. Players w