Strength training may cause enlarged aortas in NFL linemen
March 22, 2017
That’s what I worked to find out, along with a group of fellow doctors from UT Southwestern, Cleveland Clinic and MedStar Sports Medicine in Baltimore. Our research indicates that retired NFL athletes are more likely to have enlarged aortas than people in the general population. Enlarged aortas are linked to several dangerous heart conditions. We presented our results during two sessions at the 2017 American College of Cardiology’s 66th Annual Scientific Session & Expo.
The origins of our studyBeginning in the early 2000s, we recruited Dallas County residents to take part in our Dallas Heart Study — one of the largest cohort studies for heart disease in the country. A cohort study involves monitoring a group of people over a long period to see how many of the participants develop diseases. Looking back, we can determine what risk factors contributed to the disease and gain a better understanding of why certain diseases occur. Researchers nationwide use data from the Dallas Heart Study to help drive research into heart and vascular problems.
One example of such research was conducted by a group of doctors who have worked with the NFL to conduct screening fairs for retired players who may be at risk for heart and vascular disease. These fairs, coordinated by MedStar Sports Medicine in Baltimore, took place in 10 major American cities, including Dallas, between 2014 and 2015.
Simultaneously, a Cleveland Clinic researcher began noticing that many former strength-training athletes’ aortas were larger than those in the general population. The aorta is the largest artery, and it carries blood out of the heart as it flows to the rest of the body. He wanted to find a dataset of large, elite former athletes to look into this question more systematically, which led to partnering with the NFL study. The Cleveland Clinic team collaborated with us so we could compare data from the former NFL players with data from the Dallas Heart Study participants to determine whether this risk was real and ascertain what it could mean.
The dangers of an enlarged aortaThe aorta has several segments that can become enlarged. Our study focused on the ascending aorta, which carries blood up and out of the heart before the aorta turns downward toward the belly. The size of a person’s aorta can vary depending on sex, age, and physical activity, but typically, it is less than 3.5 centimeters (about 1.38 inches) in diameter.
Generally, we start to get concerned when an aorta is greater than 4 centimeters in diameter. People with larger aortas tend to be at increased risk for an aortic aneurysm formation. This is when the widened aorta bulges because it’s been weakened. This bulge can lead to a tear of the inner lining of the aortic wall, known as aortic dissection. It also can tear completely, which is an aortic rupture. Both of these are extremely dangerous and can be fatal without treatment.
What we found in our studyOur main goal was to determine whether retired NFL players really do have aortas that are larger than those of people in the general population. Generally, the bigger you are physically, the bigger your aorta. So we compared NFL players with Dallas Heart Study participants who were around the players’ average height and weight. We included men who were 40 or older with a body mass index (a combination of height and weight) of greater than 20.
While the former NFL players were only slightly larger on average than the comparison group from the Dallas Heart Study, we found that nearly 30 percent of the retired NFL players had aortas that were larger than 4 centimeters, compared with less than 10 percent of the selected Dallas Heart Study participants. Even when we accounted for factors such as age, blood pressure, diabetes, smoking, cholesterol, and, most importantly, body size, we found that former NFL players were twice as likely to have an aorta size in the dangerous range relative to Dallas Heart Study participants – and the average retired NFL player’s aorta was nearly 12 percent bigger. That’s a significant difference.
Retired linemen – some of the biggest players in the game – were most likely to have enlarged aortas. In the NFL, the average offensive lineman is 6 feet 5 inches tall and weighs 312 pounds, while the average defensive lineman is about 6 feet 2 inches tall and weighs around 300 pounds. We found that retired players in our study who played other positions were less likely to have enlarged aortas.
We know certain kinds of intensive exercise can put stress on the aorta. That’s why a doctor who’s treating a patient with an enlarged aorta will often recommend that the patient not engage in certain types of exercise, such as heavy, intense weightlifting. What differentiates the retired NFL athletes is their intense, high-level strength training. This sort of strength training may lead to the changes we observed in their aortas.
And these sorts of workouts aren’t limited to football players. Enlarged aortas could be a concern for other athletes who do a lot of high-level strength training, such as:
What we don’t know yetOne key point I want to emphasize is that we don’t know if this means retired NFL players are at greater risk for heart disease or other complications we normally associate with large aortas. An enlarged aorta from strength training or large body size might not be as risky for complications as those who have enlarged aortas from other reasons.
In another part of our study, we measured the amount of coronary calcium in the retired players and compared it to a similar group of people from the Dallas Heart Study. Coronary calcium is the amount of calcium in the heart arteries, which is deposited from arterial plaque buildup. It’s a strong predictor of heart attack and stroke risk.
But the retired NFL players were on par with what we saw in the general population. And they had no great difference in their 10-year atherosclerotic cardiovascular disease (ASCVD) scores, or their overall risks of heart attacks or strokes within the next 10 years.
We need to investigate whether having an enlarged aorta means the same thing for a retired elite athlete as it does for someone in the general population. Because the retired NFL players haven’t yet been followed for long periods of time, we don’t know if they’re at greater risk for complications or if they’re more likely to need surgery to repair their aortas.
We also need further study into when this might develop in strength-training athletes. Is it only an issue for those who compete at the professional level? Could this be a problem for college football players who don’t go on to play in the NFL? Or even high school athletes who don’t play in college?
The next logical step is to study whether this increased risk of enlarged aortas among retired NFL players translates into an increased risk for aneurysms, aortic ruptures, or other conditions.
Do doctors need to be more aggressive in screening these athletes? Do we need to treat them sooner? I hope future research can provide the answers.
UT Southwestern researchers involved in this study include Colby Ayers, M.S., Department of Clinical Sciences; David Carruthers, M.D., Department of Internal Medicine; Christopher Maroules, M.D., Department of Radiology; James de Lemos, M.D., Department of Internal Medicine, Cardiology; and Parag Joshi, M.D., Department of Internal Medicine, Cardiology.