Atrial Fibrillation Prevalence Is Markedly Increased in NFL Retirees

Study raises prospect of upper limit of exercise where maladaptive heart effects kick in

Atrial Fibrillation Prevalence Is Markedly Increased in NFL Retirees

As scrutiny mounts around football’s effects on long-term brain health, a new study demonstrates that heart health — specifically the risk of atrial fibrillation (AF) and conduction system abnormalities — among retired National Football League (NFL) players deserves increased vigilance too.

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The study is a cross-sectional investigation comparing 460 middle-aged NFL retirees (mean age, 56 ± 12 years) with an age- and race-matched control group of 925 nonathlete males from the population-based Dallas Heart Study.

It found that AF was present at a tenfold higher rate — 5.0 percent versus 0.5 percent — among the NFL retirees compared with the controls. After multivariable regression analysis, the former NFL athletes still had an odds ratio for prevalent AF of 5.5 (95% CI, 2.0-15.4).

In addition, the former NFL athletes had…

  • A tenfold higher prevalence of pacemaker implantation (2.0 percent vs. 0.2 percent; P < .01)
  • Lower resting heart rate (60 ± 8 bpm vs. 67 ± 9 bpm; P < .01)
  • Higher prevalence of first-degree atrioventricular block (18 ± 6 percent vs. 8 ± 4 percent; P < .01)
  • Longer mean QRS interval (96 ± 17 ms vs. 93 ± 13 ms; P < .01)

“These findings are in line with slower impulse formation and propagation among the retired athletes,” says Dermot Phelan, MD, PhD, Director of Cleveland Clinic’s Sports Cardiology Center and senior author of the study, which will be presented March 12 at the American College of Cardiology’s 67th Annual Scientific Session. “They add to a growing body of data on the long-term effects of strength sports on heart health and suggest there may be an upper limit of exercise beyond which maladaptive cardiac adaptations can occur.”

Latest in a series of heart studies in NFL alumni

This study is the second in a series of investigations on heart health in NFL retirees commissioned by the NFL Player Care Foundation. Data are being gathered through a program run by Dr. Phelan in 2014 that offered free cardiovascular screenings to former NFL players. The study is a collaborative effort involving Cleveland Clinic, the University of Texas Southwestern Medical Center and MedStar Sports Medicine Research Center.

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“Our goal is to define any unique cardiac problems these former athletes may have,” says Dr. Phelan.

The first study examined aorta size. Former NFL players were found to be twice as likely as matched general population counterparts to have an enlarged ascending aorta. Results were published last fall in Circulation: Cardiovascular Imaging and covered in a previous Consult QD post.

Findings brought surprises

“This second investigation targeted the heart’s electrical system,” Dr. Phelan explains, “because it has become increasingly clear that former elite athletes in endurance sports are at greater risk for arrhythmias and conduction issues. So we wondered if these problems were also present in athletes who participated in strength sports.”

Although athletes in training often have slower heart rates than their nonathlete peers, rates were thought to return to normal after training ceased. However, conduction tests during this study revealed that impulse formation and propagation were often delayed.

“Changes in the conduction system appeared to be more permanent than we expected,” Dr. Phelan notes.

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The researchers were also surprised that 61 percent of players diagnosed with AF were unaware they had it. “The very first athlete we screened was discovered to have atrial fibrillation that he was completely unaware of,” Dr. Phelan says. “He was asymptomatic.”

This finding should remind physicians who treat retired athletes to screen for AF and prescribe anticoagulants as appropriate. “Stroke risk may be low in some individuals, but most of the former players in this study needed medication to reduce the risk of stroke,” Dr. Phelan observes.

Next research steps

While these findings spotlight a potential hidden heart condition in aging football players, the study’s small size and self-selected cohort require replication in other studies before being taken as gospel. “If the data are robust and reproducible, we will need to pay attention,” Dr. Phelan says.

Ideally, he thinks NFL players should be followed yearly during and after their careers to define their risk of stroke, determine when they are at highest risk of developing AF and identify parameters for pinpointing players at highest risk.

Until this happens, he and his colleagues will keep mining the data they’ve gathered on the retired players. Their next paper will focus on the risk of coronary artery disease. “We hope to have it ready to present later this year,” he says.