Former National Football League (NFL) players have a higher prevalence of atrial fibrillation (AF) and slowed cardiac conduction relative to age- and race-matched controls in the general population, concludes a large cross-sectional study published in the Journal of the American Heart Association. Moreover, 80% of the NFL retirees who had AF met indications for anticoagulation therapy to reduce stroke risk.
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“This is the first known study associating participation in strength-type sports with atrial fibrillation,” says the study’s senior and corresponding author, Dermot Phelan, MD, PhD, Director of Cleveland Clinic’s Sports Cardiology Center. “Its findings underscore a need for high levels of clinical suspicion for occult atrial fibrillation in former athletes in these sports.”
Second in a series of heart studies in NFL alumni
The investigation is the second in a series of Cleveland Clinic-led cross-sectional studies of heart health in NFL retirees commissioned by the NFL Players Care Foundation. Data were gathered via a program run by Dr. Phelan in 2014-2015 that offered free cardiovascular screenings to former NFL players.
“Our goal is to define any unique cardiac problems these former athletes may have,” says Dr. Phelan.
The first study, which examined aorta size, found that former NFL players were twice as likely as well-matched counterparts in the general population to have an enlarged ascending aorta.
The new study compared 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.
“This investigation targeted the heart’s electrical system,” Dr. Phelan explains, “because it is increasingly clear that former elite athletes in endurance sports are at greater risk for arrhythmias and conduction issues. So we wondered if these problems extend to athletes who participated in strength sports.”
The new investigation found AF to be present at a tenfold higher rate — 5.0% versus 0.5% — among the NFL retirees compared with the controls. Following multivariable regression analysis to adjust for other cardiovascular risk factors, the former NFL athletes still had an odds ratio for prevalent AF of 5.7 (95% CI, 2.1-15.9).
In addition, the former NFL athletes had…
- An eightfold higher prevalence of pacemaker implantation (2.0 %vs. 0.25%; P = 0.002)
- Lower resting heart rate (62 vs. 66 bpm; P < 0.001)
- Higher prevalence of first-degree atrioventricular block (18.0% vs. 9.0%; P < 0.001)
- A longer mean QRS interval (96 vs. 93 ms; P < 0.001)
These results, Dr. Phelan notes, are consistent with slower cardiac impulse formation and propagation among the retired athletes. “They add to mounting data on the long-term effects of strength sports on heart health,” he says, “and suggest there may be an upper limit of exercise beyond which maladaptive cardiac adaptations can occur.”
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.
A call for clinical vigilance — and more research
Most of the NFL retirees who were identified as having AF at screening were previously undiagnosed, rate-controlled and asymptomatic, but 80% of them met indications for oral anticoagulation therapy to prevent stroke.
This finding should prompt physicians who treat former strength-sport athletes to screen for AF and prescribe anticoagulants when appropriate. “There is a clear need to be vigilant for asymptomatic atrial fibrillation in this population,” Dr. Phelan observes.
At the same time, he and his co-authors point out that these findings need to be considered in the context of recent data showing that past participation in the NFL is associated with overall reductions in all-cause and cardiovascular mortality relative to the general population. “The effects of long-term participation in strength sports on cardiovascular health appear to be complex and nuanced,” Dr. Phelan concludes. “Much research work remains.”