A new study of more than 6,000 former professional athletes found that National Football League players died at a rate that was almost 1.3 times higher than Major League Baseball players. It’s the first to compare mortality rates between two groups of professional athletes; previous studies that compared professional athletes to the general population showed a lower risk of death for football players.

The findings, published Friday in JAMA Network Open, come amid growing concern about head trauma among current and former NFL players and their risk of developing the neurodegenerative disease CTE, or chronic traumatic encephalopathy. The NFL players died of neurodegenerative diseases at a higher rate than MLB players, though both groups of athletes were more likely to die of cardiovascular disease than brain diseases.

“There is so much press and buzz around the neurocognitive stuff, and that was one of the important things to come out of this,” said Marc Weisskopf, an environmental epidemiologist at the Harvard T.H. Chan School of Public Health and a study co-author. “But for cardiovascular disease, the number was higher, and since it’s more common, let’s not lose sight of the fact that it’s a very important issue.”  

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Previous studies looking at mortality rates among NFL players compared them to the general population and found that NFL players tended to fare better. One study from 2012 found that NFL players had overall decreased mortality as well as lower cardiovascular mortality than the general population. Another paper that year also found that overall mortality in NFL players was reduced, but did find that they had rates of neurodegenerative mortality that were three times higher than the general population.

But the limitation with these and other previous studies that compared professional athletes to the general population, experts say, is that they contained a “healthy worker bias.” Employed people already tend to be healthier than the unemployed, but as professional athletes, this effect is likely to be enhanced when it comes to NFL players versus the general population, explained Kathleen Bachynski, a public health and sports safety researcher at NYU Langone Medical Center.

“That can muddy things up,” she said.

With the new study, there’s a more apples-to-apples comparison — two kinds of elite athletes — helping to eliminate such a bias.

“I think that’s kind of the crux of why they chose to go with another comparable, elite, athlete group,” Bachynski said.

Researchers looked at data from the NFL cohort, which was a database constructed by the National Institute for Occupational Safety and Health in the ’90s and contains information on former players who participated in at least five seasons between 1959 and 1988. Weisskopf and colleagues then generated a comparable dataset for former MLB players. By then matching the 3,419 NFL players and the 2,708 MLB players to the National Death Index — which contains records and causes of deaths of U.S. citizens — the researchers compared mortality rates between the two groups.

The new work found that NFL players were about 2.5 times more likely to die from cardiovascular disease and almost three times more likely than MLB players to die from neurodegenerative disease.

“That ‘three times more likely’ sounds dramatic, but we have to think in terms of absolutes,” Weisskopf said.

And to get at the absolutes — or what that rate translates to in actual numbers — Weisskopf and others calculated what the number of deaths from each disease type would have been had they followed 1,000 players from either sport until the age of 75. In that case, 77 more football players would have died from cardiovascular disease, while 11 more would have died from neurodegenerative conditions, and 21 more would have died overall.

“Obviously we want to eliminate any difference, but it’s important to keep in mind that that is a small number,” Weisskopf said of the deaths from neurodegenerative disease.

Among the NFL players in the study, far more died of cardiovascular disease than neurodegenerative disease: nearly 500 versus 39, respectively.

“Cardiovascular issues are things we know we can do something about,” Weisskopf said. “If that message isn’t getting out there, we want to make sure people can get that.”

In a statement, an NFL spokesperson said: “The NFL and NFL [Players Association] have a long-standing and on-going commitment to provide current and former NFL players resources for their health and well-being on and off-the-field to achieve physical and emotional wellness.”

Neither organization funded this study, although many of the authors have received funding from the groups for other work.

“It is a sobering message,” said Dr. Dermot Phelan, a sports cardiologist at the Cleveland Clinic who consults with the NFLPA and helps with its events that screen prospective NFL players. “It does highlight the fact that we need to be extra vigilant and players need to participate in more of these [screening] facilities.”

But what may be driving these disparities is still a mystery and more research is needed to tease out the reasons. Fundamental differences between the two sports may only partially explain some of the findings.

NFL players often weigh more than MLB players, for instance, and are even incentivized to bulk up to handle the high levels of contact. But excess weight is also associated with a heightened risk of cardiovascular disease.

Even if differences in the games could explain the findings, it’s unclear whether they are relevant to today’s players.

“The cohort is from an older generation and all of these changes may have nothing to do with playing in the NFL or playing in the MLB,” Phelan said.

NFL rules have also changed in recent years to promote safety: Certain types of blocks and tackles are not allowed, for instance, and there are now penalties for head-to-head contact on the field.

“‘Monday Night Football’ in the ’90s used to show ads that showed two helmets crashing together,” Bachynski said. “It’s really only recently we’re saying, ‘Maybe we shouldn’t celebrate that.’”

Still, “it’s all part of a life in football,” said Dr. Ross Zafonte, a physical medicine and rehabilitation specialist at Spaulding Rehabilitation Hospital in Boston and a co-author of the new study. “It’s a life in this sport and perhaps we can do something by changing how people exit [the sport].” If you no longer actively play, for instance, but continue to train aerobically and eat right, he said, “it is possible that we could affect that [risk] and affect it pretty significantly.”

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