WEDNESDAY, Sept. 5, 2012 (HealthDay News) -- Ex-National Football League players were more likely to die from neurological disorders than other men, according to a new study of more than 3,400 pros who played for at least five years from 1959 to 1988.
For players in "speed" positions -- such as quarterback, running back and linebacker -- death rates for Alzheimer's disease and amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease) combined were four times higher than for men in the general population.
While the study appears to support recent research showing an increase of diseases that damage brain cells among football players, it does not prove that playing pro ball is the cause. Other factors, including the football field surface and looser safety guidelines during the study period, may have played a role, experts say.
Also, chronic traumatic encephalopathy, a relatively new diagnosis associated with concussions and repeated blows to the head, might have been the actual or partial cause of death for some, the study suggests.
"Chronic traumatic encephalopathy has some commonalty among all the diseases -- ALS, Alzheimer's and Parkinson's," said study co-author Everett Lehman, an epidemiologist with the U.S. National Institute for Occupational Safety and Health. "There's overlap among the neurodegenerative diseases."
The study, published online Sept. 5 in Neurology, also looked at death rates for Parkinson's disease but found no difference from the general population.
For the three diseases combined, however, death rates were triple that of the general population.
The study looked at men with an average age of 57 and used diagnoses from death certificates for the 334 players (10 percent) who died through 2007. Of the players who died of neurological causes, 62 percent were speed players. For them, the risk of death from neurodegenerative diseases was tripled compared to offensive and defensive linemen, the researchers said.
While roughly 39 percent of players were black, they made up about 48 percent of the speed players, the study authors noted.
In recent years, responding to safety concerns, the NFL has made a series of rule changes to reduce head injury.
"They've moved the kickoffs up to the 35-yard line so there are fewer kick returns, and during kick returns there are a lot of high-speed collisions and I believe a lot of concussions resulted," Lehman said.
"They've tightened up the rules on hits and blocks to the head, and many more of those are penalized now than previously," he added.
"Spearing" players with helmets is also illegal, as is holding the quarterback and slamming him into the ground.
The NFL is also putting money towards a better understanding of the risks faced by players. On Wednesday, the league announced it was donating $30 million to the Foundation for the National Institutes of Health. The money will be earmarked for brain research designed to benefit athletes, members of the military and the general public, the Associated Press reported.
Kenneth Podell, a neuropsychologist and co-director of the Methodist Concussion Center in Houston, said the new study was "good" and "interesting." But he added that it "was done on relatively old data," not from current players.
"Back in the '60s and '70s, and even the '80s, the mantra was: 'You play.' And all those players went back and they would never sit out and they were never concerned about brain injury," said Podell, who is also team consultant with the Houston Texans.
Now, NFL players have to sit if they're diagnosed with a concussion, Podell pointed out. (College, high school and youth league football have instituted similar rules.)
"But the bottom line is, players are bigger now, they're stronger now, than they were 20 or 30 years ago," Podell said. And still, "there are a lot of defensive players out there that love to strike with their heads first," he noted.
"The 'speed' positions are more vulnerable to the incidence of concussions because they're more likely to be hit in the head, they're more likely to be hit on an angle," he explained.
Still, the study does not demonstrate cause and effect, "and the authors clearly make that distinction," he added. "They were unable to control for a lot of other factors that might be contributors."
For example, older players were more likely to play on grass than AstroTurf, and so had more exposure to fertilizer and pesticides, Podell said.
Lehman said turf might have been a factor, but only as it relates to concussion. "AstroTurf in the '70s and '80s was a much harder surface, and I think almost all the teams have gone away from that now," he said.
"What my study looked at were players in the past," Lehman said. "I think studies need to be done, and are being done, on current players: professional, college and high school players." He and his colleagues acknowledge that the study was limited by the small number of deaths.
While the findings concerning brain disorders were grim, another study result was not. The researchers found that pro football players had a lower overall death rate than others.
"I can't really extrapolate to the rest of football -- current players or any other sports -- but they had definitely a better mortality experience than we would see in the general population," Lehman said.
The U.S. Centers for Disease Control and Prevention has more on concussion in sports.