Update (Nov. 6, 2012):This story was updated to reflect the availability of an abstract of the scientific paper (online and print) on which the story is based, as well as information about an upcoming webinar on this subject.
New data shows that — while overall risk of death among National Football League (NFL) players is less than that of men in the general U.S. population — the risk of death related to amyotrophic lateral sclerosis (ALS) is four times higher.
The increased risk was observed only in men who played in "speed" positions — a classification which designates players who have a higher risk of concussion due to factors such as high acceleration and multiple impacts experienced during games. (A concussion is a trauma-induced brain injury that can occur with or without a loss of consciousness, and that may affect mental functioning.) Risk of death related to ALS was not increased in men who played in "nonspeed" positions, which typically involve more — but less forceful — impacts.
Study researchers noted that more studies are needed to definitively pinpoint the cause of the increased risk of ALS in NFL football players, but high-impact head injuries are a plausible candidate.
It has been suggested in previous studies that football players who have experienced head injuries, including concussions, may be at higher-than-average risk for developing a motor neuron disease. However, other studies have found a lack of association between head trauma and ALS.
Findings from the study, conducted by the National Institute for Occupational Safety and Health (NIOSH) under the auspices of the U.S. Centers for Disease Control and Prevention (CDC), were published online Sept. 5, 2012, in Neurology.
Study investigators identified 3,439 NFL players who played for at least five seasons between 1959 and 1988. Of these, they found that 10 percent (334) were deceased. They then matched deceased players with the causes of death listed on their death certificates, obtained from the National Death Index (a database that provides data on the causes of nearly all deaths in the United States since 1979).
The researchers looked at death in 119 categories, including three related to degeneration of brain tissue (neurodegeneration): Alzheimer's disease (AD), Parkinson's disease (PD) and ALS.
Twenty-seven NFL player deaths were associated with neurodegenerative conditions: 13 from ALS, nine from AD and five from PD.
The players were divided into two categories:
The researchers found that, regardless of the position they played, the NFL players’ risk of death from all causes was half that of the general population of U.S. men. But their risk of death associated with neurodegenerative causes (ALS, AD and PD combined) was three times higher than in the general male population.
More specifically, an NFL player’s risk of dying from either ALS or AD was four times higher than in the general male population.
Researchers found that among “speed” players, the risk of death due to neurodegenerative causes was three times higher than in “nonspeed” players.
The results, the researchers wrote, “provide additional support for the finding that professional football players are at an increased risk of death from neurodegenerative causes."
The researchers were unable to look at deaths due to chronic traumatic encephalopathy (CTE), a disease associated with head and brain trauma that causes symptoms similar to those found in people with AD, PD and ALS.
CTE recently has been defined as a neurodegenerative condition caused by progressive loss of motor neuron function that occurs after exposure to multiple concussions. People with CTE experience altered mental status, and impaired balance and movement.
CTE could not be included as a cause of death in the study because the parameters of the disease only recently have been determined and refined. In addition, the disorder is not listed as an official cause of death in the International Classification of Diseases (ICD).
In order to account for CTE — which may have been the actual cause of some deaths attributed to AD, PD and ALS — total deaths from all three neurodegenerative causes (AD, ALS and PD) were combined for some comparisons.
If some of the deaths attributed to AD, PD and ALS in this study were in fact due to CTE, the actual risk of NFL player death from these specific diseases is somewhat less certain — although there seems to be a clear link to neurodegenerative diseases as a whole.
Other study limitations
The small number of deaths related to neurodegenerative causes made the study results "highly imprecise," the researchers noted.
Small numbers limited the investigators' ability to classify players into more than two categories (speed and nonspeed). More categories would have made possible the identification of any differences in risk for each position within the speed group, and it's unknown whether the findings apply to football players who play short-term or in non-professional leagues.
Additionally, the investigators did not take into account data on specific injuries and concussions for each player. They noted that if "chronic mild to moderate concussion" does raise the risk of death related to a neurodegenerative disease, "the magnitude of risk may depend on the intensity and frequency of brain injuries incurred over a number of years."
And finally, no other environmental, genetic or other risk factors for neurodegenerative disorders were considered.
“CTE is an ALS-like condition that could have artificially contributed to the apparent increase in death associated with ALS,” said Sanjay Bidichandani, MDA vice president of research. “Also, the study looked at players who were active from 1959 through 1988. It’s unclear whether the same increased association with neurodegenerative diseases would be seen now, with the use of modern protective gear and other changes in the game in recent decades.”
To learn more about ALS and CTE, read: