Professional football players in the NFL are four times more likely to develop and die from ALS than the adult male population, according to new research.
Scientists at Boston University's CTE Center, who conducted the study released Wednesday, said they couldn't determine exactly why the rate was higher for those athletes but suggested that repetitive head impacts and traumatic brain injuries may play a role.
Amyotrophic lateral sclerosis, also known as Lou Gehrig's disease, is a fatal neurodegenerative disease with no known cure. ALS has been linked to chronic traumatic encephalopathy, or CTE, another degenerative brain disease found in many former football players.
Researchers examined all 19,423 NFL players who took the field for at least one game from 1960 to 2019 in what the scientists said was the largest study of ALS risk in professional football players. Previous, smaller studies have also found links between league play and the disease.
The latest study found that 38 players had received an ALS diagnosis during the study period and 28 had died, a four-fold increase over the rates for the overall U.S. male population adjusted for age and race.
NFL players who developed ALS had significantly longer careers than those who didn't get the disease, but researchers said other factors like a player's position, body mass index and race didn't show any differences.
Other factors such as smoking, strenuous physical exertion and exposure to environmental toxins such as pesticides may also increase the risk of ALS for NFL players, the study said.
The NFL did not immediately respond to NPR's request for comment.
A version of this story originally appeared in the Morning Edition live blog.
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