Diagnosed with ALS in May 2025, former NFL running back Chris Johnson says he wonders whether football played a role. Doctors have not identified a cause in his case, and a study found higher ALS rates among NFL players but did not establish football as the cause.
A JAMA Network Open study examined 19,423 players who appeared in at least one NFL game after debuting from 1960 to 2019; researchers identified 38 ALS diagnoses. Adjusted for age and race, ALS incidence was about 3.6 times higher and mortality about 3.9 times higher than expected among U.S. men. The researchers could not determine which exposures accounted for the difference and lacked direct data on players’ head impacts, injuries and other potential risk factors.
Johnson first noticed weakness in his right hand in early 2025. A September Sports Illustrated profile described him as unable to speak or walk without significant assistance; PEOPLE reported that he uses an electric wheelchair and relies on his wife, Brittany, for daily care. Their 14-year-old twin sons play competitive football, and Johnson says he supports them continuing while thinking more carefully about the risks.
