Former Tennessee Titans running back Chris Johnson visits the field during the second half of an NFL football game against the New York Jets, Sept. 15, 2024, in Nashville, Tenn. (AP Photo/George Walker IV, File)

New York Jets running back Chris Johnson (21) carries the ball against the Tennessee Titans in the second half of an NFL football game, Dec. 14, 2014, in Nashville, Tenn. (AP Photo/James Kenney, File)

NASHVILLE, Tenn. (AP) — Chris Johnson has been to every major ALS clinic in the country and seen neurologists respond once they learn he played football. The sixth man to run for 2,000 yards in an NFL season read the study that found former NFL players were nearly four times as likely to develop and die from ALS than other men.

“Obviously, I can’t help but wonder if there’s any connection between my career and where I am now,” Johnson wrote in a letter to his four children published Thursday by The Players Tribune.

Still, Johnson wrote he remains glad for his chance to play in the NFL even as he went from noticing weakness in his right hand last year to needing a computerized speech-generating device to speak this year.