NFL wide receiver who mysteriously died days before his 34th birthday had CTE, tests show

• Boston University's CTE Center diagnosed Demaryius Thomas Tuesday with stage 2 CTE.
• Thomas was a retired NFL wide receiver when he died at 33.

On Tuesday, former NFL wide receiver Demaryius Thomas was diagnosed posthumously with CTE, a brain disease linked to repeated head trauma.

When he died in December, the Super Bowl champion was 33, and a recent retiree from the Denver Broncos. Dr. Ann McKee, the neuropathologist who studied his brain, said he had two conditions: CTE and seizures stemming from a 2019 car crash, The New York Times reported.

While his cause of death has not been determined, doctors believe Thomas died of suffocation after a seizure, according to The Times.

Seizures are not primarily associated with CTE, McKee said.

Friends and family said Thomas experienced many symptoms of CTE in his final year of life, including memory loss, increased erratic behavior, and paranoia.

A week before Thomas' diagnosis, Scott Vermillion became the first Major League Soccer player to be diagnosed with CTE. Vermillion died in December 2020 from an accidental drug overdose and displayed similar erratic behavior and isolation in the years leading up to his death.

McKee told Insider there hadn't been enough action taken by major-league sports teams to protect players.

"There have been changes. The changes have not been enough," she said.

McKee said she believed rule changes, neuropsychological exams, MRIs, and blood biomarkers of players pre- and postseason could help prevent cases like Thomas' and Vermillion's. McKee said research was about five years out from identifying the disease in living people, which she hopes will bring more public awareness.

"Once we get people to actually listen long enough so that they understand who this is damaging, then we're going to see a change in the public demanding that the sports leagues do something about this disease," she said.