Chris Henry, the Cincinnati Bengals receiver who died during a domestic dispute last December, has been identified by experts as the first player to have died with trauma-induced brain damage while still active in the N.F.L.

Dr. Julian Bailes and Dr. Bennet Omalu of the Brain Injury Research Institute at West Virginia University announced on Monday that Henry, 26, had developed chronic traumatic encephalopathy, the progressive brain disease whose recent discovery in some retired N.F.L. players has raised questions of football’s long-term safety risks.

The 22nd professional football player to be given a diagnosis of C.T.E., Henry is the first to have died with the disease while active after 2007, when prior C.T.E. findings prompted the N.F.L. to begin strengthening rules regarding concussion management. The fact that he developed the condition by his mid-20s  the youngest previous C.T.E. case was the lineman Justin Strzelczyk, 36, who had been retired from the Pittsburgh Steelers for five years before his death in 2004  raises questions of how many current N.F.L. players might have the condition without knowing it.

“As we got the results, my emotion was sad  it’s so profound,” said Bailes, the chairman of the department of neurosurgery at West Virginia and a former team physician for the Steelers. “I was surprised in a way because of his age and because he was not known as a concussion sufferer or a big hitter. Is there some lower threshold when you become at risk for this disease? I’m struggling to see if something can come out positive out of this.”