As a longtime force in the players union, Duerson, 50, was keenly aware of chronic traumatic encephalopathy, the degenerative brain disease linked to depression, dementia and occasionally suicide among more than a dozen deceased players. He had expressed concern in recent months that he might have had the condition, said one person close to him who spoke on condition of anonymity.
The Duerson family got in touch with representatives of ’s , said Dr. Robert Stern, a co-director of the research group. Stern declined to comment further on Duerson’s specific case because of policies about confidentiality.
“This is a tragic event,” Stern said. “His wish will hopefully lead to additional scientific answers about this disease.”
Duerson’s request to have his brain examined for C.T.E., first reported by The Chicago Tribune, indicates how much acceptance of the disease has changed since it first made headlines in January 2007. That month, it was of the former player Andre Waters, who also had committed suicide.
Doctors, N.F.L. officials and even many players denied or discredited the links between football and such brain damage for months or even years. The roughly 20 cases of C.T.E. that have been identified by groups at Boston University and were almost always men who had died — most with significant emotional or cognitive problems — with no knowledge of the disease. Now, for the first time he knows of, Stern said, a former player has killed himself with the specific request that his brain be examined.
George Atallah, a union spokesman who knew Duerson well, said that active and retired players had become increasingly aware of, and occasionally quite concerned about, the prospect that they would develop C.T.E. or other issues regarding brain activity. He said some players had called the union’s office in Washington since Duerson’s death wanting to learn more about the condition.
“This thing has the whole union community pretty shaken up,” Atallah said in a telephone interview Saturday night. “The increased awareness around the long-term impact of head trauma on men that played football has been a constant subject of conversation among the players.”
It typically takes several months for the Boston University group to conclude an examination, which involves staining the tissue for abnormal protein deposits in various sections of the brain. The process cannot be conducted on a living person.
Duerson was a four-time Pro Bowl safety, primarily for the Bears. He helped the 1985 team win the as a member of its famed 46 defense, and was a member of the Giants team that won the Super Bowl five years later.
Duerson earned an economics degree from Notre Dame, and in 2001, he graduated from a Harvard Business School program. After many years in private business, he had spent the last several years as one of the union’s three representatives on the board that rules on retired players’ disability claims.
Often deadlocked 3-3 — evenly split among representatives of management and labor — that board has been criticized for denying the claims of players asserting cognitive decline caused by football. Specific votes are not made public.
Now, at Duerson’s request, his brain may contribute to knowledge of how — and how many — football players are at risk for C.T.E. Thirteen of the 14 deceased N.F.L. players who have been examined for the disease by the Boston University researchers have been found to have it, although that rate is skewed by the fact that many died in part through acts linked to the disease itself, like suicide, drug abuse or mental breakdown.
There also is a question as to whether the disease derives from a career in pro football or simply from many years of playing football at any level. Last year, C.T.E. was found in the brain of Owen Thomas, a who killed himself in April.