As he suspected, a degenerative brain disease plagued former National Football League star Dave Duerson, who killed himself earlier this year, researchers announced today (May 2).

As he prepared to shoot himself in the chest Feb. 17, Duerson requested that his brain tissue be tested for chronic traumatic encephalopathy. Duerson was a four-time Pro Bowl safety who played in the Chicago Bears' and New York Giants' Super Bowl-winning seasons in 1985 and 1990, respectively.

Chronic traumatic encephalopathy is seen in people who suffer repeated blows to the head, including soldiers and athletes. CTE is characterized by the degeneration of brain tissue and the collection of tau protein in the brain. It is caused not only by concussions but by sub-concussive hits seemingly less-severe hits to the head that don't have immediate symptoms, said study researcher Robert Cantu, one of several co-directors of Boston University's Center for the Study of Traumatic Encephalopathy.

"The symptoms of CTE are in several different domains," Cantu said at a press conference. "There's an emotional element, with lack of impulse control being primary. Then, in the mood area, depression is frequently seen. And perhaps the hallmark finding: There are short-term memory failure and executive function difficulties, where multitasking and judgment is impaired."

The finding highlights the importance to monitor concussions experienced by both professional athletes and child athletes , researchers said. Coaches of contact saports should structure practices so that there is less heavy hitting and more training on other skills, said Chris Nowinski, another of the co-directors of the Boston University center.

Increasing signs

Duerson, who died at 50, had sustained at least 10 concussions during his 11-year NFL career, said co-director Dr. Robert Stern. The football player lost consciousness during several of those concussions but was never admitted to the hospital for any of them.

While a cause-and-effect relationship is hard to determine, Duerson did show some symptoms of CTE during and after his NFL career, Stern said.

"He had long-standing complaints of headaches over his NFL career and onward, and most importantly, over the five-year period or so prior to death, he had worsening short-term memory difficulties," Stern said.

In addition, during that time Duerson had a growing problem with impulse control, Stern said. He often had a short fuse and was hot-tempered.

"When it comes to suicide and CTE, it's possible in some individuals that a combination of CTE-related symptoms like poor impulse control, depression and cognitive impairment may lead to suicide," Stern said.

Looking at the brain

Duerson's brain showed evidence of CTE in the frontal lobe , temporal lobe, amygdala and hippocampus regions of the brain, said co-director Dr. Ann McKee.

"When you look at the brain, it's indisputable," McKee said at the press conference. "There was no evidence of Alzheimer's, no single beta amyloid- containing plaque. He has classic appearance of chronic traumatic encephalopathy."

The frontal and temporal cortexes and the amygdala likely affected his impulse-control abilities, and the changes in the hippocampus likely affected his memory, she said.

Researchers also noted that suicide is a common risk factor with CTE, McKee said.

Traumatic brain injury , including concussion, is associated with increased rate of suicide, and many of the brains donated to the Center for the Study of Traumatic Encephalopathy come from people who had committed suicide, McKee said.

"We've seen cases of moderately advanced CTE like Mr. Duerson had, where individuals committed suicide, and we've also seen suicide among young athletes that have recently experienced concussion," she said.

Currently there is no cure for CTE and a definitive diagnosis of the condition can be made only after death.

However, some diagnostic inroads have been made with preliminary tests using neuroimaging techniques. The goal of researchers is to find a way to diagnose CTE in life and to provide proper interventions for people with the disease, they said.

Pass it on: Dave Duerson, a former NFL star who died earlier this year, was plagued by a degenerative brain disorder called chronic traumatic encephalopathy.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @AmandaLChan.