Hockey player Derek Boogaard, who died in May, was in the early stages of a degenerative brain disease, researchers said today.

Boogaard's brain showed signs of chronic traumatic encephalopathy (CTE), a condition seen in football players, boxers and other athletes, in which the brain slowly degenerates over time because of repeated blows to the head.

Boogaard died May 13 at the age of 28 of an accidental overdose of alcohol and the painkiller oxycodone, according to ESPN. His brain showed evidence of early CTE in his cerebral cortex, according to the findings of Dr. Ann McKee, co-director of the Boston University Center for the Study of Traumatic Encephalopathy.

The severity of Boogaard's brain changes were more advanced than most other athletes of similar age with CTE, McKee's findings showed. CTE can only be diagnosed by examining brain tissue postmortem.

Boogaard dealt with drug addiction and exhibited abnormal behaviors, including emotional instability and problems with impulse control, along with short-term-memory problems and disorientation, for two years prior to his death, according to a statement from the center.

He had not played professional hockey since Dec. 9, 2010, because of injuries he sustained in a fight, including a reported concussion. Boogaard had been diagnosed with post-concussion syndrome twice, and his family said he spoke of having at least 20 mild concussions, although he reported few of them to his team or medical staff.

Boogaard reportedly participated in 174 career fights in professional hockey, according to the center.

“Very few hockey players engage in as many fights as Boogaard,” said Chris Nowinski, co-director of the center, so the finding does not contribute to researchers' knowledge of the risks of normal hockey playing. “Athletes and parents should know that anyone who experiences repetitive brain trauma may be at risk to develop CTE, but we are hopeful that risk is small in hockey.”

Nowinski added that two other young non-NHL professional hockey players studied did not show signs of CTE at postmortem examination.

“It is important not to over-interpret the finding of early CTE in Derek Boogaard,” said researcher Dr. Robert Cantu. “However, based on the small sample of enforcers we have studied, it is possible that frequently engaging in fistfights as a hockey player may put one at increased risk for this degenerative brain disease.”

Still, the link between the structural changes seen in Boogaard’s brain and the behavioral changes and memory problems  he experienced is unclear, the researchers said. His behavioral changes occurred during the same time period he was exhibiting narcotic abuse.

Just days before Boogaard died, the same researchers had announced that football player Dave Duerson suffered from CTE, according to their examination of his brain. Duerson committed suicide in February, and had sustained at least 10 concussions during his 11-year NFL career.

McKee also found mild stages of CTE in former NHL players Rick Martin and Bob Probert, and advanced CTE in Reggie Fleming. For 30 years, Fleming showed worsening behavioral and cognitive difficulties, and died in 2009 at the age of 73 with dementia.

McKee has analyzed the brains of over 70 former athletes and more than 50 have shown evidence of CTE, according to the center.

Boogaard played left wing for the Minnesota Wild from 2005-2010 before playing for the New York Rangers during the 2010-2011 season.

Pass it on: Fights In professional hockey games might have contributed to hockey player Derek Boogaard's development of a degenerative brain disease.

Follow MyHealthNewsDaily on Twitter @MyHealth_MHND. Find us on Facebook.