Research conducted on 202 former football players found evidence of brain disease in nearly all of them.
A new study published Tuesday in the Journal of the American Medical Association, looked at the brains of 202 deceased American football players who donated their brains for research. Chronic traumatic encephalopathy (CTE), which is a brain disease linked to repeated head blows, was found in 99 percent of former NFL players' brains.
Many of the donors or their families contributed because of the players' repeated concussions and troubling symptoms before death. Because most brains studied were donated by concerned family members, researchers acknowledged that there's a lack of a comparison group that is "representative of all individuals exposed to American football at the college or professional level."
"There are many questions that remain unanswered," said lead author Dr. Ann McKee, a Boston University neuroscientist.
McKee added that it's unclear whether some players' lifestyle habits like alcohol, drugs, steroids and diet could have contributed in some way.
Still, McKee said in the future research from the Boston brain bank may help doctors understand how to detect the disease when players are still alive. Currently, there is no known treatment for CTE.
The Associated Press contributed to this report.