Strong safety David Bruton of the Denver Broncos is attended to by trainers after a play that would force him out of the game with a reported concussion during a game against the Oakland Raiders at Sports Authority Field at Mile High on Dec. 28, 2014, in Denver. (Doug Pensinger/Getty Images)

Out of 202 brains of deceased football players studied, CTE was diagnosed in 177 of them, a number that includes NFL, college and even high school athletes.

According to the Associated Press, “It’s the largest update on chronic traumatic encephalopathy, or CTE, a brain disease linked with repeated head blows.”

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While the nearly 90 percent of brains studied showed signs of CTE, the report doesn’t confirm that the condition is common in all football players, since the athletes whose brains were donated to a Boston brain bank had repeated concussions and showed troubling symptoms before death.

“There are many questions that remain unanswered,” lead author Dr. Ann McKee, a Boston University neuroscientist, told AP, including: How common is this in the general population and all football players? How many years of football is too many? What is the genetic risk? “Some players do not have evidence of this disease despite long playing years,” she noted.

The study also did not indicate whether a player’s lifestyle choices—such as alcohol consumption; drug use, including steroids; and diet—had any effect on the outcome.

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The test found CTE in “110 of 111 brains from former NFL players; 48 of 53 college players; nine of 14 semi-professional players, seven of eight Canadian Football League players and three of 14 high school players. The disease was not found in brains from two younger players,” AP reports.

The NFL, which has long denied the link between head trauma and brain disease, issued a statement to AP acknowledging the importance of the study and saying that it “will continue to work with a wide range of experts to improve the health of current and former NFL athletes.”

Recently the NFL reached a $1 billion settlement to compensate former players who claimed that the league hid the risks of long-term concussion studies.

“A lot of families are really tragically affected by it—not even mentioning what these men are going through and they’re really not sure what is happening to them,” Stacie Wainright—whose husband, former NFL tight end Frank Wainright, died in October at age 48 from a heart attack triggered by bleeding in the brain—told AP. “It’s like a storm that you can’t quite get out of.”

Read more at ESPN.