Just days after a violent opening weekend to the 2015 season, results from an ongoing study show that 87 of 91 former NFL players autopsied by researchers had chronic traumatic encephalopathy, or CTE — a degenerative brain disease linked to repeat concussions — when they died, according to a Frontline report.

That means a whopping 96% of former players autopsied by the Department of Veteran Affairs and Boston University over the past decade had the disease. The autopsies are part of a joint study as information continues to emerge about the punishing effects a brutal sport has on the human brain.

Overall, researchers say 131 out of 165 of the football players’ brains they studied, which works out to 79%, showed signs of CTE. The study looked at brains from players at all levels of the sport, not just professional football.

Many doctors and researchers believe CTE is caused by repeated blows to the head, which football players subject themselves to regularly. The disease is believed to be linked to conditions such as depression, memory loss, aggression, lack of impulse control and more.

While the study results appear to be definitive and alarming, the Department of Veteran Affairs and Boston University researchers only autopsied brains of former players who agreed to donate their organs posthumously because, while alive, they or their families suspected they may have been suffering from CTE-related symptoms. The disease can only be definitively diagnosed after death.

That means researchers are working with a skewed sample. Thus, the new study has no predictive value regarding how many current football players will get CTE, nor is it representative of football players as a whole.

Nonetheless, it does represent another important step in what is still a relatively new field of medical research.

After Hall of Fame linebacker Junior Seau committed suicide in 2012, telltale signs of CTE were found in his brain. The 2013 book “League of Denial” details research into CTE and its effects, as well as efforts by the NFL to minimize and obfuscate medical findings, including by paying for its own research that came to opposite conclusions from the Boston University-led group.

That book is now the basis for “Concussion,” a forthcoming film starring Will Smith.

“People think that we’re blowing this out of proportion, that this is a very rare disease and that we’re sensationalizing it,” Dr. Ann McKee, who is running the collaborative CTE study, told Frontline.

“My response is that where I sit, this is a very real disease. We have had no problem identifying it in hundreds of players.”

Long-term brain damage due to football has become a much more prominent topic in the public eye since Seau’s suicide and the subsequent release of League of Denial. In March, star linebacker Chris Borland of the San Francisco 49ers retired after his rookie season because of concerns about his long-term health. Last September, two college quarterbacks retired from football due to similar worries.

At least one former NFL player took Friday’s news as an ominous sign:

What an exciting way to start my weekend. I probably have CTE. https://t.co/1Ct0MK9qCT

— Tom Crabtree (@itsCrab) September 18, 2015

That’s not necessarily true, given the new information’s skewed research sample. But it’s a good bet plenty of other former players are worrying about the same thing — and rightfully so.

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