BOSTON (AP) - Lew Carpenter never had any concussions - or at least none that his family knew about back in the 1950s and '60s, when he played for the Lions, Browns and Packers and there wasn't as much concern over them as there is now.
Still, when he began having trouble late in his life finding the right word, keeping things organized, remembering why he was going to the doctor or controlling his temper, relatives grew concerned.
After he died last year at the age of 78, they agreed to donate his brain to researchers studying a degenerative disease increasingly found in football players and other athletes who have absorbed repeated blows to the head. This week the results came in: Carpenter had an advanced form of Chronic Traumatic Encephelopathy.
"Concussions aren't necessary for CTE to exist," said Dr. Robert Cantu, a Boston University researcher working on the project in conjunction with the Veterans Administration Center for the Study of Traumatic Encephalopathy. "Even if he didn't have any concussions, the amount of subconcussive trauma that he had - he probably had between 1,000 and 1,500 subconcussive blows a year, just from practice and play in games."
Carpenter is the latest former athlete to be diagnosed with CTE, and the results are leading researchers down a new, perhaps more troubling, path: Damage may be caused as much or more by the low-level, or subconcussive, blows to the heads as by the big hits replayed on the highlight shows that leave a player wobbly.
"It's the total brain trauma. Tens of thousands of subconcussive blows all add up," Cantu told The Associated Press. "You can't draw a line between number of concussions and risk for CTE. You have to factor in the subconcussive trauma. It's equally - if not more - important."
Concussions are a growing concern among sports leagues, especially since the suicide of NFL defensive back Dave Duerson and the death of NHL enforcer Derek Boogaard; both were found to suffer from CTE, which can cause memory loss, disorientation, poor decision-making, and depression that can lead to drug use and even suicide.
The NFL and NHL have taken steps to crack down on the more violent head hits, and the pro football league has also cut back on full-contact practices that contribute to the wear and tear on all parts of the players' bodies. But the idea that brain damage could be caused by routine blocking at the line or a soccer player heading the ball cuts closer to the core of these sports' existence: Even if concussions could be eliminated, they would have to change even more drastically to eliminate this more mundane contact.
"We don't know for sure, but we expect that repetitive subconcussive blows play a tremendous role in the development of CTE," said Dr. Robert Stern, one of the researchers working on CTE at Boston University. "And if subconcussive blows do play a role in the development of this brain injury, then bigger changes have to occur."
Research on this hypothesis is only now beginning, Stern said. To make progress, scientists need data from a wider range of people so they can zero in on the causes of the disease.
"Brains that we really desperately need to study are the ones that we're not getting," Cantu said. "Those are the ones of people that have played in a collision sport ... and went on to live a normal life. In other words: were not symptomatic."
A star at Arkansas who was also offered a contract to play baseball for the St. Louis Cardinals, Carpenter signed instead with the Detroit Lions. He won his first NFL title as a rookie and led the team in rushing twice before he was drafted into the Army and served 18 months in Germany.
He returned to the NFL with the Cleveland Browns and played his last five years in Green Bay, winning two more NFL championships with the Packers.
After he was done playing, Carpenter embarked on an even longer coaching career, making stops in Minnesota, Atlanta, Washington, St. Louis, Houston, Green Bay, Detroit and Philadelphia in the NFL; at Southwest Texas State in college and the Frankfurt Galaxy of the World League of American Football.
Carpenter was never diagnosed with a concussion, to the best of his family's knowledge. He did not have evidence of Alzheimer's disease or any other neurodegenerative disease.
"Concussions are underreported even now, and were hardly ever discussed back in Carpenter's day," Stern said.
Said Cantu: "Over the course of his very long career, he undoubtedly took tens of thousands of subconcussive blows."
But his family began to notice signs of trouble. And the answers they were getting from his doctors didn't explain it.
"We didn't even know anything about CTE until my dad passed away," Carpenter's daughter, Lisa Prewitt, told the AP. "Knowing that he did have CTE, a lot of those things started to make sense."
Prewitt said her father would ask five times in the car to the doctor where they were going. "Then he arrived at the doctor's office and they started talking about football and he remembered every detail," she said.
"Looking back, if anybody along the line would have known that there was something so significant and he had it, there could have been a whole different approach to his care."
That's what researchers are hoping, too.
For now, CTE can only be diagnosed by a posthumous brain exam. Stern is hoping to develop a test that would identify the disease in living people, if not to treat it - there's no treatment yet - at least to tailor the person's care in a way that can keep them from disintegrating into depression and perhaps suicide.
"In order for us to really understand that, we need to be able to study people while they're alive," Stern said. "That, for me, is really the next step."