Brandi Chastain, whose shirtless celebration in the 1999 Women’s World Cup final is embedded in American sports lore, says she sometimes “can’t remember some details of a place we went . . . or somebody’s last name.” Michelle Akers, Chastain’s longtime teammate on the U.S. women’s national soccer team, has been fighting migraines for decades.

Speaking on “CBS This Morning” on Thursday, the two American soccer icons announced their participation in a Boston University study that will follow 20 former high-level female soccer players, all of them 40 or older, to determine the effect repeated headers have on cognitive ability later in life, specifically whether they cause chronic traumatic encephalopathy, or CTE.

“I am concerned that this game played by hundreds of millions across the globe might be played in a way right now that could lead to later life brain disease,” Boston University neurology professor Robert Stern said. “That’s pretty scary.”

Both players talked to CBS about the number of headers they took during their playing careers.

“I was the one, the target. So I won every punt by the goalkeepers,” said Akers, who at 5-foot-10 was usually among the U.S. national team’s tallest players. “As far as headers went … usually 50 a game.”

Said Chastain: “Oh, I did a lot of heading the ball. And very proudly so and very determined and very aggressive.”

But Chastain, 50, and Akers, 53, both have long wondered what effect the headers and other knocks to the head they took during games have had on their neurological health. In 2016, Chastain announced she would become one of the first female athletes to donate her brain to Boston University’s Concussion Legacy Foundation upon her death (CTE can only be formally diagnosed via autopsy), explaining that she suffered two concussions while playing in college at California and Santa Clara, staying in the game both times, and occasionally would “see stars” after using her head.

Akers, meanwhile, began to wonder about her condition after watching a 2017 documentary about former English soccer star Alan Shearer and his attempts to determine whether he was showing early signs of CTE.

“I was watching that and going, 'Oh my gosh, ' " Akers told CBS. “That could be me … and it stopped me in my tracks.”

But the possible connection between headers and neurological disorders goes back even further. In November 2002, a British coroner ruled that former England national team player Jeff Astle had died at 59 of what it described as an “industrial disease” — dementia brought on by repeated headers. Astle, a player known to use his head, helped England to the World Cup title in 1966, when soccer balls were much heavier. He often said it was like heading “a bag of bricks.”

Michael Alosco, assistant professor of neurology at Boston University, said the school’s study is looking for more female contributors and also is working with at-risk athletes who are still playing.

“We’re trying to do a similar thing with people who play contact sports, like soccer,” he said in an interview this month. “They’ll come in and complete a thorough neuropsychological battery of tests. They’ll get a brief neurological exam, and some of them will get an MRI. We’re trying to create a rich clinical picture of these people using standardized tests so we can understand what kind of impairments, if any, are present in females and can compare them to males, compare them to other types of contact sport athletes.”

The study involving Chastain, Akers and other former high-level female soccer players will include MRI exams of the brain and evaluation of cognitive function to establish baseline measurements, CBS reported.

Chastain now coaches youth soccer and told CBS that she has done a “180” in her thoughts about heading the ball.

“Heading five-story punted balls, no, not going to happen. We’re not doing that,” she said.

Akers told CBS she “would not be heading a million balls like that” had she been as knowledgeable about the issue during her playing days as she is now.

“There’s no way on earth I would do that again,” she added.

Cindy Boren contributed to this report.

Read more:

VAR is working at the Women’s World Cup, FIFA says. That’s not wrong, but it could work better.

Jerry Brewer: Megan Rapinoe isn’t here to make you comfortable

Trump invites USWNT to White House after Megan Rapinoe says she’s ‘not going’

She just missed the cut for the World Cup. Her two roommates are starring for the U.S.

USWNT gets its first taste of vulnerability ahead of its biggest World Cup test yet

Women’s World Cup bracket