SAN JOSE, Calif. — The retired soccer player Brandi Chastain remains best known for scoring the winning shootout goal in the 1999 World Cup final against China and for the jersey-shedding celebration that followed.

Now 47, a mother and a coach, Chastain hopes her latest move will do more for soccer than that. She has agreed to donate her brain to researchers at Boston University, pioneers in the study of concussions and chronic traumatic encephalopathy, a degenerative brain disease.

C.T.E., believed to be caused by subconcussive blows to the head, is a hot topic in sports like boxing and football. But C.T.E. has also been found in several male soccer players, and researchers believe that heading the ball is a primary culprit.

No female athletes have been found to have had C.T.E. — it has been found in the brains of women with histories of head trauma — but the sample size has been small. Researchers at Boston University have examined 307 brains, most of which belonged to athletes. Only seven of them were women’s.

But with soccer’s worldwide popularity and its growth among girls inspired by the likes of the United States’ women’s national soccer team, researchers are eager to learn more. For now, C.T.E. can be reliably diagnosed only with a brain examination after death.
Chastain is the second national team member to decide to donate her brain, after Cindy Parlow Cone. Both women, and several others from the 1999 team, have argued against heading in youth soccer. In November, U.S. Soccer announced stricter standards for players under 14, although Chastain and others believe that they did not go far enough.

Chastain spoke about her decision to donate her brain in San Jose, where she was born and raised. She also spends much of her time there coaching her 9-year-old son’s team; assisting on the varsity team at a Bellarmine, a private high school; and assisting her husband, Jerry Smith, the longtime head coach of the Santa Clara University women’s team. The following is an edited and condensed version of that conversation.

Q. Why donate your brain for study?

The N.F.L.’s Tragic C.T.E. Roll CallFEB. 3, 2016
A. If there’s any information to be gleaned off the study of someone like myself, who has played soccer for 40 years, it feels like my responsibility — but not in a burdensome way. People talk about what the ’99 group did for women’s soccer. They say, “Oh, you left a legacy for the next generation.” This would be a more substantial legacy — something that could protect and save some kids, and to enhance and lift up soccer in a way that it hasn’t before. That was the impetus for saying yes. If we can learn something, we should. And I won’t need it.

A. There are definitely days when I turn a corner and I’m like, “Why did I come into this room?” I have definitely, from time to time, thought, “Hmmm, I wonder if this is connected to the past 40 years of playing sports.” Soccer wasn’t the only thing I played. It’s crossed my mind. I do wonder about the ramifications over the next 20 years when I should be fully functioning and still doing things I like or want to do. I try not to get hung up on those things, because it doesn’t really matter at this point. You just don’t know.