(Reuters Health) - Nearly 20 percent of American adolescents, or one in five, has suffered a concussion, according to newly released statistics.

The odds were even higher for boys, with almost a quarter last year saying they had sustained a head injury and been diagnosed with a concussion.

Boys and girls who played contact sports were the most vulnerable. Nearly one in three teen competitors in contact sports reported having had a concussion.

The statistics, published in the Journal of the American Medical Association, represent the first count of adolescent concussions in the U.S.

The findings mirror those of a regional study of Canadian adolescents and came as no surprise to lead author Phil Veliz, a sociologist with the Institute for Research on Women and Gender at the University of Michigan, Ann Arbor.

“Sports participation is great,” he said in a phone interview. “It does have a downside, and that’s injury.”

Concussions symptoms include headache, dizziness, nausea and amnesia. Symptoms that should prompt an emergency room evaluation include confusion, difficulty waking or staying awake, vomiting and seizure.

Past studies have suggested that concussive impacts may contribute to changes in cognitive skills and physical brain changes in youth, high school and college-level players.

Veliz and his team analyzed responses to new questions about concussions in the annual national Monitoring the Future survey. For the first time, the questionnaire asked students in grades 8, 10 and 12 if they ever had a head injury that was diagnosed as a concussion.

An estimated 19.5 percent of more than 13,000 survey respondents said they had at least one diagnosed concussion.

Of students who played a contact sport in the prior year, 31.5 percent reported having had at least one diagnosed concussion, and more than 11 percent reported at least two.

Contact sports include football, lacrosse, ice hockey and wrestling, all competitions in which contact is officially sanctioned.

“Now we have a baseline number,” Veliz said. “Let’s hope people are putting interventions in place at the high school level. We want to see this rate going down.”

Dr. Matthew Eisenberg, an emergency physician at Boston Children’s Hospital who teaches pediatrics and emergency medicine at Harvard Medical School, told Reuters Health by email, “There’s so little we actually know about preventing concussions.”

Helmets can protect against brain swelling and bleeding but not concussions, he said, and neck strengthening and the use of proper tackling techniques can guard against concussions but are challenging to teach and implement.

“For now, we’re left with trying to monitor and identify concussions and get kids the care they need before they make things worse,” he said.

Eisenberg, who was not involved with the study, said he was struck by the differing incidence of concussion rates by race, with black and Hispanic teens reporting far fewer concussions than white teens.

Eisenberg said he suspects the lower number reflects teens of color being less likely to be diagnosed with concussion, not that they actually have fewer concussions. But the question requires further study, he said.

He also pointed to two limitations of the study. It relies on middle and high school students to report that they’ve been diagnosed with a concussion, and it cannot determine how many undiagnosed concussions students might have sustained.

“That’s a particularly big issue for teenage athletes who may not want to report concussion symptoms for fear of being held out of the game,” Eisenberg said.

Veliz would like to see a change in the culture of youth sports. He played football and wrestled during middle and high school and put his own body in jeopardy in response to the pressure he felt to win.

“We could be changing the rules of the game,” he said. “We could be changing the culture.”

“Maybe coaches shouldn’t push so much. Maybe athletes shouldn’t push themselves to a level where they’re going to actually cause serious damage to their body that’s going to have long-term effects,” he said.

Parents might urge their children to play sports with less contact and less likelihood for injury, he said.

When his 6-year-old son, who does martial arts, competes, Veliz said he tells him: “If you don’t feel comfortable doing something, just sit it out. You don’t have to prove yourself. You’re a kid. This isn’t your career. Just have fun.”

SOURCE: bit.ly/2wSOTm0 JAMA, online September 26, 2017.