In a 2009 survey of eighth graders in Oregon, one in 16 said they had participated in the "choking game," according to research published Monday.
The game -- a misnomer because of its risks, researchers say -- involves putting pressure on the neck with a towel or belt to cut off someone's oxygen supply, then releasing the pressure to give a "high" sensation.
The one-in-16 figure is in line with research from elsewhere in the United States and in other countries where youth are known to play the choking game, according to Dr. Thomas Andrew, New Hampshire's chief medical examiner.
"Of more concern in these studies that have been coming out over the last several years is that among that group... there's a smaller subset that seem to like the phenomenon enough to continue doing it on a regular basis," said Andrew, who has studied asphyxia games but wasn't involved in the new research.
Of Oregon kids who said they'd played the choking game, close to two-thirds reported having done so more than once, and more than a quarter had played at least five times.
"Some kids may experience it and say, 'This is the worst thing that's ever happened to me. I'm never going to do it again,'" Andrew told Reuters Health.
"The kids that go on to repeat it, it may not be in groups anymore. It could escalate into doing it by yourself with a ligature, and of course that's the highest risk of all."
Along with the risk of asphyxiation, the choking game comes with a chance of seizures that can cause brain damage, Andrew said. He's also seen cases of kids with fatal head injuries from when they hit the ground after their air supply was cut off.
"The more times you repeat something like this, the better the chance of a bad outcome," said Robert Nystrom, from the Oregon Public Health Division in Portland, who worked on the study.
His team's findings are based on a 2009 survey given to more than 5,000 Oregon eighth graders. The researchers found that kids who were sexually active and those who used drugs or alcohol were more likely to have played the choking game -- also known as Knock Out, Space Monkey or Flatlining -- than abstainers.
Boys and girls were equally likely to have participated.
The U.S. Centers for Disease Control and Prevention found 82 media reports of kids dying from playing the choking game from 1995 through 2007 -- but that the figure is likely an underestimate, Nystrom and his colleagues write in Pediatrics.
If a kid asphyxiates trying to get high alone, the death could look like a suicide, for example.
While groups of youth have been playing asphyxiation games for generations, researchers said they may be more dangerous and contagious now than they used to be.
"The activity itself is not new, but I think the ability to spread the word about it via the internet is adding some fuel to the fire," said W. Hobart Davies, a psychologist from the University of Wisconsin-Milwaukee who has studied the choking game but didn't participate in the new research.
"If you watched the kids doing it on YouTube, you'd think it was the most fun thing people have ever done," he told Reuters Health.
That's why the most important message is for parents and other adults who work with kids not to be afraid to bring up the choking game and its risks, researchers agreed.
"By eighth grade, kids already know. They're talking about this," Nystrom told Reuters Health.
Teaching kids and teens about the dangers of the game should be part of programs that also address drugs, alcohol and risky sexual behavior, Andrew said.
He pointed to one study that showed 40 percent of kids surveyed in Texas and Canada didn't see any danger in playing the choking game, whether or not they had ever participated themselves.
"I hope that it just becomes a part of the conversation," Andrew said.
"It's not perfectly safe, and that's the message that we need to get across."