MONDAY, April 16 (HealthDay News) -- In a new study, about 6 percent of eighth graders admitted they had participated in the "choking game," in which blood and oxygen to the brain are cut off with a rope or belt to produce a euphoric "high."

What's more, the researchers found that two-thirds of those kids had played the dangerous game multiple times and many practiced other risky behaviors.

"If kids do participate, they are likely to do it more than once," said lead researcher Robert Nystrom, adolescent health manager at the Oregon Public Health Division in Portland. Of the 6.1 percent who admitted to trying the game, about two-thirds had done so more than once and nearly 27 percent had done it more than five times.

The study is published online April 16 in the journal Pediatrics.

Nystrom's team did not gather data on deaths, but the U.S. Centers for Disease Control and Prevention has reported that 82 children died from the activity in the years 1995 through 2007.

Those who play the game, also called Knock Out, Space Monkey, Flatlining or the Fainting Game, can lose consciousness within seconds, according to the CDC. Within three minutes of continued strangulation, such as hanging, basic body functions such as memory, balance and the central nervous system can fail. Death can occur shortly after, according to the CDC.

For the new survey, Nystrom and his colleagues obtained data from the 2009 Oregon Healthy Teens survey. It included nearly 5,400 eighth graders -- ages 12 to 15 -- who answered questions about the choking game as well as questions about their physical health, sexual activity, exercise, nutrition, body image, substance abuse and exposure to violence.

"Males and females seem to participate equally [in the game]," Nystrom said.

Those who did participate tended to engage in other risky behaviors, Nystrom's team found. They were more likely to be sexually active and to be substance abusers.

Girls who engaged in the game were more likely to gamble and have poor nutrition; boys were more likely to be exposed to violence.

Black boys were more likely to have played the game than white boys, and Pacific Islanders of both genders were more likely than whites to have tried playing, the researchers found.

However, Nystrom cautioned, there may not have been enough ethnic diversity in the sample to be sure that those findings would hold up.

Dr. Dennis Woo, a staff pediatrician at the UCLA Medical Center in Santa Monica, said he was surprised that the number of kids participating was that high. "Six percent is quite a few kids," he noted.

Parents can help their children avoid problems, he said, by being aware that age 13 is a time when youth are transitioning to adulthood, and trying to find themselves.

Be aware, Woo said, of your children's friends and their activities. Be alert to behavior changes, such as suddenly not doing well in school, because that might indicate they are getting involved in risky behaviors.

"I think it's still OK to have an open door policy," he said, striking a balance between giving them "alone time" in their room but also having access. "Remind them they are still subject to random searches."

Some parents are casual about risk-taking behavior in their pre-teens and teens, he said, reasoning that "kids will be kids." But he would tell those parents that "you really do want to be vigilant because some of the behaviors can have tragic consequences."

Nystrom agreed that parents need to talk to their children and stay aware of any warning signs of the game activity. That could include marks on the neck, red dots around the eyelid (reflecting hemorrhage) and unexplained headaches, he said.

Contact the child's health care provider right away if you suspect something, he said. At the child's annual wellness visit, the pediatrician should do a comprehensive physical and include a risk assessment, he added.

More information

To learn more about the choking game, visit the U.S. Centers for Disease Control and Prevention.