Atlanta, Georgia - At least 82 youths have died from the so-called "choking game," according to the first government count of fatalities from the tragic fad.

In the game, children use dog leashes or bungee cords wrapped around their necks or other means to temporarily cut blood flow to their head. The goal is a dreamlike, floating-in-space feeling when blood rushes back into the brain.

As many as 20 percent of teens and preteens play the game, sometimes in groups, according to estimates based on a few local studies. But nearly all the deaths were youths who played alone, according to the count compiled by the U.S. Centers for Disease Control and Prevention.

The CDC started the research after receiving a letter last year from a Tacoma, Wash., physician who said her 13-year-old son died from playing the game in 2005.

"At the time I had never heard of this," said Dr. Patricia Russell, whose son was found hanging in his closet, but later learned he had talked to a friend about it.

"One thing that really needs to happen - and is starting to happen now - is to get more information about how common this is," she said.

The CDC counted cases from news reports and advocacy organizations in the years 1995 through 2007, totaling 82 fatalities of children ages 6 to 19. They did not include deaths in which it was unclear if the death was from the choking game or if it was a suicide. They also did not include deaths that involved autoerotic asphyxiation, which is self-strangulation during masturbation and is said to be mainly done by teenage boys or men.

The 82 deaths were spread across 31 states. Nearly 90 percent were boys, at an average age of about 13, the CDC found.

Three or fewer deaths were reported from 1995 through 2004. They jumped to 22 in 2005, 35 in 2006 and at least nine in 2007. It's not clear what drove the increase in recent years, investigators said.

The report is being published this week in a CDC publication, Morbidity and Mortality Weekly Report.

CDC officials urged parents to be aware the fad exists, and to watch for possible warning signs like bloodshot eyes, marks on the neck, frequent and severe headaches, disorientation after spending time alone, and ropes, scarves or belts tied to bedroom furniture or doorknobs or found knotted on the floor.

The authors acknowledged that 82 is probably an undercount. They could not rely on death certificates, which do not differentiate choking-game deaths from other unintentional strangulation deaths. Instead, they relied mainly on a news database that is large but doesn't include all media outlets.

It's likely that there are about 100 U.S. choking game deaths each year, said Dr. Tom Andrew, New Hampshire's chief medical examiner, who has been studying the phenomenon for several years.

Andrew said many coroners and medical examiners likely label the deaths as suicides because they don't have the time or resources to interview a victim's friends and look for alternate explanations.

Many of the children who died from the choking game were described as bright, athletic students who apparently were intrigued by a method of getting high that doesn't involve drugs or alcohol, he said.

They watch it on YouTube, or hear about it in school or at summer camp, said Sharron Grant, a Canadian woman who was a founder of an advocacy group called Games Adolescents Shouldn't Play (GASP).

Choking game fatalities are not nearly as common as suicide deaths among youths who choose hanging or suffocation. About 5,100 such suicide deaths were reported from 1995 through 2007, and while it's possible some were unrecognized choking game deaths, most were believed to be actual suicides, said Robin Toblin, a CDC epidemiologist.

The game is also known by names that include "blackout," "space monkey" and "pass out," Toblin and others said.

Variations of the game have been around for decades, but the trend of doing it alone seems to be recent, Andrew said.