Auto-Erotic Asphyxia's Deadly Thrill

June 5, 2009— -- The mysterious death of actor David Carradine -- perhaps by auto-erotic asphyxia -- focused renewed attention on a practice that is one of the greatest and most dangerous sexual taboos.

The 72-year-old actor was found dead in a Thai hotel room closet in an intricate web of ropes -- one around his neck, another around his genitals and the two tied together, according to Thai authorities.

Sex experts say that Carradine's advanced age suggests that he may have been a lifelong practitioner of the secretive and dangerous practice, one that can go fatally awry.

Los Angeles Superior Court documents of Carradine's divorce put online by The Smoking Gun show that his most recent ex-wife, Marina Anderson, accused the actor of "deviant sexual behavior which was potentially deadly." The alleged behavior wasn't described in the court documents.

Also known as hypoxyphilia, the practice is a sub-category of sexual masochism that involves reducing the oxygen supply to the brain while masturbating to achieve a heightened orgasm.

"There's a fine line between the state of hypoxia [lack of oxygen in the brain] and death, and it's in that state that a person becomes highly aroused and it's what allows them to orgasm," said Eli Coleman, chair of the sexual health department at the University of Minnesota.

"People usually have safety nets and no intention to die, but something often goes wrong in their calculation," he told ABCNews.com. "Maybe a stool or something they are standing on somehow slips away."

The Federal Bureau of Investigation estimates there are between 500 and 1,000 such deaths in the United States annually, mostly among young men. Many more may be falsely ruled as homicides or suicides.

Auto-erotic asphyxia often starts in adolescence, which is why many of the deaths associated with the practice are among young adults. But, the practice is not unknown among girls, according to Coleman.

Because it is practiced alone, AEA is particularly dangerous. It is a compulsive activity that can also escalate, as may have been the case with Carradine, said Coleman.

"We know very little about the people who practice this," he said. "Most of what we know is from those have accidentally died."