Having sex while sleeping is more common than previously thought, according to research based on patients at a Toronto sleep laboratory.

One in 12 patients reported engaging in sexual activity while sleeping, says Sharon Chung, staff scientist at the Sleep Research Laboratory at the University Health Network’s Toronto Western Hospital.

The research will be presented today in San Antonio, Texas, at SLEEP 2010, an annual meeting of clinicians and scientists in the field of sleep medicine and sleep research. It includes the study and treatment of insomnia, narcolepsy, sleep apnea and parasomnia, which is unusual behaviour — including sexual behaviour — during sleep.

Parasomniacs may complain of not feeling rested, but do not know that they were walking, talking, or more rarely, eating or having sex while sleeping, unless someone else notices and tells them.

The review found it was more common in men than in women, about 11 per cent versus four per cent.

“We thought it was rare,” says Chung. “It’s a lot more common that we thought.”

The study was the brainchild of Dr. Colin Shapiro, head of Neuropsychiatry and the Sleep and Alertness Clinic at Toronto Western Hospital. He also runs the Youthdale Child and Adolescent Sleep Centre, which is not affiliated with the hospital.

Shapiro coined the term “sexomnia,” and has provided expert medical testimony about it at several criminal trials. His testimony helped acquit Jan Luedecke, a 37-year-old Toronto landscaper charged with sexual assault in 2003.

The verdict was controversial, and was opposed by women’s groups. On appeal, a verdict of not criminally responsible by reason of mental disorder was substituted and Luedecke was granted an absolute discharge.

In February, the Ontario Court of Justice refused to order Luedecke to register as a sex offender.

Shapiro said Luedecke had a history of engaging in sex with girlfriends while asleep. His mother and brother had histories of sleep-walking, indicating a genetic predisposition. Luedecke was drunk and had not slept for 20 hours when he fell asleep on a couch at a house party the night before the assault. Alcohol consumption can trigger parasomnia, and so can fatigue.

“In my mind it was a slam dunk. Not every case is a slam dunk, and the question for the court to decide is, is the evidence strong enough,” says Shapiro, who says he has testified at several trials.

One question Shapiro has often been asked, and could never answer, concerned the prevalence of what he calls “sexsomnia.” To find out, he added questions to the already lengthy questionnaire patients are required to fill out before undergoing overnight testing in the sleep lab, asking them if they had ever engaged in sexual activity while asleep.

Of 1,000 files reviewed, only 832 were tabulated, either because the questions relating to sexual activity had not been answered, or they had not been answered properly, according to Chung.

Patients were not contacted for verification.

James MacFarlane, director of education at the Medsleep network of clinics, and an assistant professor of pediatrics and psychiatry at the University of Toronto, vigorously disputes the use of the term “sexsomnia.”

“I think it’s a ridiculous and sensational word which has no scientific or medical merit,” says MacFarlane.

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“It’s not a real term. It adds to the drama of it all, but basically it comes under the heading of parasomnia.”

Sexsomnia does not appear in the current Diagnostic and Statistical Manual of Mental Disorders or the diagnostic manual for sleep disorders, MacFarlane points out.

“I think that’s the short answer.”

He also disputes the figures in the study. Having sex while sleeping is extremely rare, affecting a minority of people with parasomnia, which is also rare. He has seen about four cases in his career.

People who have parasomnia need to be protected from themselves and in some cases other people, says MacFarlane.

“They can walk over the edge of a ship. These people have to be made aware that they put themselves at risk in many ways, and potentially coming into contact inappropriately with other people in the night is one of those ways.”

Luedecke’s lawyer, Frank Addario, thinks it would be impossible for a person accused of sexual assault to fake parasomnia, because so much evidence is required to make the diagnosis. Luedecke and other members of his family underwent overnight sleep tests that found significant abnormalities in their sleep patterns.

He said Luedecke was traumatized by what happened and wants to put it behind him. Luedecke has no history of crime before or after the assault. He has taken significant steps towards ensuring it never happens again, including not falling asleep in “unsafe situations,” according to court documents.

“It’s a terrible thing to wake up and be told you did something you would never have done when you were conscious,” says Addario.

Joanna Birenbaum, legal director of the Women’s Legal Education and Action Fund, said there is concern for the potential for abuse of parasomnia or sleep disorders as a defence to sexual assault.

“The women’s movement has worked very hard to fight intoxication as a defence to sexual assault. In Luedecke the accused had consumed considerable alcohol before entering his state of parasomnia. We need to ensure that intoxication doesn’t suddenly re-enter the legal system as a defence in the name of parasomnia.”