It’s rare, but experts say it’s definitely possible to die while sleepwalking.

“Of course it’s dangerous,” said Dr. Colin Shapiro, a University of Toronto professor and director of the Youthdale Child & Adolescent Sleep Clinic.

“People can essentially do anything,” he said. “They can walk in their sleep, they can talk in their sleep, they can eat in their sleep, they can drive their car in their sleep and they can have sex in their sleep.”

And to fall and injure yourself, or die?

“It’s definitely possible,” Shapiro said.

The plausibility of such a demise has come up in the wake of Chris Hyndman’s death this week. The popular television personality was found dead in an alleyway next to the east end apartment where he lived with his on-screen partner and spouse, Steven Sabados. Hyndman’s mother told the Star she believes her son died in an “unfortunate accident” while sleepwalking.

Toronto Police repeated earlier statements on Thursday, with Const. Victor Kwong saying the investigation into Hyndman’s death is still open, but that no other information will be given because there is no suspicious or criminal element to the incident.

Though he’s never personally encountered a story of someone dying while sleepwalking, Sunnybrook Hospital sleep neurologist Brian Murray said such accidents have “undoubtedly occurred.” People have been known to fall from ledges or tumble down stairs, and there have been media reports from the U.S. and U.K. of sleepwalkers freezing to death after ambling outside in winter.

“We have lots of patients who have injured themselves and then come to us for treatment,” including people with spinal and head injuries, Murray said.

“For some people, it’s a real serious concern.”

Murray said it’s not clear exactly how many adults repeatedly sleepwalk, because many people live with the tendency but never report it. The best estimate, he said, is “a few per cent” of the adult population would have episodes of sleepwalking or somnambulation.

Two conditions are necessary for someone to sleepwalk, according to Shapiro and Murray. One must be in a deep sleep, and then quickly surface into a period of less profound slumber. This shift to a state between deep sleep and wakefulness is usually caused by what Murray calls an “arousal,” which could be a sudden noise, the jerking of a limb or a breathing irregularity.

“It’s that intersection between the two states where trouble occurs,” Murray said.

Sleepwalking is also precipitated by several factors that could push someone into a deeper-than-usual state of rest. Sleep deprivation and exhaustion from exercise can contribute, said Shapiro, as well as having a fever. The use of sleep medication or sleeping pills can also lead to sleepwalking.

“Anything that increases the depth of your sleep — so that could be sleep medication, that could be alcohol, that could be exercise, that could be staying awake too long,” Shapiro said.

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Sleepwalking has even entered the Canadian legal framework as a defence for homicide or sexual assault. In a case that was upheld by the Supreme Court of Canada in 1991, Kenneth Parks was acquitted of murder after testifying that he was sleeping when he drove to his wife’s parents’ home and stabbed his mother-in-law to death. More recently, Ontario’s top court ordered a retrial last month after a Brockville man appealed a sexual-assault conviction by arguing he committed the act in his sleep.

“It’s surprising the level of complexity that can occur,” said Murray. “Depending on the degree to which they tip into the spectrum (of sleepwalking), they could really do almost anything.”