Dec. 22, 2011 -- It's not unusual for people to walk or talk in their sleep. But on Sunday morning, a New Jersey woman may have sleepwalked to her death.
The body of Charlene Ferrero, 55, was found Monday in Newton Lake near Oaklyn, N.J. Calls to the Oaklyn Police Department were not immediately returned, but WPVI in Philadelphia reports that police ruled her death an accidental drowning.
Ferrero's friends say when she walked to the lake a few blocks from her apartment sometime late Saturday or early Sunday, she may have been sleepwalking. Teresa Cerini, Ferrero's next door neighbor, told WPVI she had done it about a week and a half before her death.
"I heard a knock on the door, and I go, 'What are you doing up, honey?' And she goes, 'I'm so sorry. The people at Table 2 ordered the eggs,'" Cerini told WPVI.
Sleepwalking and other forms of parasomnia are not uncommon. According to the National Sleep Foundation, about 10 percent of Americans report some erratic nighttime behaviors like eating, walking, talking, having sex or even become violent while they are asleep.
But most sleepwalkers simply move from room to room in their homes. Only a few, like Ferrero, end up going farther.
"This case is extreme but not impossible," Dr. David Rapoport, director of the Sleep Medicine Program at New York University School of Medicine, told ABC News. "There are clearly cases of people doing complex things, and these can include driving or walking into dangerous situations."
WPVI reports that Ferrero was spotted driving her car on Saturday night. Cerini said she noticed the car parked awkwardly in front of Ferrero's apartment on the morning she went missing. She told WPVI that she thinks Ferrero may have sleepwalked and fell into the lake.
"Hitting the water and not being roused is unusual. We usually expect a person to wake up after that kind of stimulus," Dr. Helene Emsellem, director of the Center for Sleep and Wake Disorders in Chevy Chase, Md., told ABC News. "It's hard to know whether she was awakened by that impact or not."
Scientists know that sleepwalking is much more common in children, tends to run in families and can be aggravated by alcohol, stress, fatigue or insomnia. But exactly how the brain allows a person to perform complex tasks unconsciously is still a mystery.
"Different types of parasomnias may occur in different stages of sleep," Rapoport said. "It is not clear exactly what is happening, but the current thinking is that part of the brain is awake, while part remains asleep."
A few studies have linked certain medications to cases of sleepwalking and other parasomnias. In 2007, the U.S. Food and Drug Administration ordered Sanofi-Aventis to strengthen warnings on its sleep drug Ambien, after reports that the drug caused consumers to perform bizarre acts while asleep.
Emsellem said Ambien and other hypnotic drugs should be used under the guidance of a doctor and should never be combined with alcohol.
"These are do-not-pass-go drugs. You take them as you are getting in bed at your bedtime. Not at the time you wish you could go to sleep, but at your actual bedtime," Emsellem said. "We often see patients try to shift their sleep times with these drugs. Taking a medication at 9 p.m. for someone who usually goes to bed at 11 will actually probably not put you to sleep, but could increase the risk of these kinds of behaviors."
It is not clear whether Ferrero was taking any medications or had been using alcohol. The toxicology report will not be ready for a few weeks, WPVI reports.