A new study from Montreal researchers adds support to the growing belief that behaviours like sleepwalking and sleep terrors run in families. The findings were published Monday in the journal JAMA Pediatrics.
The offspring of parents who are or were sleepwalkers are between three and seven times more likely to sleepwalk than other children, report the researchers, from the Centre for Advanced Research in Sleep Medicine at Sacre Coeur Hospital, a teaching hospital of the University of Montreal.
The likelihood rises if both parents have a history of sleepwalking. Researchers found that in families with two parents who are or were sleepwalkers, nearly two-thirds of the children experienced sleepwalking incidences.
Among the children studied, about 47 per cent of the sleepwalkers had one parent with a history of sleepwalking. Nearly 23 per cent of the children who were sleepwalkers had parents with no history of somnambulism.
"Not all sleepwalking is problematic," noted first author Dominique Petit, a research assistant at the centre.
"Very often you don't need to do anything with sleepwalking. (But) in some rare cases there's potential for injury."
Sleepwalkers can navigate around their households with relative ease — for instance, they can climb or descend stairs. They may even perform tasks like preparing and eating a snack. They do not remember the incident later.
Petit said sleepwalkers can get hurt on occasion. She noted there have been reports of children dying of hypothermia after leaving their homes in winter and falling back into a deeper sleep in the snow.
Petit said it's recommended that parents consider an alarm for doors if children who sleepwalk tend to leave the house.
Sleepwalking is more common among children than adults. The research was designed to estimate how common sleep terrors and sleepwalking are among children, to look for links between the two behaviours and to see if they ran in families.
The researchers followed 1,940 children in Quebec from the ages of 1 1/2 or 2 1/2 to 13. Parents were asked annually whether their children experienced sleep terrors and sleepwalking, and whether they had a history of sleepwalking.
Sleep terrors were common, with about 56 per cent of children experiencing this sleep disturbance at some point during the study period. They are most common at younger ages; 34 per cent of 18-month-old kids were reported to have sleep terrors. But the number drops as children get older, with 13 per cent experiencing night terrors at age five and only five per cent at age 13.
Petit said she believes these figures may be too high, noting some parents may confuse nightmares with sleep terrors.
The confusion is understandable. Both may cause a sleeper to cry out, scream or thrash about in bed. But a child having a nightmare will want to be cuddled and reassured when awakened from the dream. A child experiencing sleep terrors may not fully awaken and will become more agitated if hugged; he or she may interpret the touch as being part of the frightening scenario playing out in their brain.
Nightmares typically happen during the middle or late portion of the night. Sleep terrors often happen early in the sleeping period, generally during the first third of the night.
The pattern of sleepwalking rises through childhood; it is uncommon in young children but increases with age. In the study, the peak time for sleepwalking was between the ages of 10 and 13, with just over 13 per cent of children reported as occasionally sleepwalking.
The behaviours appear to be linked. At least a third of the children who had sleep terrors went on to be sleepwalkers.
"More and more it's the accepted idea that they're part of the same condition," Petit said.
These sleep disturbances are known to be triggered by fatigue, sleep deprivation and fevers.