Medical Research:Sleepwalking linked to genetics

Dr. Jacques Montplaisir, of the Hopital du Sacre-Coeur de Montreal in Canada, and colleagues also found a smaller association between parental history of sleepwalking and increased risk of sleep terrors among offspring.

The researchers publish their findings in the journalJAMA Pediatrics.

Sleepwalking is most common in childhood, particularly between the ages of 3 and 7 years, while sleep terrors - episodes of screaming, flailing and intense fear during sleep - often occur between the ages of 4 and 12 years.

While both disorders - known as parasomnias - often wane during adolescence, they can sometimes persist or appear in adulthood, particularly sleepwalking. It is estimated that around 4% of adults in the US sleepwalk.

For their study, Dr. Montplaisir and colleagues set out to assess the prevalence of sleepwalking and night terrors in childhood, to determine whether there is any link between the two conditions later in childhood, and to establish whether a parental history of sleepwalking influences a child's risk of sleepwalking or sleep terrors.

The team analyzed sleep data from 1,940 children who were a part of the Quebec Longitudinal Study of Child Development. The children were born in 1997 and 1998 and studied between 1999 and 2011.

The prevalence of sleepwalking and sleep terrors among the children was assessed annually from the ages of 1.5 and 2.5 years until the age of 13 through a questionnaire completed by their mothers, who were also required to provide information on parental history of sleepwalking.

'Parents who have sleepwalked in the past can expect their children to sleepwalk'

Between the ages of 1.5 and 13 years, the overall prevalence of sleep terrors among the children was 56.2%. While 34.4% of children experienced sleep terrors at the age of 1.5 years, this reduced to 5.3% by the age of 13.

The overall childhood prevalence of sleepwalking between the ages of 2.5 and 13 years was 29.1%. The team reports that the rate of sleepwalking was relatively infrequent during preschool age, but steadily rose to 13.4% by the age of 10 years.

The results of the study revealed a significant link between early incidence of sleep terrors and later development of sleepwalking; 34.4% of children who had sleep terrors between the ages of 1.5 and 3.5 experienced sleepwalking at age 5 and older, compared with 21.7% of children who had no sleep terrors in early childhood.

What is more, the findings revealed that a parental history of sleepwalking was associated with increased risk of sleepwalking among offspring.

Children who had one parent with a history of sleepwalking were three times more likely to sleepwalk themselves than those without a sleepwalking parent, while children whose parents both had a history of the disorder were seven times more likely to sleepwalk.

The researchers also found that children whose parents had a history of sleepwalking were almost twice as likely to experience persistent sleep terrors - defined as onset of night terrors before the age of 4 that continued until after the age of 5.

Commenting on their results, the researchers say:

"These findings point to a strong genetic influence on sleepwalking and, to a lesser degree, sleep terrors. This effect may occur through polymorphisms in the genes involved in slow-wave sleep generation or sleep depth.

Parents who have been sleepwalkers in the past, particularly in cases where both parents have been sleepwalkers, can expect their children to sleepwalk and thus should prepare adequately."

The authors say the study does have some limitations. For example, incidence of sleepwalking and sleep terrors among the children was reported by parents rather than through clinical or objective sleep laboratory assessments.

"Although recognizing sleepwalking is usually not difficult for parents, the identification of sleep terrors can be more problematic," they note. "Our questionnaire contained an operational definition for sleep terrors, but it is nevertheless possible that some parents mistook nightmares for sleep terrors and vice versa."

In September 2014, Medical News Today reported on a study published in the journal Pediatrics, in which researchers found children who are bullied between the ages of 8 and 10 are more likely to experience sleepwalking, sleep terrors or nightmares aged 12.