People who sleepwalk can now blame the disorder on their family.
A study involving a four-generation family of sleepwalkers has suggested a genetic link to the common disorder, according to Washington University School of Medicine researchers.
Sleepwalking occurs in about 20 percent to 25 percent of children and generally resolves by the teen years, but can continue into adulthood. Those with the disorder generally walk during slow-wave sleep, the stage of deepest sleep.
Christina A. Gurnett, MD, PhD, assistant professor of neurology, and her team took DNA samples from 22 members of a family with nine sleepwalkers. The Caucasian family included a child who had been sleepwalking since age 6 and eight other family members who had been sleepwalking since childhood, though less frequently as adults. The sleepwalkers all had more than one sleepwalking episode per month for more than six months. Seven of the affected family members were male, and all but two were over 18 years old.
Gurnett’s genetic screen of DNA from family members found a group of markers on chromosome 20 that were common to all nine of the family members who sleepwalked. This region of chromosome 20 has about 28 known or predicted genes.
“We suspect that one or more of the genes in this region can increase the risk of sleepwalking,” Gurnett says.
Gurnett and the team speculate that the adenosine deaminase gene (ADA) may be the most likely candidate gene on chromosome 20 because of its association with slow-wave sleep. However, one or more of the other candidate genes in the region may also play a role, she says.
The team has already sequenced 10 of these genes and is now sequencing the remainder looking for either common or rare variants. The researchers also have identified additional families of sleepwalkers that they plan to study to determine whether the same DNA variations are present in those sleepwalkers.
“Sleepwalking is not an area that has been well studied in the past, so we may be able to better understand how the brain functions during sleep and what genes are important for normal sleep by doing this research,” Gurnett says. “A secondary goal is to identify better therapies for sleep disorders including sleepwalking.”
There are medications that can be used to limit or reduce the number of sleepwalking episodes, but patients generally don’t seek or need treatment, Gurnett says.
The findings, published in the journal Neurology, may also indirectly help with the treatment of another common sleep disorder – insomnia.
“One of the side effects of commonly used prescription medications for insomnia is sleepwalking,” Gurnett says. “Pharmaceutical companies are interested in understanding the pathways that control abnormal movements in sleep, so we have the potential to improve many therapies for sleep if we can understand sleepwalking better.”
Licis AK, Desruisseau DM, Yamada KA, Duntley SP, Gurnett CA. Novel genetic findings in an extended family pedigree with sleepwalking. Neurology, Jan. 4, 2011, pp. 49-52.