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Genetics of sleepwalking

People who sleepwalk can now blame the disorder on their families. 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.

SLEEPWALKING SEEMS TO BE AN INHERITED TRAIT IN SOME PEOPLE, AND WASHINGTON UNIVERSITY RESEARCHERS NOW HAVE IDENTIFIED A SPECIFIC REGION OF DNA AS RELATED TO THE CONDITION IN A FOUR-GENERATION FAMILY OF SLEEPWALKERS. THE RESEARCHERS FOUND THAT THOSE WHO DID SLEEPWALK ALSO HAD SUBTLE DIFFERENCES IN A REGION OF CHROMOSOME 20. JIM DRYDEN REPORTS…

IT’S SOMETIMES DIFFICULT TO KNOW WHETHER OR NOT YOU SLEEPWALK. WASHINGTON UNIVERSITY NEUROLOGIST CHRISTINA GURNETT SAYS SLEEPWALKERS USUALLY DON’T REMEMBER THE EXPERIENCE, SO UNLESS THEY WAKE UP IN A STRANGE PLACE OR SOMEONE ELSE TELLS THEM THEY’VE BEEN SLEEPWALKING, SOME PEOPLE WILL NEVER KNOW THEY WERE. THE BEST ESTIMATES ARE THAT BETWEEN 20 AND 25 PERCENT OF CHILDREN SLEEPWALK, BUT THE PROBLEM USUALLY RESOLVES BY THE TIME THEY ARE TEENAGERS. IN SOME CASES, HOWEVER, THE PROBLEM CAN PERSIST INTO ADULTHOOD. GURNETT TOOK DNA SAMPLES FROM 22 MEMBERS OF A FAMILY WITH 9 SLEEPWALKERS. SEVEN OF THOSE SLEEPWALKERS WERE MALE, AND ALL BUT TWO WERE OVER 18. SHE WAS INTRODUCED TO THE FAMILY WHEN ONE OF THE SLEEPWALKERS WAS REFERRED TO HER FOR PROBLEMS WITH WHAT HAD BEEN DIAGNOSED AS EPILEPSY.

(act) :19 o/c 9 sleepwalkers

It turns out a lot of patients with sleepwalking are misdiagnosed

as having other things. We obtained DNA from all of the family

members and then typed many different markers – 10,000 markers for

each of the 23 individuals – and then found the markers that were

common to each of the 9 sleepwalkers.

GURNETT SAYS FINDING SUCH A BIG GROUP OF SLEEPWALKERS IN A SINGLE FAMILY GIVES MORE POWER TO THIS SORT OF A GENETIC STUDY. AND SHE SAYS IN ANALYZING DNA SAMPLES FROM FAMILY MEMBERS, SHE WAS ABLE TO ISOLATE A SPECIFIC DNA REGION THAT MAY BE RESPONSIBLE.

(act) :15 o/c of sleepwalking

We found a series of markers on chromosome 20 that were common

to all of the affected individuals. And there were, fortunately,

only 30 genes in the region, so we suspect that one of these

genes – or more of the genes in that region – can increase your

risk of sleepwalking.

GURNETT SAYS SHE WAS HEARTENED THAT THE PARTICULAR PART OF CHROMOSOME 20 THAT HER TEAM IDENTIFIED HOUSES SOME LOGICAL CANDIDATES FOR A SLEEPWALKING GENE.

(act) :15 o/c you sleepwalk

There is one gene in there that’s called ADA, or adenosine deaminase,

and this gene has already been linked to differences in the

amount of time that people spend in slow-wave sleep. And slow-wave

sleep happens to be the time when you sleepwalk.

GURNETT’S TEAM IS STILL LOOKING FOR “THE” GENE, OR GENES, THAT MAKE ONE PERSON SLEEPWALK WHEN ANOTHER DOESN’T. SHE’S CONTINUING TO STUDY DNA FROM OTHER FAMILIES OF SLEEPWALKERS, AND TO ANALYZE DNA FROM THE 9 SLEEPWALKERS IN THE FAMILY THAT WAS THE SUBJECT OF THIS STUDY. ACTUALLY, SHE SAYS 9 IS JUST AN ESTIMATE FOR THE NUMBER OF SLEEPWALKERS IN THE FAMILY. PERHAPS, SHE SAYS, THE GENETIC PREDISPOSITION SKIPPED SOME MEMBERS. OR PERHAPS, SHE SAYS, SOME MAY CARRY THE GENETIC PREDISPOSITION BUT EITHER NOT SLEEPWALK, OR NOT REALIZE THAT THEY SLEEPWALK.

(act) :20 o/c individual sleepwalker

Of course, some individuals may not be known to sleepwalk because

no one ever witnessed it. So one of problems of getting this history

from individuals or patients with sleepwalking is that you have to

talk to their parents or to their spouses or whoever might actually

witness them at night. But it can occur without the knowledge of the

individual sleepwalker.

GURNETT REPORTED HER FINDINGS IN THE JOURNAL NEUROLOGY. I’M JIM DRYDEN…

RUNS 2:59