"It is not a gene per se for RLS, but rather for leg movements seen in individuals and families with RLS," said Dr. John Winkelman, medical director of the Sleep Health Center at Brigham and Women's Hospital. "Whether the same gene is associated with periodic leg movements in [other] contexts, we have no information from this study."
So essentially what researchers found was a gene for kicking while asleep. This version of the gene was most often found in people who had sleep-kicking problems and didn't have restless legs syndrome.
Moreover, people who had RLS and didn't kick in their sleep were no more likely to have this form of the gene than anyone else in the general population.
About half of patients with RLS are said to have family members who also show symptoms, which has led many to believe heredity plays a role.
In fact, Kaiser said that her son also experiences symptoms of the disorder. And he isn't the only one.
"In the two weeks that we were with my grandmother before she passed, I got to see 19 of my relatives -- and 13 of us had symptoms in one form or another," Kaiser said.
"I wanted to know if there was a genetic link -- if mine was inherited and that's why it was so severe, and undoubtedly that has something to do with it."
In a separate study published this Wednesday in Nature Genetics, a group of German and Canadian researchers found three genes that were associated with symptoms of RLS. One of these is the same gene found by the researchers at deCODE and Emory.
The researchers did not make any claims as to which specific symptoms were influenced by the genes, but in one of the groups they studied, 82.1 percent of their patients who had RLS also had periodic limb movements in sleep.
The New England Journal of Medicine study had a secondary finding that people with this gene variant were likely to have less iron in their blood.
"Iron has important roles in the brain," said Winkelman. Iron is involved in making and using a chemical in the brain called dopamine, which helps brain cells communicate with one another.
"Dopamine is intimately involved with both sensation as well as movement," he said. "And it's probably not a coincidence that the medications that are most effective in treating RLS increase dopamine activity in the brain."
Indeed, the two most prominent drugs to treat RLS are GlaxoSmithKline's Requip and Boehringer Ingelheim's Mirapex. Both medications affect dopamine in the brain and were originally created to help patients with Parkinson's disease, a devastating movement disorder.
"They sell more Requip for restless leg than for Parkinson's. It's taken over the primary indication for why the drug was made, and that speaks for itself," said Emory's Dr. Rye.
This has led many to question the need for so many people to be on medication for RLS.
"There are people whose lives are seriously affected, but those cases are rare," said Dr. Steve Woloshin, senior research associate at the VA Outcomes Group in Vermont who wrote about RLS and disease mongering in PLoS Medicine last year.
"The paper underscores that the marketing of RLS is way ahead of the science," he said. "It seems a little crazy to launch a $27 million campaign to push RLS into America's consciousness when we don't really understand what it is, who has it, or how to decide if or when medication is needed."
For RLS sufferer Kaiser, for whom these medications no longer work, living with RLS and PLMs requires her to take life one day at a time. And through it all, her husband, Bruce, is still by her side.
"We don't go to the number of parties or functions that we used to -- but I love her madly, so to me, it is what it is."
Dr. Rye has reported receiving consulting and lecture fees from Boehringer Ingelheim and GlaxoSmithKline. With respect to deCODE Genetics, Dr. Stefansson has a financial interest in the diagnostic products and patents that may result from this study. Dr. Winkelman has reported receiving financial support for research, as well as consulting and lecture fees, from Boehringer Ingelheim and GlaxoSmithKline. Dr. Woloshin has declared no conflicts of interest.