Researchers say these cells may become overactive in people with this condition.
It affects 1 in 10 adults and, until recently, the drugs most commonly prescribed for it made the ailment worse over the long run.
For sufferers of restless leg syndrome, an uncontrollable urge to move their legs can constantly interrupt their sleep, if they manage to get to sleep at all.
New drugs have emerged to help treat the condition, but the medications are often borrowed from other conditions and have drawbacks.
Part of the problem with developing better drugs is that researchers don’t yet have a complete picture of why people get restless legs.
“It’s a condition that we know how to fix and we know who has got it, but there’s still a lot of work to be done in terms of figuring out why people get it,” Dr. Nitun Verma, a sleep medicine specialist and spokesman for the American Academy of Sleep Medicine, told Healthline.
That picture was fleshed out a bit more this month.
A new study found that nerve cells in the legs can have heightened excitability in patients with restless legs.
Finding drugs that can target the communication between those cells and bring the signals down to normal levels could be a new way of trying to prevent restless legs.
That can cause those cells to fire out an abnormally high number of signals to each other.
Causes and treatments
A number of factors have been blamed for restless leg syndrome — often called by those who work on it “the most common condition you have never heard of.”
Those causes include genetics, iron deficiency, certain medications and stimulants, an imbalance of chemicals in the brain, and pregnancy.
The symptoms seem to start in the brain, not in the legs.
People can get that uncontrollable, difficult-to-ignore urge to move their legs even if they have lost their legs, said Dr. Mark Buchfuhrer, a sleep specialist at Stanford’s Restless Legs Syndrome Clinic, told Healthline.
So, most treatments for restless legs focus on the brain and are borrowed from other conditions that affect the brain.
Buchfuhrer said four drugs are approved for restless legs, and two of those are in a class of drugs — dopamine agonists — that are given to patients with Parkinson’s disease.
“Those were the go-to drugs 10, 15 years ago,” he said. “But the vast majority of patients using those drugs will get a worsening of restless legs in about 10 years, and it becomes markedly more difficult to treat.”
That worsening, he said, can occur so slowly that physicians may not tie it to the drugs and may prescribe even more of them, which can just make things worse in the long run.
Eventually, patients would need to take low doses of opioids, which have their own well-chronicled problems.
“There’s almost no other disease I know of that taking a medicine to treat the disease makes it worse,” Buchfuhrer said.
Where possible, the new go-to drugs for restless legs are antiseizure medicines used to treat conditions such as epilepsy.
Gabapentin, which goes by the brand name Horizant and others, and pregabalin, which goes by Lyrica, are now sometimes used as even a first-line treatment, said Verma.
They don’t have the worsening risks, but they can’t be used on people who are at risk of falling, such as the elderly. Restless legs symptoms typically get worse with age.
Verma doesn’t think the new study will lead to any new, exciting treatments.
“It just reinforces the meds we’re using,” he said. “It is not like a big doorbusting opening to new options.”
“Once we get that, we can have even more precise meds that target it directly,” he said.
But he said there is a need for better information on why people get restless legs and how those urges occur physiologically.
“There’s not that many new things coming out compared to what there used to be,” Buchfuhrer said. “But there’s a terrific need for new treatments.”
He noted that for some patients, non-pharmaceutical treatments such as a vibration pad or a foot wrap that lightly stimulates the nerves may work.
Mild to moderate regular exercise can be beneficial for some people too, although Buchfuhrer noted that vigorous exercise will make the ailment markedly worse.
“Conservatively, about 2 percent of adults has it bad it enough that treatment would be a strong consideration,” Buchfuhrer said.
For those who have this severe condition, he added, a good night’s sleep would be one to two hours.
“You can’t imagine the suffering of these patients,” he said. “After an hour or two of sleep, they get up and have breakfast and have to eat while walking around because they can’t sit long enough because it will drive them crazy.”
The bottom line
A new study narrows in on a cause of restless leg syndrome.
The condition — which causes an uncontrollable urge to move the legs, especially at night — affects around 10 percent of American adults and is severe enough in at least 2 percent of adults that treatment is required for them to be able to sleep.
But those treatments have been problematic.
New research is needed to pinpoint more precisely how the condition works so more targeted and effective therapies can be developed.