Contrary to previous findings, a new study hints that restless legs syndrome, or RLS, is not more common in people with early Parkinson's disease.
Because the night-time involuntary jerking and flexing is sometimes treated with the same type of drugs as Parkinson's, researchers have wondered if they're related, as some reports have suggested.
The new study found that RLS itself wasn't linked with the movement disorder. Instead, other types of leg restlessness, that happened during the daytime as well, were more common in people just starting to show Parkinson's symptoms.
"The real takeaway is, restless legs syndrome is not more prevalent in patients with early Parkinson's disease than in the general population," said Michaela Gjerstad, from the Stavanger University Hospital in Norway, who worked on the study.
The strange condition, which remains controversial, causes unpleasant sensations in the legs when a person is at rest, triggering an uncontrollable urge to move the legs to get relief. Its exact cause is unknown.
General urges to move the legs could be a part of early Parkinson's, Gjerstad told Reuters Health, and may get better with treatment.
But, she added, when patients with Parkinson's complain of having restless legs, doctors should also look into whether other types of medication (such as antidepressants), lower back pain or iron deficiency might be to blame.
Her study included 200 Norwegians with recently diagnosed Parkinson's, who weren't on medication for the disease, and another 173 people of similar ages without Parkinson's. They were interviewed by neurologists and nurses about their sleep problems, including whether they had symptoms of RLS.
Four in every ten Parkinson's patients, compared to less than two in ten controls, said they had some sort of leg restlessness at night or during the day.
But when the researchers looked for people who met the criteria for an RLS diagnosis, it wasn't any more common among Parkinson's patients.
General leg restlessness that didn't qualify as RLS, however, was reported by more than twice as many people with Parkinson's disease as without. Thirteen percent of Parkinson's patients had those symptoms, compared to less than six percent of the comparison group, Gjerstad and her colleagues reported Wednesday in the journal Neurology.
RLS has been heavily promoted in disease-awareness campaigns. But the phenomenon generally isn't thought to signal a serious medical condition, and some experts view the campaigns as little more than disease-mongering. Among the general population, symptoms may go away with lifestyle changes, such as relaxation, exercise, getting enough iron and avoiding caffeine.
Still, previous studies have suggested that RLS occurs up to five times as often in people with Parkinson's disease, Gjerstad said, and may be linked to low dopamine levels. Drugs called dopamine agonists are sometimes prescribed for both RLS and Parkinson's independently.
Dr. Xiang Gao, who studies both conditions at Harvard Medical School in Boston, said the findings should be "put in the bigger context of all published literature on this topic." That evidence generally does suggest a link between Parkinson's and RLS, he said.
"I think their conclusion is too strong, based on this small sample size," he told Reuters Health, adding that the study also didn't take into account other aspects of health and lifestyle that may affect risk of RLS and Parkinson's differently, including weight and caffeine intake.
Still, Gao said it does bring up the interesting question of whether other types of leg restlessness may be more common with Parkinson's as well. Future studies are needed to better understand that link and what it means for people with restless legs, he added.