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Patients with early Parkinson's disease were more likely to have a movement disorder called leg motor restlessness than true restless legs syndrome, researchers found.

Although restless legs syndrome was not significantly more common in Parkinson's patients, leg motor restlessness was almost three times more common than in controls, Michaela D. Gjerstad, PhD, of Stavanger University Hospital in Norway, and colleagues reported online in Neurology.

In restless legs syndrome people have an urge to move their legs to stop uncomfortable sensations. The urge occurs at rest, in the evening, and is temporarily relieved by movement.

People with leg motor restlessness also have an urge to move their legs to stop uncomfortable sensations, but it is either not worse when they are at rest or in the evening and it does not go away when they move their legs.

There have been problems with earlier studies of the condition, the researchers wrote. Either study populations included patients with more advanced Parkinson's disease or patients with ongoing dopaminergic treatment, which may have caused underestimation.

For their study, Gjerstad and colleagues included 200 treatment-naive Caucasian early Parkinson's patients derived from a population-based incident cohort and 173 age- and gender-matched controls without Parkinson's disease.

All were assessed for leg restlessness by structured interviews, clinical examination, and blood samples. True restless legs syndrome was diagnosed according to essential diagnostic criteria and was found not more common in people with Parkinson's than among those without the disease.

More patients (81 or 40.5%) than controls (31 or 17.9%) reported leg restlessness (P<0.001); 31 of these patients with Parkinson's (15.5%) and 16 controls (9.2%) met the restless legs syndrome criteria (P=0.07).

After exclusion of potential restless legs syndrome mimics, Parkinson's patients had a relative risk for restless legs syndrome of 1.76 (95% CI 0.90 to 3.43, P=0.089) and 2.84 for leg motor restlessness (95% CI 1.43 to 5.61, P=0.001).

Except for increased sleep disturbances among patients with restless legs syndrome and increased Montgomery and Asberg Depression Rating Scale scores for patients with either disorder, there were no other major differences in relevant blood tests or motor or cognitive function between Parkinson's patients with and without restless legs or leg motor restlessness.

The findings underline a need for more accurate assessments of restless legs syndrome in Parkinson's disease, the researchers noted. However, they wrote, it is possible that people who have not yet taken dopamine for Parkinson's have a dopamine deficiency in their brains similar to the motor restlessness after taking drugs that block dopamine in the brain.

A study limitation included the subjective nature of leg restlessness and the diagnosis of restless legs syndrome based solely on self-reported information.

Restless legs syndrome is an important complaint for Parkinson's patients with increased nighttime sleeping problems and daytime distress. Further studies are needed to better define the concepts of the two disorders in Parkinson's and to identify the relationship between them, the researchers concluded.

In a related editorial, Isabelle Arnulf, MD, PhD, of the Pierre and Marie Curie University in Paris, and John Morgan, MD, PhD, of the Georgia Health Sciences University in Augusta, Ga., wrote that further studies of this cohort will be interesting.

Time will tell, they wrote, whether leg motor restlessness improves with dopaminergic therapy, or, on the contrary, whether some patients without restless legs syndrome or with leg restlessness develop full-blown restless legs syndrome.

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