Common condition could be key risk factor for Parkinson’s disease: study

Parkinson’s disease — which can cause tremors, slow movement and stiffness — is believed to affect 1 in every 336 Americans.

The exact cause of the neurodegenerative disorder is not known, but it is believed to stem from a combination of genetic and environmental factors.

Now, three hospitals in Korea are reporting that patients with restless legs syndrome are more likely to develop Parkinson’s.

Restless legs syndrome (RLS), also known as Willis-Ekbom disease, is a neurological condition that causes an acute and uncomfortable urge to move the legs.

Movement lessens the pain. Symptoms tend to worsen at night or when sitting or lying down. RLS can develop at any age, but it typically becomes more severe and common with age.

RLS is said to affect at least 3 million Americans, and its symptoms may appear elsewhere on the body, such as the arms or even the face.

Some believe the condition is vastly underreported, as the Restless Legs Syndrome Foundation estimates that 7% to 8% of Americans are living with some form of RLS.

While the exact cause of RLS remains unclear, dopamine therapy has been the standard, first-line treatment.

Dopamine agonists mimic the effects of dopamine, a neurotransmitter that plays a vital role in movement and muscle control.

Similarly, patients with Parkinson’s have reduced dopamine levels. Dopamine agonists are often employed as front-line treatment.

Given their overlapping treatment protocols, researchers are exploring whether the two conditions are triggered by the same dopaminergic mechanisms.

In this latest study, published this week in JAMA Network Open, researchers were keen to determine whether RLS is a risk factor for Parkinson’s and whether the dopamine pathway is relevantly linked to both conditions.

The team used data from over 18,000 patients, half of which suffered from RLS and half of which made up a control group.

The median age was 50, and 62.8% of the participants were women.

Compared to the control group, there was a 60% higher incidence of Parkinson’s in the RLS cohort.

Further analysis revealed that those taking a dopamine agonist had only 0.5% Parkinson’s incidence compared to 2.1% in the nontreated group.

Study authors suggested that RLS may be associated with an increased risk of Parkinson’s, and RLS patients who were not treated with dopamine agonists displayed a higher incidence of Parkinson’s and a significantly shorter time to diagnosis.

Researchers note that these results do not absolutely indicate that dopamine agonists prevent or impede Parkinson’s, but they hint at the possibility that they could have a neuroprotective effect and deserve to be the focus of future research.

The team also notes that the connection between RLS and Parkinson’s could very well go beyond the dopaminergic pathway, and clarifying the pathway’s role will deepen our understanding of the mechanism of both diseases.

Other recent research has established a link between the seemingly harmless human pegivirus — a blood-borne virus from the same family as hepatitis C — and the development of Parkinson’s.