Restless Legs Syndrome Associated With Higher Risk for Parkinson Disease
Restless legs syndrome (RLS) was found to be associated with an increased risk of developing Parkinson disease (PD). Further, patients with RLS who were not treated with dopamine agonists (DA) were at an increased risk of PD development, while those who were treated with DAs were at a decreased risk.
Results from the Korean retrospective cohort study were published in JAMA Network Open. The findings “suggest that the pathophysiological connection between RLS and PD may involve mechanisms beyond the dopaminergic pathway.”
“Previous retrospective cross-sectional studies on PD and RLS focused on the presence or absence of RLS symptoms among patients with PD,” wrote Myeonghwan Band, MD, National Health insurance Service Ilsan Hospital, Goyang, Republic of Korea, and co-authors. “These studies have reported that a significant number of patients with PD exhibit RLS symptoms and that patients with PD and RLS experience reduced sleep quality and overall quality of life.”
Researchers utilized data from the Korean National Health Insurance Service Sample Cohort from 2002 to 2019. Patients with RLS and PD were determined using codes from the International Statistical Classification of Disease and Related Health Problems, Tenth Revision and matched to individuals without RLS. For secondary analysis, a DA-treated group was established based on patients with RLS who received DA during 2 or more clinical visits. Those who did not meet this criterion were categorized as the DA-nontreated group.
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A total of 9919 patients with RLS and 9919 matched controls were included in the analysis. Mean (SD) age at enrollment was 50.1 (16.3) years in the control group (6225 women [62.8%]) and 50.3 (16.0) years in the RLS group (6225 women [62.8%]). Incidence of PD was 1.0% (99) in the control group and 1.6% (158) in the RLS group.
To compare time to PD diagnosis across groups, researchers conducted a restricted mean survival time (RMST) analysis. At the prespecified time horizon of 15 years, the RMST to PD diagnosis was 14.93 years in the control group and 14.88 years in the RLS group, marking a difference of –0.05 years (95% CI, --0.07 to –0.03 years). Compared to the control group, the DA-nontreated RLS group (n=6842) displayed a significantly shorter RMST to PD diagnosis (difference, --0.09 years [95% CI, -0.12 to –0.06 years]) and a higher incidence rate (143 of 6842 [2.1%]). The DA-treated RLS group (n=3077) displayed a significantly longer RMST to PD diagnosis (difference, 0.03 years [95% CI, 0.01-0.06 years]) and a lower incidence rate (15 of 3077 [0.5%]).
Authors acknowledged several limitations to the study. Patients with RLS and PD were identified using ICD-10 codes, so there was a possibility of underdiagnosis or overdiagnosis. The study was also not able to confirm a causal relationship or shared dopaminergic pathway dysfunction between RLS and PD, requiring future studies to clarify the association.
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