A nationwide Korean cohort (2002–2019) of 9,919 patients with restless legs syndrome (RLS) matched to 9,919 controls showed higher Parkinson disease (PD) incidence in RLS: 10.1 vs 6.3 per 10,000 patient-years (1.6% vs 1.0%). Among patients with RLS, dopamine agonist exposure was associated with a lower observed PD incidence (0.5% vs 2.0% without dopamine agonists). Differences in time to PD diagnosis were small. The researchers interpret RLS as a potential PD risk factor involving nondopaminergic mechanisms, but misclassification (e.g., REM sleep behavior disorder) and possible symptom masking by dopamine agonists limit causal inference.
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