1. Restless legs syndrome (RLS) was associated with higher Parkinson disease (PD) incidence: 10.1 vs 6.3 per 10,000 patient-years (1.6% vs 1.0% of patients).
2. Among patients with RLS, dopamine agonist exposure correlated with a lower observed PD incidence (0.5% vs 2.0% without dopamine agonists).
3. Time-to-PD diagnosis differences were small overall and directionally varied by dopamine agonist use.
4. The researchers interpret RLS as a potential PD risk factor, with plausible nondopaminergic contributors (noradrenergic pathways, iron deficiency, and sleep disruption).
5. Causal inference is limited by ICD-10–based misclassification (e.g., REM sleep behavior disorder) and the possibility that dopamine agonists mask early parkinsonian symptoms.

Sources:

JAMA Network Open Original Investigation

JAMA Network Open Invited Commentary