We read with interest the recent article by Avorn et al.1 Sudden onset of somnolence/sleep (SOS) is an important clinical problem in Parkinson disease (PD) and remains an area of significant controversy. This study identifies dopamine agonists as increasing the risk of SOS in a large sample of tertiary care PD patients. The findings of the study are interesting and confirm previous reports of a higher risk of SOS associated with dopamine agonist therapy relative to levodopa and other antiparkinsonian drugs.2,3