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Background Increasing evidence supports an extensive and complex genetic contribution to PD. Previous genome‐wide association studies (GWAS) have shed light on the genetic basis of risk for this disease. However, the genetic determinants of PD age at onset are largely unknown. Objectives To identify the genetic determinants of PD age at onset. Methods Using genetic data of 28,568 PD cases, we performed a genome‐wide association study based on PD age at onset. Results We estimated that the heritability of PD age at onset attributed to common genetic variation was ∼0.11, lower than the overall heritability of risk for PD (∼0.27), likely, in part, because of the subjective nature of this measure. We found two genome‐wide significant association signals, one at SNCA and the other a protein‐coding variant in TMEM175, both of which are known PD risk loci and a Bonferroni‐corrected significant effect at other known PD risk loci, GBA, INPP5F/BAG3, FAM47E/SCARB2, and MCCC1. Notably, SNCA, TMEM175, SCARB2, BAG3, and GBA have all been shown to be implicated in α‐synuclein aggregation pathways. Remarkably, other well‐established PD risk loci, such as GCH1 and MAPT, did not show a significant effect on age at onset of PD. Conclusions Overall, we have performed the largest age at onset of PD genome‐wide association studies to date, and our results show that not all PD risk loci influence age at onset with significant differences between risk alleles for age at onset. This provides a compelling picture, both within the context of functional characterization of disease‐linked genetic variability and in defining differences between risk alleles for age at onset, or frank risk for disease. © 2019 International Parkinson and Movement Disorder Society

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Dopamine agonists are used as initial treatment in patients with Parkinson's disease (PD) to reduce incidence and severity of motor complications. This paradigm is based on long-term studies, allowing "rescue" therapy with levodopa. The present strict monotherapy study (PELMOPET, the acronym for the pergolide-versus-L-dopa-monotherapy-and-positron-emission-tomography trial) evaluated the efficacy and safety of pergolide versus levodopa without levodopa "rescue" medication. This multicenter, double-blind, randomized, 3-year trial compared pergolide monotherapy (n=148) with levodopa monotherapy (n=146) in dopamine-naive patients with early PD (Hoehn and Yahr stage 1-2.5). Primary efficacy measures were clinical efficacy, severity and time to onset of motor complications, and disease progression. During the 3 years, severity of motor complications was significantly lower and time to onset of dyskinesia was significantly delayed in the group receiving pergolide (3.23 mg/day) compared with those receiving levodopa (504 mg/day). However, time to onset of motor complications was not longer in patients receiving pergolide after 3 years. Symptomatic relief (assessed by Unified Parkinson's Disease Rating Scale [UPDRS], UPDRS II, and III, Clinical Global Impressions [CGI] severity, and CGI and Patient Global Impressions [PGI] improvement) was significantly greater in patients receiving levodopa. Adverse events led to discontinuation of therapy in 17.6% of pergolide patients and 9.6% of levodopa patients. This is the first study comparing strict monotherapy with a dopamine agonist versus levodopa in previously untreated early PD. In principle, both levodopa and a dopamine agonist such as pergolide seem to be suitable options as initial PD therapy. The choice remains with the treating physician based on the different efficacy and adverse event profiles.