In addition, the Parkinson’s Epidemiology and Genetics Association Studies in US (PEGASUS) consortium (involving 3000 subjects of five independent well-characterized patient-control series) uncovered an association between an Adora2a variant (rs7165183 and rs5996696) and a reduced risk of PD (Popat et al., 2011), with the strongest coffee-PD association among those with homozygous carriers of the CYP1A2 polymorphisms and slow metabolizers of caffeine. Here, ADORA2A is linked to Parkinson disease.