ADORA2A and Parkinson disease: In view of the former considerations, namely certain genetic factors strongly predispose to PD, ADORA2A rs5760423 and CYP1A2 rs762551 polymorphisms may influence the risk of PD and previous studies examining the effect of these polymorphisms to PD have produced inconsistent results, the objective of the current study was to examine the possible crude association of ADORA2A rs5760423 and CYP1A2 rs762551 variants with PD, by performing a case–control study and a cumulative meta-analysis by merging our data with relevant data from previous studies.