Parkinsons disease (PD) is one of the most common neurodegenerative diseases.Genetic factors are involved in ＜10％ of PD cases,while the majority of PD cases have no identifiable genetic factors.All these studies have revealed the heterogeneity of Parkinsons disease both in pathogenesis and etiology [1,2].In the past decade,many well-designed longitudinal studies have clearly elucidated that environmental or behavioral factors can modify the risk of developing Parkinsons disease and alter the pathological process of PD [2].Moreover,many factors that were found to be associated with an altered risk of PD in epidemiological studies have been confirmed to be neuroprotective or neurotoxic to dopaminergic (DA) neurons in experimental animal models of PD.