Gene-environment interactions in Parkinson's disease.

PD is the second most common neurodegenerative disease, and affects 5% of the population by the age of 85. PD is a multi-factorial disease with a complex etiology including genetic risk factors, environmental exposure and aging. The pathogenesis is not fully understood. Here we review research on the genetic and environmental causes of PD and the current research models. None of the single models replicate all the features of PD. Genetic models (possibly including more than one mutation) in combination with toxins or other environmental manipulation may provide better models of PD pathogenesis.