[Parkinson's disease and environmental factors].

The etiology of the nigrostriatal pathway degeneration in Parkinson's disease (PD) is unknown but there is a growing pool of evidence that environmental factors may be involved in the genesis of this disorder. The discovery of the N-Methyl 4-Phenyl 1,2,3,6-Tetrahydro-Pyridine (MPTP)-induced injury in late 1970s provided the first experimental model of PD and stimulated dramatically the epidemiological research. An excitotoxic amino acid contained in Cycadales, which is thought to be responsible for the amyotrophic lateral sclerosis-parkinsonism-dementia complex of Guam, provides another example of toxin-induced parkinsonism. This amino acid is present in most seeds common in the Western diet. In developed countries, prevalence of PD is 2 to 5 times as high than in developing countries. PD patients in developed countries are more likely than controls to have lived in rural environment. Case control studies have suggested that this positive association is possibly related to pesticides and herbicides exposures or well water drinking. Dietary surveys are now going on and several hypothesis are tested including high MPTP-structural analogs or seeds consumption in PD patients and low antioxidants consumption. The negative association between smoking habits and PD has been recognized for more than 20 years. There is evidence that this association is not an artefact due to the disease affecting smoking habits. Its origin is unknown but it could provide important aetiological clues for PD. The most recent hypothesis concerning the relationships between these environmental factors and PD are reviewed and pertinent suitable surveys for the future are discussed.