Genetic and environmental risk factors and their interactions for Parkinson's disease in a Chinese population.

The interaction between genetic and environmental factors for PD was examined in a Chinese population. It was found that although the intron 2 MAOB (GT)(n) repeat polymorphism was not associated with PD in the population, a relationship might have been masked by the "protective effect" of tea drinking. In individuals who did not drink tea (<1 cup/day), the possession of short length < or = 178 bp (GT)(n) alleles conferred a borderline significant increased risk for PD (adjusted OR=1.47; C.I.=1.03-2.1). As the extent of tea consumption increased, the association between the < or = 178 bp allele and PD disappeared. This result suggests that the MAOB gene may be associated with PD in Chinese if the putative protective effect of tea drinking is taken into account. The significance of this finding is unclear as the study may be limited because of its marginal significance and limited numbers. However, it does demonstrate the importance of considering putative positive and negative environmental risk factors in any examination of genetic risk factors for PD.