Reproductive factors and Parkinson's disease: A multicenter case-control study

ABSTRACT Background: Given the overlap between Parkinson’s disease and essential tremor, we examined genetic variants in a-synuclein (SNCA) as risk determinants for essential tremor. Methods: Samples from 661 essential tremor subjects and 1316 control subjects from 4 participating North American sites were included in this study. Parkinson’s disease samples (n 5 427) were compared against controls. Twenty variants were selected for association analysis within the SNCA locus. Individual logistic regression analyses against essential tremor diagnosis were run for each variant and then combined using meta-analysis. Results: Our results do not show a significant association between variants in the SNCA locus and risk of essential tremor, whereas the established association of SNCA variants with Parkinson’s disease risk was observed. Conclusions: Whereas genetic factors are likely to play a large role in essential tremor pathogenesis, our results do not support a role for common SNCA genetic variants in risk for essential tremor.