Supplementary Material for: An Exploratory Study on the <i>CHRNA3-CHRNA5-CHRNB4 </i>Cluster, Smoking, and Parkinson’s Disease

<i>Background:</i> Smokers have a lower risk of Parkinson’s disease (PD). Recent genome-wide association studies (GWAS) have consistently linked several single nucleotide polymorphisms (SNPs) in the <i>CHRNA3-CHRNA5-CHRNB4</i> cluster on chromosome 15.q25 to smoking behaviors and nicotine dependence. Investigations into these SNPs may help explain the nature and mechanisms of the smoking-PD relationship. <i>Objective:</i> To examine whether the genetic variations that were consistently associated with smoking or nicotine dependence in recent GWAS also predict the risk of PD. <i>Methods:</i> This is a population-based case-control study of 788 physician-diagnosed PD patients and 911 controls, all non-Hispanic Whites. Seven SNPs were selected based on findings from recent GWAS on smoking and nicotine dependence, all from the nicotinic acetylcholine receptor subunits <i>(CHRN)</i> A3-A5-B4. Odds ratios (ORs) and 95% confidence intervals were derived from logistic regression models under the assumption of logit-additive allelic effects. <i>Results:</i> Four SNPs in linkage disequilibrium from the <i>CHRNA3-CHRNA5-CHRNB4</i> cluster were associated with smoking duration (OR >1.3, p < 0.05). However, none of the SNPs from this cluster was associated with PD risk in the overall analysis or after stratifying on smoking status. <i>Conclusion:</i> This preliminary analysis does not support a relationship between these smoking-related GWAS SNPs and PD.