α-Synuclein, alcohol use disorders, and Parkinson disease: A case-control study

Collaborative pooled analyses demonstrated that allele length variability of the dinucleotide repeat sequence within the alpha-synuclein gene promoter (SNCA REP1) is associated with Parkinson disease (PD) worldwide. Other studies demonstrated that variability in the SNCA promoter is also associated with alcohol use disorders, but not consistently. Yet other studies demonstrated that alcohol use disorders are inversely associated with PD, but not consistently. The aim of this study was to clarify the patterns of association between REPI genotype, alcohol use disorders, and PD. Cases were recruited from the Department of Neurology of the Mayo Clinic in Rochester, MN. The controls included unaffected siblings and unrelated controls. We assessed alcohol use via a structured telephone interview and screened for alcohol use disorders using the CAGE questionnaire. REPI genotyping was performed using an ABI 3730XL platform. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined using conditional logistic regression models. We recruited 893 case-control pairs. There was an increasing risk of PD with increasing SNCA REPI allele length (OR 1.18 for each REPI genotype score unit, 95% CI 1.02-1.35; p = 0.02). There was a decreasing risk of PD with increasing CAGE score (p = 0.01). The association of REP1 score with PD remained significant after adjusting for CAGE score, and the association of CAGE score with PD remained significant after adjusting for REPI score. There were no pairwise interactions. Our findings suggest that SNCA REPI genotype and alcohol use disorders are independently associated with PD. (C) 2008 Elsevier Ltd. All rights reserved.