Lack of association between UCHL1 S18Y gene polymorphism and Parkinson's disease in the Asian population: a meta-analysis.

Although many case-control studies have investigated the association between a single UCHL1 S18Y gene polymorphism and the risk of Parkinson's disease (PD), the results have been ambiguous. To evaluate the overall effect between published case-control studies of Asian subjects, we conducted a meta-analysis based on 11 studies including 3,971 PD cases and 3,721 controls. Studies carried out up to 30 April 2014, were identified using the databases PubMed, MEDLINE, EMBASE and Web of Knowledge. The crude odds ratios (ORs) with 95 % confidence intervals (95 % CI) were calculated to evaluate the association. The results of our meta-analysis indicated that the UCHL1 S18Y gene polymorphism does not correlate with the risk of PD (allele model: OR 0.93, 95 % CI 0.84-1.02; dominant model: OR 0.94, 95 % CI 0.86-1.04; recessive model: OR 0.90, 95 % CI 0.77-1.06; homozygous model: OR 0.86, 95 % CI 0.71-1.04). A similar result was observed in subgroup analysis of ethnicity, age at onset, genotype methods, Hardy-Weinberg equilibrium, and source of controls. Thus, the current meta-analysis suggests no evidence for the association between the UCHL1 S18Y polymorphism and PD risk in the Asian population, especially in subgroups of ethnicity and age at onset. Further studies with larger population sizes are needed to confirm this result.