UCHL1 is associated with Parkinson's disease: A case-unaffected sibling and case-unrelated control study

To avoid the possible confounding effect of population stratification, we employed a discordant sibling study design and a liberalization of the sibling transmission disequilibrium test to confirm the association of the S18Y variant of the ubiquitin carboxi-terminal hydrolase L1 (UCHL1) gene with Parkinson's disease (PD). The study included 497 case-control pairs (427 case-unaffected sibling pairs and 70 case-unrelated control pairs). Analyses confirmed a significant inverse association of the UCHL1 S18Y polymorphism with PD overall (OR = 0.18, 95% CI = 0.05-0.64, p = 0.002, recessive model) and in several strata.