UCHL1 and Parkinson disease: Under a recessive model, compared with subjects with the CC or CA genotype of UCHL1  S18Y SNP, those with the AA genotype had a significantly increased risk of sporadic PD after adjustment for sex, age, region of residence, smoking, and caffeine intake: the adjusted OR was 1.57 (95 % CI: 1.06 − 2.31) (Table 2).