COMT and Parkinson disease: As shown in Table 3, non-smokers with at least one A allele of COMT rs4680 (adjusted OR = 3.97, 95% CI = 2.13 - 7.41) had a higher risk of PD than those with the GG genotype (adjusted OR = 3.70, 95% CI = 1.95 - 7.02), relative to ever smokers with the GG (non-risk) genotype (reference).