COMT and Parkinson disease: The frequency of the COMT rs4680 “GA” and “AA” genotypes (Val/Met heterozygotes and Met/Met homozygotes) was higher in PD patients with pain than pain-free PD patients (46.1% vs. 31.1%, P < 0.01; it remained significant even after Bonferroni correction), and the presence of the “A” allele increased the susceptibility of pain in patients with PD (odds ratio [OR] = 1.70, 95% confidence interval [CI] = 1.24–2.40, P < 0.01).