MAOB and Parkinson disease: Indeed, gender-specific interactions between smoking and genetic polymorphisms of MAO-B intron 13 A/G polymorphism were found to influence PD risk (OR = 0.27, 95% CI [0.13–0.58] for ever-smokers versus never-smokers in men (genotype G), and OR = 1.26, 95% CI [0.60–2.63] for men of genotype A (interaction χ2 = 8.14, p = 0.004)).