The significant variables associated with ICD development were sex (OR 2.61; CI 1.26–5.39, p = 0.009), age at PD onset (OR 0.96; CI 0.93–0.99, p = 0.013), DRD4 7+ polymorphism (OR 2.23; CI 1.13–4.42, p = 0.021), and presence of dyskinesias (OR 2.31; CI 1.18–4.53, p = 0.015). This evidence concerns the gene DRD4 and Parkinson disease.