The previously reported risk factors for OH included male sex, older age, PIGD phenotype, poor gastrointestinal dysfunction, polypharmacy (defined as intake of > 5 medications), and the use of anti-PD drugs (e.g., levodopa, dopamine agonists, and MAO-B inhibitors) (Churchyard et al., 1999; Kujawa et al., 2000; Allcock et al., 2006; Perez-Lloret et al., 2012; Noack et al., 2014; Szewczyk-Krolikowski et al., 2014; Hiorth et al., 2019; Quarracino et al., 2020). The gene discussed is MAOB; the disease is Parkinson disease.