Omoto S, Murakami H, Shiraishi T, et al. - In Parkinson disease (PD), there have been reports of minor hallucinations (MHs), including sense of presence, passage hallucinations, and visual illusions. According to appearance time, researchers here examined the prevalence and associated risk factors for MHs. Using a questionnaire, they obtained data on the clinical features and the appearance time of MHs for 100 PD patients. Based on the time when MHs appeared, they classified MHs into two groups: MHs appearing while awake during the daytime (dMHs) and MHs appearing when patients are aroused from sleep during the night or early morning (aMHs). MHs were reported in 38 patients (38%). Twenty-one (21%) and 28 patients (28%) experienced dMHs and aMHs, respectively. Patients with dMHs relative to patients without MHs were reported to have more severe motor symptoms, longer disease duration, higher levodopa equivalent daily dose (LEDD), higher rate of cognitive impairment, and visual hallucinations during the daytime. Patients with aMHs were reported to have a higher rate of rapid eye movement sleep behavior disorder (RBD), longer disease duration, higher LEDD, and higher dopamine agonist dosage. In logistic regression analysis, there appeared a significant correlation between cognitive impairment and dMHs, and a significant association of rapid eye movement sleep behavior disorder and LEDD with aMHs.