Prevalence and timeline of nonmotor symptoms in idiopathic rapid eye movement sleep behavior disorder

Parkinson disease (PD) patients may experience nonmotor symptoms (NMS) before Parkinsonism onset. Patients with idiopathic REM sleep behavior disorder (IRBD) eventually develop PD and may represent premotor PD. We aimed to evaluate the prevalence and perceived timeline of NMS in IRBD through validated scales and questionnaires used in PD research. In 44 IRBD patients and 40 matched controls, overall NMS evaluation was assessed by NMS questionnaire for Parkinson disease, olfaction by University of Pennsylvania Smell Identification Test, dysautonomia by scales for outcomes in Parkinson's disease-autonomic, constipation by Rome III criteria, depression by Hospital Anxiety and Depression Scale, cognitive impairment by Montreal cognitive assessment (MoCA) and hypersomnia by Epworth Sleepiness Scale. Patients were asked to report the perceived time of onset of hyposmia, constipation, and depression. Hyposmia (52.3 vs. 20.0 %, p = 0.002) and constipation (56.8 vs. 20.0 %, p = 0.001) were more frequent in patients than in controls. Patients reported more memory problems and showed a trend toward lower score in MoCA. Depression and hypersomnia were not more frequent in patients. The first symptom perceived was RBD in 38.6 % patients, hyposmia in 15.9 %, constipation in 11.4 %, and depression in 6.8 %. The temporal course of the NMS studied was heterogeneous. The three most common presentations were RBD followed by hyposmia; hyposmia followed by RBD; and hyposmia followed by RBD and constipation occurring at the same time span. IRBD patients frequently exhibit NMS that occur in premotor PD, particularly hyposmia and constipation. In IRBD, the perceived timeline of NMS is highly variable. This variability may suggest that pathological changes occurring in IRBD subjects are also heterogeneous and not restricted to the structures that regulate REM sleep.