Familial Aggregation and Biomarkers in REM Sleep Behaviour Disorder: a Case-control Family Study

REM sleep behavior disorder (RBD) is a parasomnia characterized by abnormal behavioral manifestations during REM sleep. Previous case-control studies and prospective studies have documented the progression of α-synucleinopathy neurodegeneration in relation to RBD and have identified some biomarkers of predicting neurodegeneration in patients with iRBD, such as olfactory dysfunction, color vision deficit, autonomic dysfunction, tonic EMG activity during REM sleep, and psychiatric disorder. However, these biomarkers might precede the onset of RBD, as a result, searching for biomarkers for the neurodegeneration before RBD onset is helpful to map the progression of neurodegeneration. In this regard, the investigators aim to study the familial aggregation of RBD and its core features, and compare the differences in major biomarkers of neurodegeneration, including percentage of EMG activity during REM sleep, cognitive functions, autonomic dysfunction, and psychiatric disorders, between unaffected first degree relatives of RBD cases and non-RBD controls.