REM sleep behavior disorder (RBD) is a novel type of Parasomnias characterized by abnormal behavioral manifestations during REM sleep . RBD affects 0.4-0.5% of the elderly population with a typical age of onset in 50s-60s . RBD presents with a spectrum of dreamenacting behavioral manifestations, including sleep shouting, fisting, kicking or falling out of bed with a high prevalence of sleep-related injuries to themselves or/and bed-partners. Accumulating evidences suggests that idiopathic RBD (iRBD) is an integrated part of disease progress in α-synucleinopathy neurodegeneration, such as Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) . Longitudinal clinical studies suggests that the estimated 5-year risk of developing any neurodegenerative disorder in iRBD patients range from 8.5%-38%, which increase to 38%-65% at around 10- year follow-up . Hence, the time gap between RBD and neurodegenerative disorders may potentially provide a therapeutic window for neuroprotective measures in halting the underlying neurodegeneration at an early stage. Thus, research also focused on the identification of subclinical markers of neurodegeneration in iRBD, including color vision deficit and olfactory dysfunction, which might be construed as the early stages of neurodegenerative process. Additionally, polysomnographic feature of RBD has also been reported as a predictive marker of neurodegeneration. Nonetheless, studies were limited by cross-sectional design with relatively small sample size.