PREdictive Risk Factors of Conversion Into Idiopathic RBD. Italian Study

REM Sleep Behavior Disorder (RBD) is a REM sleep parasomnia first described in 1986 and characterized by the loss of physiological muscle atonia typical of REM sleep and by the presence of abnormal, sometimes violent, motor activity often related to dream content The observed motor behaviors are often associated to vivid dreams, characterized by an aggressive-defensive content, even if pleasant dreams have been described, resulting in non-violent behaviors. Diagnosis of RBD requires video-polysomnographic recording (vPSG) at a Sleep Center, essential to identify and quantify the complete or intermittent loss of physiological muscle atonia during REM sleep (REM sleep without atonia, RSWA) and record any related motor behaviors. The exact prevalence of RBD in the general population is not known and it seems underrated, but is estimated to be 0.3-1.15%. RBD is defined as idiopathic or isolated (iRBD) when it is not associated with other neurological diseases. The so-called symptomatic RBD, on the other hand, can occur in association with neurodegenerative diseases of the spectrum of alpha-synucleinopathies which include Parkinson's Disease (PD), Multiple System Atrophy (AMS), and Lewy Body Dementia (DLB). In recent years, several follow-up studies on large cohorts of iRBD patients have shown that the idiopathic form evolves towards a symptomatic form in most cases. More precisely, the risk of developing an alpha-synucleinopathies increases over time, with a conversion rate of up to 90% in some studies at 14 years. RBD represents an early marker of neurodegeneration, like a unique open window on the initial, pre-symptomatic phase of alpha-synucleinopathies, which could allow the use of neuroprotective therapies, as soon as they are available. Several longitudinal studies indicated older age, presence of hyposmia, abnormal color vision, minimal extrapyramidal motor signs, mild cognitive impairment, autonomic disturbances, and severity of loss of RSWA as risk factors for