The COSP-RBD Study: Concussions and Contact Sports in RBD vs Controls

Inclusion criteria group with RBD: * Patient at the SDC with diagnosis of RBD (Guy's and St Thomas' NHS Foundation Trust). * 50 years of age or above (patients below this age would not be expected to have a RBD related to a synucleinopathy and other causes of RBD would need to be considered instead - e.g. narcolepsy, post-traumatic stress disorder). Inclusion criteria control group: * Patients who have undergone a v-PSG at the SDC (Guy's and St Thomas' NHS Foundation Trust) and who do not have history of suspected RBD or RBD confirmed by v-PSG. * 50 years of age or above This group will be age- and sex-matched to the RBD group. Exclusion criteria group with RBD: * Age \< 50 years of age. * Diagnoses of narcolepsy or post-traumatic stress disorder. * Subjects lacking capacity or literacy. * Non-English speakers. Exclusion criteria control group: * Age \< 50 years of age (in order to match RBD group). * REM sleep without atonia or confirmed RBD on v-PSG. * Diagnosis of neurological diseases, cognitive complaints or motor complaints. * Clinical history suggestive of parasomnia that may be included in the differential of RBD. * Subjects lacking capacity or literacy. * Non-English speakers.