Efficacy of melatonin in rapid eye movement (REM sleep) behaviour disorder with coexisting Parkinsonism

INTERVENTION: Circadin prolonged release tablet 2 mg (prolonged release melatonin 2mg) ‐ 1x2tablets (total of 4mg per day) , orally ingested , after food, within 1 hour bedtime for 8 weeks Total duration of the trial is 16 weeks: 4 weeks of screening period, 8 weeks of treatment period, 4 weeks of followup period. CONDITION: Efficacy of melatonin Parkinsonism REM sleep behaviour disorder PRIMARY OUTCOME: The efficacy of melatonin will be assessed by the difference in the mean of the total number of recorded events of all kinds as captured by the "weekly CIRUS RBD questionnaire" which measures the frequency and the severity of symptoms of REM sleep behaviour disorder. ; Improvement over the last 4 weeks of treatment compared to the 4 weeks prior to treatment whilst including statistical information collected during the intervening period to characterize individual phenotype SECONDARY OUTCOME: A change in the Parkinson’s disease questionnaire (PDQ39),a ; 39‐item questionnaire that measure the health status of PD patients ; A change in the Depression, Anxiety, Stress scales (the DASS): a 42‐item self‐report instrument for measuring depression, anxiety and tension/stress A change in the short form 36 health survey questionnaire (SF‐36),a 36‐item scale measuring eight‐health concepts. It is useful in assessing the health benefits produces by a treatment ; Change in the self‐reported sleepiness (ESS), Comparison of Leeds Sleep Evaluation Questionnaire between melatonin and placebo. The Leeds questionnaire is a side‐effect of hypnotics questionnaire with 4 sub‐scales measured on 10 visual analogue scales Improvement in self‐reported quality of sleep (Pittsburg sleep quality index) Improvement in the index of REM sleep without atonia (RWAI) on a polysomnogram as described by Ferri R. et al. in ; "A quantitative statistical analysis of the submentalis muscle EMG amplitude during sleep in normal controls and patients with REM sleep behavior disorder. Journal of sleep research. 2008;17(1):89‐100". SUB‐ANALYSES. The validity of the weekly CIRUS RBDQ will also be investigated using these clinical trial data. We will correlate aggregate events on the wCIRUS‐RBDQ questionnaire to other potential measures of RBD such as actigraphy, CGI, RWAI. The clinical global improvement impression score The efficacy of melatonin will be assessed by the difference in the mean of the total number and severity of injuries and bedroom environment damage incidents as captured by the "weekly CIRUS RBD questionnaire" which measures the frequency and the severity of symptoms of REM sleep behaviour disorder. ; Improvement over the last 4 weeks of treatment compared to the 4 weeks prior to treatment whilst including statistical information collected during the intervening period to characterize individual phenotype The efficacy of melatonin will be assessed by the difference in the mean of the total number and severity of vivid dreams as captured by the "weekly CIRUS RBD questionnaire" which measures the frequency and the severity of symptoms of REM sleep behaviour disorder. ; Improvement over the last 4 weeks of treatment compared to the 4 weeks prior to treatment whilst including statistical information collected during the intervening period to characterize individual phenotype INCLUSION CRITERIA: 1) Age over 18 2) MiniMental State Examination>/=24 3) REM sleep Behaviour Disorde (RBD)r as defined by the International Classification for Sleep Disorder criteria (ICSD‐2) 4) Screening questionnaire criteria (RBDSQ) with a score equal or greater than 5/13 confirmed by bed partner 5) Two or more events of RBD defined by dream enactment behaviour and/or sleep related injuries (question 2 and 4 of the wCIRUS‐RBDQ) during the 4 weeks (screening period) prior to randomisation. 6) Stable medications for 1 month prior to randomisation.