title: Progression of cognitive impairments in idiopathic REM sleep behaviour disorder.
abstract: Idiopathic REM (rapid eye movement) sleep behaviour disorder (iRBD) has been implicated in cognitive impairments, but there is little evidence about progression of cognitive dysfunction in iRBD.
  
  
  
  A retrospective follow-up study with patients with iRBD was performed. Conversion to neurodegenerative disorders was analysed by Kaplan-Meier survival analysis. Neuropsychological test results at baseline were compared between patients with iRBD and healthy controls. 57 patients with iRBD were successfully followed up for changes of cognitive performance over time (follow-up duration 50.84±25.38 months; range 12-108 months). Factors affecting cognitive decline were evaluated with multiple regression analysis and the subgroup analysis for groups with and without conversion was carried out.
  
  
  
  Among 84 patients with iRBD, conversion occurred in 18 patients and conversion rates were estimated to be 9%, 18% and 35% at 3, 5 and 6 years from diagnosis of iRBD. Individuals with iRBD showed lower z-scores at baseline than controls in Mini-Mental Status Examination, Trail Making Test A, constructional praxis and Executive Clock Drawing Task (CLOX2). Patients with non-converting iRBD showed significant performance decline in memory (p=0.003, Digit span forward) and a worsening tendency of executive functions (p=0.007, frontal assessment battery; p=0.012, Stroop test) at follow-up tests. Cognitive decline was associated with disease duration or follow-up duration, and lower executive function at baseline increased conversion risk (p=0.031).
  
  
  
  Patients with iRBD have cognitive impairments at baseline and progressive cognitive decline over time. Even in idiopathic cases without development of any neurodegenerative disease, degenerative changes in cognition seem to be under way.
authors.affiliation: Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea.
authors.forename: Soyoung
authors.initials: S
authors.lastname: Youn
authors.affiliation: Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea Department of Psychiatry, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
authors.forename: Tae
authors.initials: T
authors.lastname: Kim
authors.affiliation: Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea Department of Psychiatry, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: In-Young
authors.initials: IY
authors.lastname: Yoon
authors.affiliation: Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea.
authors.forename: Jahyun
authors.initials: J
authors.lastname: Jeong
authors.affiliation: Department of Psychiatry, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Hye Young
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea.
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Han
authors.affiliation: Department of Neurology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jong-Min
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea Department of Psychiatry, Seoul National University College of Medicine, Seoul, Korea Department of Brain and Cognitive Science, Seoul National University College of Natural Sciences, Seoul, Korea.
authors.forename: Ki Woong
authors.initials: KW
authors.lastname: Kim
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000150:complications* / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D018450:Disease Progression; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D019636:Neurodegenerative Diseases / Q000150:complications / Q000175:diagnosis; D009483:Neuropsychological Tests; D020187:REM Sleep Behavior Disorder / Q000150:complications* / Q000523:psychology*; D012189:Retrospective Studies; D012307:Risk Factors