title: Rapid Eye Movement Sleep Behavior Disorder Symptoms Correlate with Domains of Cognitive Impairment in Parkinson's Disease.
abstract: BACKGROUND
  Rapid eye movement (REM) sleep behavior disorder (RBD) may be a risk factor for cognitive impairment in patients with Parkinson's disease (PD). However, little is known regarding the relation between the severity of RBD and the different domains of cognitive impairment. The aim of this study was: (1) to investigate the domains of cognitive impairment in patients with PD and RBD, and (2) to explore risk factors for PD-mild cognitive impairment (PD-MCI) and the relationship between RBD severity and impairment in different cognitive domains in PD.
  
  
  METHODS
  The participants were grouped as follows: PD without RBD (PD-RBD; n = 42), PD with RBD (PD + RBD; n = 32), idiopathic RBD (iRBD; n = 15), and healthy controls (HCs; n = 36). All participants completed a battery of neuropsychological assessment of attention and working memory, executive function, language, memory, and visuospatial function. The information of basic demographics, diseases and medication history, and motor and nonmotor manifestations was obtained and compared between PD-RBD and PD + RBD groups. Particular attention was paid to the severity of RBD assessed by the RBD Questionnaire-Hong Kong (RBDQ-HK) and the RBD Screening Questionnaire (RBDSQ), then we further examined associations between the severity of RBD symptoms and cognitive levels via correlation analysis.
  
  
  RESULTS
  Compared to PD-RBD subjects, PD + RBD patients were more likely to have olfactory dysfunction and their Epworth Sleepiness Scale scores were higher (P < 0.05). During neuropsychological testing, PD + RBD patients performed worse than PD-RBD patients, including delayed memory function, especially. The MCI rates were 33%, 63%, 33%, and 8% for PD-RBD, PD + RBD, iRBD, and HC groups, respectively. RBD was an important factor for the PD-MCI variance (odds ratio = 5.204, P = 0.018). During correlation analysis, higher RBDSQ and RBDQ-HK scores were significantly associated with poorer performance on the Trail Making Test-B (errors) and Auditory Verbal Learning Test (delayed recall) and higher RBD-HK scores were also associated with Rey-Osterrieth complex figure (copy) results.
  
  
  CONCLUSIONS
  When PD-RBD and PD + RBD patients have equivalent motor symptoms, PD + RBD patients still have more olfactory dysfunction and worse daytime somnolence. RBD is an important risk factor for MCI, including delayed memory. Deficits in executive function, verbal delayed memory, and visuospatial function were consistently associated with more severe RBD symptoms.
authors.forename: Jin-Ru
authors.initials: JR
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Zi-Jiao
authors.initials: ZJ
authors.lastname: Yang
authors.forename: Hui-Jun
authors.initials: HJ
authors.lastname: Zhang
authors.forename: Yun-Ting
authors.initials: YT
authors.lastname: Fu
authors.forename: Yun
authors.initials: Y
authors.lastname: Shen
authors.forename: Pei-Cheng
authors.initials: PC
authors.lastname: He
authors.forename: Cheng-Jie
authors.initials: CJ
authors.lastname: Mao
authors.affiliation: Department of Neurology and Sleep Center, The Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215004; Institute of Neuroscience, Soochow University, Suzhou, Jiangsu 215123; Beijing Key Laboratory for Parkinson's Disease, Beijing 100053, China.
authors.forename: Chun-Feng
authors.initials: CF
authors.lastname: Liu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D060825:Cognitive Dysfunction / Q000209:etiology*; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications*; D020187:REM Sleep Behavior Disorder / Q000150:complications*