title: The combined effect of REM sleep behavior disorder and hyposmia on cognition and motor phenotype in Parkinson's disease.
abstract: BACKGROUND
  Olfactory dysfunction and REM sleep behavior disorder (RBD) are recognized as pre-motor symptoms of Parkinson's disease (PD). Cognitive dysfunction is observed at a high rate even in the early stages of PD as an important non-motor symptom. PD has been classified in different subtypes and it is unknown if olfactory dysfunction and RBD occur more often in one particular subtype. We investigated the relationship between olfactory impairment, RBD, initial cognitive performance and motor phenotype in PD.
  
  
  METHODS
  Nighty-eight patients with drug-naïve idiopathic PD who visited the Movement Disorders Unit of Korea University Guro Hospital, Seoul, Korea from March 2012 to February 2014 were retrospectively included. Patients were divided into tremor-dominant-type and akinetic-rigid-type PD subgroups using part III of the Unified Parkinson's Disease Rating Scale. Olfaction was assessed by the Cross Cultural Smell Identification Test. RBD was screened using screening questionnaires. Initial cognitive function was assessed with Mini-Mental State Examination.
  
  
  RESULTS
  The PD-normosmia group had higher MMSE scores (p=0.008). PD patients who have both RBD and olfactory dysfunction had lower MMSE scores (p=0.013). Presence of both RBD and hyposmia in PD patients was more strongly correlated with poor cognitive dysfunction. PD patients with RBD and/or hyposmia primarily exhibited the akinetic-rigidity phenotype.
  
  
  CONCLUSIONS
  Olfactory dysfunction and RBD differed according to the motor phenotypes of PD. This suggests that olfactory dysfunction and RBD might relate to prognosis in patients with PD. Patients who have both hyposmia and RBD were more likely to exhibit cognitive dysfunction.
authors.affiliation: Department of Neurology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Republic of Korea.
authors.forename: Sung Hoon
authors.initials: SH
authors.lastname: Kang
authors.affiliation: Department of Neurology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Republic of Korea.
authors.forename: Hye Mi
authors.initials: HM
authors.lastname: Lee
authors.affiliation: Department of Neurology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Republic of Korea.
authors.forename: Woo-Keun
authors.initials: WK
authors.lastname: Seo
authors.affiliation: Department of Neurology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Republic of Korea.
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Neurology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Republic of Korea. Electronic address: parkinson@korea.ac.kr.
authors.forename: Seong-Beom
authors.initials: SB
authors.lastname: Koh
mesh_terms: D000368:Aged; D003072:Cognition Disorders / Q000150:complications*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009483:Neuropsychological Tests; D000857:Olfaction Disorders / Q000150:complications*; D010300:Parkinson Disease / Q000150:complications*; D017286:Polysomnography; D020187:REM Sleep Behavior Disorder / Q000150:complications*; D012189:Retrospective Studies; D011795:Surveys and Questionnaires
keywords: Cognitive dysfunction; Hyposmia; Motor phenotype; Parkinson's disease; REM sleep behavior disorder