title: Correlation of sleep disturbance and cognitive impairment in patients with Parkinson's disease.
abstract: OBJECTIVE
  Cognitive impairment is a common nonmotor symptom of Parkinson's disease (PD) and is associated with high mortality, caregiver distress, and nursing home placement. The risk factors for cognitive decline in PD patients include advanced age, longer disease duration, rapid eye movement sleep behavior disorder, hallucinations, excessive daytime sleepiness, and nontremor symptoms including bradykinesia, rigidity, postural instability, and gait disturbance. We conducted a cross-sectional study to determine which types of sleep disturbances are related to cognitive function in PD patients.
  
  
  METHODS
  A total of 71 PD patients (29 males, mean age 66.46 ± 8.87 years) were recruited. All patients underwent the Mini- Mental State Examination (MMSE) and the Korean Version of the Montreal Cognitive Assessments (MoCA-K) to assess global cognitive function. Sleep disorders were evaluated with the Stanford Sleepiness Scale, Epworth Sleepiness Scale, Insomnia Severity Index (ISI), Pittsburg Sleep Quality Index, and Parkinson's Disease Sleep Scale in Korea (PDSS).
  
  
  RESULTS
  The ISI was correlated with the MMSE, and total PDSS scores were correlated with the MMSE and the MoCA-K. In each item of the PDSS, nocturnal restlessness, vivid dreams, hallucinations, and nocturnal motor symptoms were positively correlated with the MMSE, and nocturnal restlessness and vivid dreams were significantly related to the MoCA-K. Vivid dreams and nocturnal restlessness are considered the most powerful correlation factors with global cognitive function, because they commonly had significant correlation to cognition assessed with both the MMSE and the MoCA-K.
  
  
  CONCLUSIONS
  We found a correlation between global cognitive function and sleep disturbances, including vivid dreams and nocturnal restlessness, in PD patients.
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Eun Ja
authors.initials: EJ
authors.lastname: Kim
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Joon Hyun
authors.initials: JH
authors.lastname: Baek
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Dong Jin
authors.initials: DJ
authors.lastname: Shin
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Hyeon-Mi
authors.initials: HM
authors.lastname: Park
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Yeong-Bae
authors.initials: YB
authors.lastname: Lee
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Kee-Hyung
authors.initials: KH
authors.lastname: Park
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Shin
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Young
authors.initials: Y
authors.lastname: Noh
authors.affiliation: Department of Neurology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Young Hee
authors.initials: YH
authors.lastname: Sung
keywords: Cognitive impairment; Parkinson’s disease; Sleep disturbance