title: Dissociations among daytime sleepiness, nighttime sleep, and cognitive status in Parkinson's disease.
abstract: BACKGROUND
  Daytime and nighttime sleep disturbances and cognitive impairment occur frequently in Parkinson's disease (PD), but little is known about the interdependence of these non-motor complications. Thus, we examined the relationships among excessive daytime sleepiness, nighttime sleep quality and cognitive impairment in PD, including severity and specific cognitive deficits.
  
  
  METHODS
  Ninety-three PD patients underwent clinical and neuropsychological evaluations including the Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI). Patients were classified as having normal cognition (PD-NC), mild cognitive impairment (PD-MCI), or dementia (PDD) using recently proposed Movement Disorder Society PD-MCI and PDD criteria. Relationships between the sleep and cognitive measures and PD cognitive groups were examined.
  
  
  RESULTS
  The PD cohort included PD-NC (n = 28), PD-MCI (n = 40), and PDD (n = 25) patients. ESS scores, as a measure of daytime sleepiness, were significantly worse (p = 0.005) in cognitively impaired PD patients, particularly PDD patients. ESS scores correlated significantly with Mini-Mental State Examination scores and also with cognitive domain scores for attention/working memory, executive function, memory, and visuospatial function. In contrast, PSQI scores, as a measure of nighttime sleep quality, neither differed among cognitive groups nor correlated with any cognitive measures.
  
  
  CONCLUSIONS
  Daytime sleepiness in PD, but not nighttime sleep problems, is associated with cognitive impairment in PD, especially in the setting of dementia, and attention/working memory, executive function, memory, and visuospatial deficits. The presence of nighttime sleep problems is pervasive across the PD cognitive spectrum, from normal cognition to dementia, and is not independently associated with cognitive impairment or deficits in cognitive domains.
authors.affiliation: Department of Neurological Sciences, Rush University Medical Center, Chicago, IL 60612, USA. Jennifer_G_Goldman@rush.edu
authors.forename: Jennifer G
authors.initials: JG
authors.lastname: Goldman
authors.forename: Reena A
authors.initials: RA
authors.lastname: Ghode
authors.forename: Bichun
authors.initials: B
authors.lastname: Ouyang
authors.forename: Bryan
authors.initials: B
authors.lastname: Bernard
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Goetz
authors.forename: Glenn T
authors.initials: GT
authors.lastname: Stebbins
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001288:Attention / Q000502:physiology; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D056344:Executive Function / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D012893:Sleep Wake Disorders / Q000209:etiology / Q000503:physiopathology*
keywords: Dementia; Excessive daytime sleepiness; Executive function; MCI (mild cognitive impairment); Parkinson's disease; Sleep disorders