title: Sleep correlates of trait executive function and memory in Parkinson's disease.
abstract: BACKGROUND
  Sleep disturbance and cognitive impairment are correlated in non-diseased populations, but their association in Parkinson's disease (PD) is uncertain. Prior studies examining measures of cognition in relation to sleep have used either self-report or actigraphically measured sleep and have produced conflicting findings.
  
  
  OBJECTIVE
  In this descriptive study, we correlated measurements of sleep in PD patients derived from the gold-standard measurement, in-lab polysomnography, with an extensive battery of cognitive measures. We hypothesized that poorer sleep would be related to relatively more impaired cognition.
  
  
  METHODS
  Idiopathic PD patients (n = 34) completed a cognitive battery encompassing three broad domains (executive function, immediate memory and delayed memory), and underwent PSG for two nights. Scores for each domain from individual cognitive measures were converted to z-scores and then averaged to produce a composite score. We used second night PSG data and quantified measures of sleep architecture, sleep continuity, sleep apnea and nocturnal movement (periodic leg movements, PLMS).
  
  
  RESULTS
  Lower executive function was associated with higher PLMS after controlling for chronological age, mini-mental state examination scores, and UPDRS motor subscale scores. These results were independent from psychomotor speed. There was a marginally significant positive correlation between the proportion of time spent in REM and immediate recall ability. Measures of sleep continuity and sleep apnea were unrelated to cognition in these patients.
  
  
  CONCLUSIONS
  PLMS, known to be a frequent feature of PSG-measured sleep in PD, may be an important correlate of impaired executive function in PD. Whether treating this disorder of sleep results in improvement in cognition remains to be determined.
authors.affiliation: Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, USA Department of Psychology and Neuroscience, Baylor University, Waco, TX, USA.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Scullin
authors.affiliation: Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Jacqueline A
authors.initials: JA
authors.lastname: Fairley
authors.affiliation: Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Lynn Marie
authors.initials: LM
authors.lastname: Trotti
authors.affiliation: Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Felicia C
authors.initials: FC
authors.lastname: Goldstein
authors.affiliation: Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Stewart A
authors.initials: SA
authors.lastname: Factor
authors.affiliation: Department of Neurology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Donald L
authors.initials: DL
authors.lastname: Bliwise
mesh_terms: D000368:Aged; D003072:Cognition Disorders / Q000209:etiology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications*; D012720:Severity of Illness Index; D012893:Sleep Wake Disorders / Q000209:etiology*; D013223:Statistics as Topic
keywords: Sleep related periodic leg movements; aging; cognition; neurodegenerative diseases; sleep disorders; sleep fragmentation