title: Reduced Rapid Eye Movement Density in Parkinson Disease: A Polysomnography-Based Case-Control Study.
abstract: To explore rapid eye movement density (RD) in patients with idiopathic Parkinson disease (IPD) and to investigate its usefulness as surrogate marker of excessive daytime sleepiness, a frequent complaint in IPD patients.
  
  
  
  Retrospective polysomnography study on 81 subjects without dementia: 29 patients with early stage IPD (disease duration ≤ 3 y), 21 patients with middle- stage IPD (disease duration > 3 and < 8 y) and 31 healthy controls (HC). Rapid eye movement (REM) sleep was defined as any REM episode with > 3 min of continuous REM sleep. RD was defined as number of ocular movements per minute of REM sleep. Patients with early stage IPD and HC fulfilled the PD-specific sleepiness questionnaires Parkinson's Disease Sleep Scale (PDSS) and the Nonmotor Symptoms Questionnaire for Parkinson's disease (NMSQuest).
  
  
  
  RD was lower in patients with IPD than in HC. The difference was most significant between patients with middle stage IPD and HC (P = 0.001), and most prominent for the third REM episode, again when comparing patients with middle stage IPD and HC (P = 0.03). RD was independent from sex, age, and other sleep parameters. In early stage IPD, RD correlated with the PDSS score (r = -0.63, P = 0.001) and the sleep-related questions of the NMSQuest score (r = 0.48, P = 0.017).
  
  
  
  REM density is reduced in patients with IPD and correlates with subjective scores on sleep impairment. As an indicator of persistent high sleep pressure, reduced RD in IPD is eligible as a biomarker of excessive daytime sleepiness in IPD. It possibly reflects direct involvement of the brainstem REM generation sites by the disease process. RD is a promising new tool for sleep research in IPD.
authors.affiliation: Department of Neurosurgery, Centre Hospitalier de Luxembourg, Luxembourg-City, Luxembourg.
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Schroeder
authors.affiliation: Interdisciplinary Sleep Laboratory, Centre Hospitalier de Luxembourg.
authors.forename: Olivier
authors.initials: O
authors.lastname: Rufra
authors.affiliation: Competence Center of Methodology and Statistics, Luxembourg Institute of Health, Luxembourg-City, Luxembourg.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sauvageot
authors.affiliation: Competence Center of Methodology and Statistics, Luxembourg Institute of Health, Luxembourg-City, Luxembourg.
authors.forename: François
authors.initials: F
authors.lastname: Fays
authors.affiliation: Department of Neurosciences, Centre Hospitalier de Luxembourg.
authors.forename: Vannina
authors.initials: V
authors.lastname: Pieri
authors.affiliation: Department of Neurosciences, Centre Hospitalier de Luxembourg.
authors.forename: Nico J
authors.initials: NJ
authors.lastname: Diederich
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000503:physiopathology*; D017286:Polysomnography; D012189:Retrospective Studies; D012895:Sleep, REM / Q000502:physiology*
keywords: Parkinson disease; REM density; REM sleep; excessive daytime sleepiness