title: Dementia in Parkinson's disease: a 20-year neuropsychological study (Sydney Multicentre Study).
abstract: OBJECTIVE
  To determine whether neuropsychological measures differ between patients with idiopathic Parkinson's disease (PD) who acquire dementia within 10 years of disease onset versus those who acquire dementia later in the disease course, using data from the longitudinal Sydney Multicentre Study of PD.
  
  
  METHODS
  The Sydney Multicentre Study of PD is a cohort of 149 community-living de novo patients with idiopathic PD studied over a 20-year period. Detailed clinical and neuropsychological tests were administered at baseline and at 3, 5, 10, 15 and 20 years, and the dementia status was assessed at each time point. For the present study, the pattern of longitudinal neuropsychological measures was compared between PD patients with the onset of dementia in the middle (5-10 years, mid-stage PD dementia, N = 20) or late (>10 years, late-stage PD dementia, N = 10) disease stages using analysis of variance and multiple linear regression modelling, and the relationship between age and dementia onset assessed using survival statistics.
  
  
  RESULTS
  Mid-stage PD dementia patients were differentiated from late-stage PD dementia patients by having greater deficits in vocabulary skills prior to and at dementia onset. The pattern of cognitive deficits following dementia onset are similar, and there is no difference in the age of dementia onset between the different PD groups.
  
  
  CONCLUSIONS
  These data suggest that the evolution of dementia within PD occurs at around 70 years of age, regardless of the time of PD onset, and affects cognitive domains in a similar way, although patients with earlier-onset PD have a preserved linguistic ability prior to dementia onset.
authors.affiliation: Neuroscience Research Australia and the University of New South Wales, Sydney, Australia.
authors.forename: W G J
authors.initials: WG
authors.lastname: Reid
authors.forename: M A
authors.initials: MA
authors.lastname: Hely
authors.forename: J G L
authors.initials: JG
authors.lastname: Morris
authors.forename: C
authors.initials: C
authors.lastname: Loy
authors.forename: G M
authors.initials: GM
authors.lastname: Halliday
mesh_terms: D000367:Age Factors; D017668:Age of Onset; D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use; D001971:Bromocriptine / Q000627:therapeutic use; D003071:Cognition / Q000502:physiology; D015331:Cohort Studies; D003704:Dementia / Q000209:etiology* / Q000523:psychology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use; D008137:Longitudinal Studies; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D009460:Neurologic Examination; D009483:Neuropsychological Tests; D009517:New South Wales; D010300:Parkinson Disease / Q000150:complications* / Q000523:psychology*; D016019:Survival Analysis
chemical_list: D000978:Antiparkinson Agents; D001971:Bromocriptine; D007980:Levodopa