title: Poor attentional function predicts cognitive decline in patients with non-demented Parkinson's disease independent of motor phenotype.
abstract: BACKGROUND
  Postural instability gait difficulty (PIGD) motor phenotype in Parkinson's disease (PD) is associated with a faster rate of cognitive decline than in tremor dominant cases and may be a risk factor for incident dementia. People with PD display attentional deficits; however, it is not clear whether attentional deficits in patients with non-demented PD are associated with (i) PIGD phenotype and/or (ii) subsequent cognitive decline.
  
  
  OBJECTIVE
  (i) To examine rates of cognitive decline (Mini-Mental State Examination (MMSE) and Cambridge Cognitive Examination (CAMCOG)) over 3 years in subjects with non-demented PD aged over 65 years, (ii) using Cognitive Drug Research computerised assessment test battery, determine the rate of change in power of attention (PoA) scores over time (sum of mean choice reaction time, simple reaction time and digit vigilance reaction time scores), (iii) determine whether the PIGD phenotype is associated with changes in PoA and (iv) establish whether baseline PoA is associated with subsequent cognitive decline.
  
  
  RESULTS
  14 subjects (38%) were classified as PIGD motor phenotype at baseline. Cognitive decline was greater in PIGD compared with non-PIGD subjects (p < or = 0.02). PIGD phenotype was not associated with baseline PoA score although it was associated with subsequent worsening in PoA (mean PoA increase/year: non-PIGD subjects 11.4 ms; PIGD subjects 244.0 ms; p = 0.01). Higher baseline PoA scores were associated with greater cognitive decline (MMSE, p = 0.03; CAMCOG, p = 0.05) independent of PIGD status.
  
  
  CONCLUSIONS
  PIGD phenotype and attention deficits are independently associated with a greater rate of cognitive decline in patients with non-demented PD. We propose that subtle attentional deficits in patients with non-demented PD predict subsequent cognitive impairment.
authors.affiliation: Institute for Ageing and Health, Wolfson Research Centre, Newcastle General Hospital, Westgate Road, Newcastle upon Tyne NE4 6BE, UK. john-paul.taylor@ncl.ac.uk
authors.forename: J-P
authors.initials: JP
authors.lastname: Taylor
authors.forename: E N
authors.initials: EN
authors.lastname: Rowan
authors.forename: D
authors.initials: D
authors.lastname: Lett
authors.forename: J T
authors.initials: JT
authors.lastname: O'Brien
authors.forename: I G
authors.initials: IG
authors.lastname: McKeith
authors.forename: D J
authors.initials: DJ
authors.lastname: Burn
mesh_terms: D000368:Aged; D001288:Attention; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis* / Q000473:pathology; D003704:Dementia / Q000150:complications* / Q000175:diagnosis; D018450:Disease Progression; D005260:Female; D020233:Gait Disorders, Neurologic / Q000150:complications / Q000175:diagnosis; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000175:diagnosis* / Q000473:pathology; D010641:Phenotype; D012044:Regression Analysis; D014202:Tremor / Q000150:complications / Q000175:diagnosis