title: Stability of mild cognitive impairment in newly diagnosed Parkinson's disease.
abstract: Mild cognitive impairment (MCI) is common in early Parkinson's disease (PD). We evaluated the stability of PD-MCI over time to determine its clinical utility as a marker of disease.
  
  
  
  212 newly diagnosed participants with PD were recruited into a longitudinal study and reassessed after 18 and 36 months. Participants completed a range of clinical and neuropsychological assessments. PD-MCI was classified using Movement Disorders Society Task Force level I (Montreal Cognitive Assessment <26) and level II (using cut-offs of 1, 1.5 and 2SD) criteria.
  
  
  
  After 36 months, 75% of participants returned; 8% of patients had developed a dementia all of which were previously PD-MCI. Applying level I criteria, 70% were cognitively stable, 19% cognitively declined and 11% improved over 36 months. Applying level II criteria (1, 1.5 and 2SD), 25% were cognitively stable, 41% cognitively declined, 15% improved and 19% fluctuated over 36 months. 18% of participants reverted to normal cognition from PD-MCI.
  
  
  
  Cognitive impairment in PD is complex, with some individuals' function fluctuating over time and some reverting to normal cognition. PD-MCI level I criteria may have greater clinical convenience, but more comprehensive level II criteria with 2SD cut-offs may offer greater diagnostic certainty.
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Lawson
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Yarnall
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.|Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Gordon W
authors.initials: GW
authors.lastname: Duncan
authors.affiliation: John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, UK.
authors.forename: David P
authors.initials: DP
authors.lastname: Breen
authors.affiliation: School of Medicine & Menzies Health Institute Queensland, Griffith University, Southport, Queensland, Australia.|School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia.
authors.forename: Tien K
authors.initials: TK
authors.lastname: Khoo
authors.affiliation: John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, UK.
authors.forename: Caroline H
authors.initials: CH
authors.lastname: Williams-Gray
authors.affiliation: John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, UK.
authors.forename: Roger A
authors.initials: RA
authors.lastname: Barker
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Burn
mesh_terms: D000368:Aged; D060825:Cognitive Dysfunction / Q000175:diagnosis*; D015331:Cohort Studies; D003704:Dementia / Q000175:diagnosis; D018450:Disease Progression; D004739:England; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000175:diagnosis*
keywords: COGNITION; DEMENTIA; PARKINSON'S DISEASE