title: Natural course of mild cognitive impairment in Parkinson disease: A 5-year population-based study.
abstract: OBJECTIVE
  To examine the incidence, progression, and reversion of mild cognitive impairment in patients with Parkinson disease (PD-MCI) over 5 years.
  
  
  METHODS
  A population-based cohort of patients with incident PD underwent repeated neuropsychological testing of attention, executive function, memory, and visuospatial abilities at baseline (n = 178), 1 year (n = 175), 3 years (n = 163), and 5 years (n = 150). Patients were classified as PD-MCI and diagnosed with dementia according to published criteria.
  
  
  RESULTS
  Thirty-six patients (20.2%) fulfilled criteria for PD-MCI at baseline. Among those with normal cognition at baseline (n = 142), the cumulative incidence of PD-MCI was 9.9% after 1 year, 23.2% after 3 years, and 28.9% after 5 years of follow-up. Overall, 39.1% of patients with baseline or incident PD-MCI progressed to dementia during the 5-year study period. The conversion rate to dementia was 59.1% in patients with persistent PD-MCI at 1 year vs 7.2% in those with normal cognition during the first year (adjusted odds ratio 16.6, 95% confidence interval 5.1-54.7,p< 0.001). A total of 27.8% of patients with baseline PD-MCI and 24.2% of those with incident PD-MCI had reverted to normal cognition at study end, but the reversion rate decreased to 9.4% in those with persistent PD-MCI at 2 consecutive visits. Compared with cognitively normal patients, PD-MCI reverters within the first 3 years of follow-up were at increased risk of subsequently developing dementia (adjusted odds ratio 10.7, 95% confidence interval 1.5-78.5,p= 0.019).
  
  
  CONCLUSIONS
  Early PD-MCI, regardless of persistence or reversion to normal cognition, has prognostic value for predicting dementia in patients with PD.
authors.affiliation: From the Norwegian Centre for Movement Disorders (K.F.P., G.A.); Department of Neurology (K.F.P., G.A.) and Memory Clinic (K.F.P., G.A.), Stavanger University Hospital; Network for Medical Sciences (J.P.L.), University of Stavanger; and Department of Neurology (O.-B.T.), Haukeland University Hospital, Bergen, Norway. pekf@sus.no.
authors.forename: Kenn Freddy
authors.initials: KF
authors.lastname: Pedersen
authors.affiliation: From the Norwegian Centre for Movement Disorders (K.F.P., G.A.); Department of Neurology (K.F.P., G.A.) and Memory Clinic (K.F.P., G.A.), Stavanger University Hospital; Network for Medical Sciences (J.P.L.), University of Stavanger; and Department of Neurology (O.-B.T.), Haukeland University Hospital, Bergen, Norway.
authors.forename: Jan Petter
authors.initials: JP
authors.lastname: Larsen
authors.affiliation: From the Norwegian Centre for Movement Disorders (K.F.P., G.A.); Department of Neurology (K.F.P., G.A.) and Memory Clinic (K.F.P., G.A.), Stavanger University Hospital; Network for Medical Sciences (J.P.L.), University of Stavanger; and Department of Neurology (O.-B.T.), Haukeland University Hospital, Bergen, Norway.
authors.forename: Ole-Bjørn
authors.initials: OB
authors.lastname: Tysnes
authors.affiliation: From the Norwegian Centre for Movement Disorders (K.F.P., G.A.); Department of Neurology (K.F.P., G.A.) and Memory Clinic (K.F.P., G.A.), Stavanger University Hospital; Network for Medical Sciences (J.P.L.), University of Stavanger; and Department of Neurology (O.-B.T.), Haukeland University Hospital, Bergen, Norway.
authors.forename: Guido
authors.initials: G
authors.lastname: Alves
mesh_terms: D000368:Aged; D060825:Cognitive Dysfunction / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology; D003704:Dementia / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008609:Mental Status Schedule; D008875:Middle Aged; D009483:Neuropsychological Tests; D009664:Norway; D016017:Odds Ratio; D010300:Parkinson Disease / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D011379:Prognosis; D011446:Prospective Studies; D012306:Risk