title: Mild cognitive impairment in a community sample: the Sydney Memory and Ageing Study.
abstract: BACKGROUND
  Mild cognitive impairment (MCI) is associated with an increased dementia risk. This study reports incidence of MCI subtypes, rates of progression to dementia, and stability of MCI classification.
  
  
  METHODS
  We examined 873 community-dwelling adults aged 70 to 90 years over 2 years as part of an ongoing population-based longitudinal study, the Sydney Memory and Ageing Study. Neuropsychological testing assessed five cognitive domains, and a diagnosis of no cognitive impairment, MCI, or dementia (follow-up only) was made according to published criteria.
  
  
  RESULTS
  The incidence of MCI was 104.6 (95% confidence interval: 81.6-127.7) per 1000 person-years, with higher incidence in men (men, 156.8; women, 70.3). Incidence rates for single-domain amnestic, multiple-domain amnestic, single-domain nonamnestic, and multiple-domain nonamnestic MCI were 47.7, 7.9, 45.0, and 3.9 per 1000 person-years, respectively. The 2-year rate of progression from MCI at baseline to dementia was 4.8%, being highest for multidomain amnestic MCI (9.1%). Of those with MCI at baseline, 28.2% reverted to no cognitive impairment at follow-up. Sensitivity analyses by redefining criteria for cognitive impairment did not affect stability of diagnosis, although changing the threshold of domain impairment reduced baseline MCI prevalence from 36.7% to 5.7% and incidence to 23.5, and increased 2-year progression rate from MCI to dementia to 14.3%.
  
  
  CONCLUSIONS
  Incidence rates for MCI are higher than previously reported, particularly in men and for single-domain MCI; rates for amnestic and nonamnestic MCI were comparable. Multidomain amnestic MCI was the most likely subtype to progress to dementia, but overall, the diagnosis of MCI, particularly single-domain MCI, shows considerable instability.
authors.affiliation: Primary Dementia Collaborative Research Centre, School of Psychiatry, University of New South Wales, New South Wales, Australia. h.brodaty@unsw.edu.au
authors.forename: Henry
authors.initials: H
authors.lastname: Brodaty
authors.forename: Megan
authors.initials: M
authors.lastname: Heffernan
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Kochan
authors.forename: Brian
authors.initials: B
authors.lastname: Draper
authors.forename: Julian N
authors.initials: JN
authors.lastname: Trollor
authors.forename: Simone
authors.initials: S
authors.lastname: Reppermund
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Slavin
authors.forename: Perminder S
authors.initials: PS
authors.lastname: Sachdev
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D060825:Cognitive Dysfunction / Q000145:classification / Q000453:epidemiology* / Q000503:physiopathology*; D003704:Dementia / Q000145:classification / Q000453:epidemiology* / Q000503:physiopathology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008568:Memory / Q000502:physiology; D009517:New South Wales / Q000453:epidemiology; D015995:Prevalence; D012111:Residence Characteristics; D012307:Risk Factors; D017678:Sex Distribution