title: Incidence of mild cognitive impairment in the Pittsburgh Cardiovascular Health Study-Cognition Study.
abstract: OBJECTIVE
  The purpose of this study was to examine the incidence of mild cognitive impairment (MCI) and patterns of progression from incident MCI to dementia in 285 cognitively normal subjects (mean age, 78.9 years) in the Cardiovascular Health Study-Cognition Study from 1998-1999 to 2010-2011.
  
  
  RESULTS
  Two hundred (70%) of the participants progressed to MCI; the age-adjusted incidence of MCI was 111.09 (95% confidence interval, 88.13-142.95) per 1,000 person-years. A total of 107 (53.5%) of the incident MCI subjects progressed to dementia. The mean time from MCI to dementia was 2.8 ± 1.8 years. Forty (20%) of the incident MCI cases had an "unstable" course: 19 (9.5%) converted to MCI and later returned to normal; 10 (5%) converted to MCI, to normal, and later back to MCI; 7 (3.5%) converted to MCI, to normal, to MCI, and later to dementia; and 4 (2%) converted to MCI, to normal, and later to dementia. There was an increased mortality rate among the cognitively normal group (110.10 per 1,000 person-years) compared to those with incident MCI who converted to dementia (41.32 per 1,000 person-years).
  
  
  CONCLUSIONS
  The majority of the subjects aged >80 years developed an MCI syndrome, and half of them progressed to dementia. Once the MCI syndrome was present, the symptoms of dementia appeared within 2 to 3 years. Progression from normal to MCI or from normal to MCI to dementia is not always linear; subjects who developed MCI and later returned to normal can subsequently progress to dementia. Competing mortality and morbidity influence the study of incident MCI and dementia in population cohorts.
authors.affiliation: Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA. lopezol@upmc.edu
authors.forename: Oscar L
authors.initials: OL
authors.lastname: Lopez
authors.forename: James T
authors.initials: JT
authors.lastname: Becker
authors.forename: Yue-Fang
authors.initials: YF
authors.lastname: Chang
authors.forename: Robert A
authors.initials: RA
authors.lastname: Sweet
authors.forename: Steven T
authors.initials: ST
authors.lastname: DeKosky
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gach
authors.forename: Owen T
authors.initials: OT
authors.lastname: Carmichael
authors.forename: Eric
authors.initials: E
authors.lastname: McDade
authors.forename: Lewis H
authors.initials: LH
authors.lastname: Kuller
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D060825:Cognitive Dysfunction / Q000453:epidemiology*; D003704:Dementia / Q000453:epidemiology*; D018450:Disease Progression; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008297:Male; D012307:Risk Factors; D012720:Severity of Illness Index