title: A three-factor model of cognition in Alzheimer disease.
abstract: OBJECTIVE
  To use principal factors analysis to model cognition in Alzheimer disease.
  
  
  BACKGROUND
  Earlier studies have used factor analysis to examine the effects on Alzheimer disease cognition of either heterogeneity in premorbid cognition or heterogeneity in the disease process itself. In the current study, both sources of heterogeneity were incorporated within a single model.
  
  
  METHODS
  Two hundred sixty-one patients with probable Alzheimer disease (92 White Non-Hispanic, 148 Hispanic, and 21 African-American) were tested with the Mini-Mental Status Examination, the Assessment of Cognitive Abilities in Dementia, and the Short Portable Mental Status Examination.
  
  
  RESULTS
  Three factors were obtained: one with loadings for memory and orientation, a second with loadings for language and praxis, and a third with loadings for executive functions. Factors 1 and 2 declined over 1.82 years (p = 0.0002, p = 0.0001); Factor 3 scores remained invariant over this period (p = 0.16). Furthermore, only Factor 3 scores correlated with either education (p = 0.0001) or ethnicity (p = 0.0001).
  
  
  CONCLUSIONS
  A possible interpretation is that Factors 1 and 2 may reflect two components of the Alzheimer disease process while Factor 3 may provide an estimate of premorbid cognition. A potential practical application of the analysis is that it may provide a measure of Alzheimer disease decline that is free from correlation with education or ethnicity.
authors.affiliation: Departments of Psychiatry and Neurology, University of Miami School of Medicine, Miami, Florida 33136, USA. ssevsh@med.Miami.edu
authors.forename: Steven
authors.initials: S
authors.lastname: Sevush
authors.forename: Gloria
authors.initials: G
authors.lastname: Peruyera
authors.forename: Annette
authors.initials: A
authors.lastname: Bertran
authors.forename: Wendy
authors.initials: W
authors.lastname: Cisneros
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000523:psychology*; D003071:Cognition; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008960:Models, Psychological; D009483:Neuropsychological Tests; D011379:Prognosis; D011569:Psychiatric Status Rating Scales; D013647:Task Performance and Analysis