title: Distinct cognitive phenotypes in Alzheimer's disease in older people.
abstract: BACKGROUND
  Alzheimer's disease (AD) is considered to be a disorder predominantly affecting memory. It is increasingly recognized that the cognitive profile may be heterogeneous. We hypothesized that it would be possible to define distinct “cognitive phenotypes” in older people with AD.
  
  
  METHODS
  Participants from three individual studies were included, consisting of 109 patients with a diagnosis of probable AD, and 91 age- and gender-matched control participants. All had demographic and cognitive assessment data available, including the Cambridge Cognitive Examination of the Elderly (CAMCOG). The CAMCOG scores and sub-scores were further analyzed using hierarchical cluster analysis and factor analysis.
  
  
  RESULTS
  Three clusters were identified. The scores loaded onto three factors representing the domains of attention, praxis, calculation, and perception; memory; and language comprehension and executive function. The main difference between the clusters related to degree of memory impairment. The composite score for memory between the clusters remained significantly different despite adjustment for illness duration and age of onset (p < 0.001).
  
  
  CONCLUSIONS
  These data suggest clinical heterogeneity within an older group of people with AD. This may have implications for diagnosis, prognosis, response to currently available treatments, and the development of novel therapies.
authors.affiliation: Department of Older Peoples Medicine, Freeman Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, High Heaton, Newcastle upon Tyne, UK. emma.vardy@ncl.ac.uk
authors.forename: Emma R L C
authors.initials: ER
authors.lastname: Vardy
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Ford
authors.forename: Peter
authors.initials: P
authors.lastname: Gallagher
authors.forename: Rosie
authors.initials: R
authors.lastname: Watson
authors.forename: Ian G
authors.initials: IG
authors.lastname: McKeith
authors.forename: Andrew
authors.initials: A
authors.lastname: Blamire
authors.forename: John T
authors.initials: JT
authors.lastname: O'Brien
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000145:classification / Q000523:psychology*; D001288:Attention; D016022:Case-Control Studies; D003071:Cognition; D032882:Comprehension; D056344:Executive Function; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory; D009483:Neuropsychological Tests; D010465:Perception; D010641:Phenotype