title: Aβ amyloid, cognition, and APOE genotype in healthy older adults.
abstract: BACKGROUND
  Only one study has investigated the relationship between cerebral β-amyloid (Aβ), apolipoprotein E (APOE) ε4 genotype, and cognition. Although significant relationships between cerebral Aβ and cognition were observed in ε4 carriers but not noncarriers, the magnitude of this relationship was not reported. Further, when demographic variables were controlled, the influence of APOE ε4 on the relationship between cerebral Aβ and cognition dissipated.
  
  
  METHODS
  In 144 healthy older adults who had undergone amyloid scanning and APOE ε4 genotyping in the Australian Imaging, Biomarkers, and Lifestyle (AIBL) Flagship Study of Ageing, correlations were conducted to determine the magnitude of relationship between cerebral Aβ and cognition in ε4 carriers and noncarriers. Fisher's Z was used to compare these correlations and Cohen's q determined the magnitude of difference between correlations.
  
  
  RESULTS
  Cerebral Aβ was significantly associated with tasks of visual and verbal episodic memory in APOE ε4 carriers. This association was not observed in ε4 noncarriers. The relationship between cerebral Aβ and episodic memory in ε4 carriers was significantly different from that in ε4 noncarriers, and the magnitude of this difference was small to moderate.
  
  
  CONCLUSIONS
  In APOE ε 4 carriers, there is a moderate negative relationship between cerebral Aβ and episodic memory. This suggests that increased cerebral Aβ may signify the onset of preclinical AD, especially in healthy older adults who are genetically at risk for AD.
authors.affiliation: Department of Psychiatry, University of Melbourne, Parkville, Australia. y.lim@mhri.edu.au
authors.forename: Yen Ying
authors.initials: YY
authors.lastname: Lim
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Ellis
authors.forename: David
authors.initials: D
authors.lastname: Ames
authors.forename: David
authors.initials: D
authors.lastname: Darby
authors.forename: Karra
authors.initials: K
authors.lastname: Harrington
authors.forename: Ralph N
authors.initials: RN
authors.lastname: Martins
authors.forename: Colin L
authors.initials: CL
authors.lastname: Masters
authors.forename: Christopher
authors.initials: C
authors.lastname: Rowe
authors.forename: Greg
authors.initials: G
authors.lastname: Savage
authors.forename: Cassandra
authors.initials: C
authors.lastname: Szoeke
authors.forename: Victor L
authors.initials: VL
authors.lastname: Villemagne
authors.forename: Paul
authors.initials: P
authors.lastname: Maruff
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000235:genetics; D016229:Amyloid beta-Peptides / Q000032:analysis / Q000378:metabolism*; D053327:Apolipoprotein E4 / Q000235:genetics*; D001315:Australia; D001921:Brain / Q000378:metabolism*; D003071:Cognition / Q000502:physiology*; D005260:Female; D005838:Genotype; D006579:Heterozygote; D006801:Humans; D008297:Male; D061212:Memory, Episodic; D009483:Neuropsychological Tests
chemical_list: D016229:Amyloid beta-Peptides; D053327:Apolipoprotein E4