title: Plasma beta amyloid level and depression in older adults.
abstract: BACKGROUND
  Older adults with depression have an increased risk of developing dementia. Low plasma beta-amyloid 42 (Aβ42) and Aβ42/Aβ40 have emerged as promising biomarkers of dementia. The association between depression and plasma Aβ is unclear.
  
  
  METHODS
  In this longitudinal study of 988 community-dwelling elders from the Health Aging and Body Composition study, depression was assessed with the Center for Epidemiologic Studies-Depression Scale 10-item version. We determined the association between Aβ42 and Aβ42/Aβ40 tertile and depression at baseline and over 9 years. We also stratified the models to determine if apolipoprotein E e4 allele status modified the associations.
  
  
  RESULTS
  Mean baseline age was 74.0 ± 3.0 years, 51 (5.2%) participants had depression, 545 (55.2%) were women, 531 (53.7%) were black, and 286 (30.7%) had one or more apolipoprotein E e4 allele. At baseline, there was no association between Aβ42/Aβ40 or Aβ42 and depression. Over 9 years, 220 (23.5%) participants developed depression. In adjusted Cox proportional hazards models, among those with one or more e4 allele, low Aβ42/Aβ40 was associated with an increased risk of developing depression over time (low 10.8% vs high 3.2%, hazard ratio = 2.38, 95% confidence interval: 1.15-4.92). Among those with no e4 allele, there was no association between Aβ42/Aβ40 and risk of depression over time (13.3% vs 17.5%, hazard ratio = 0.80, 95% confidence interval: 0.52-1.23; p value for interaction = .003).
  
  
  CONCLUSIONS
  The association between low plasma Aβ42/Aβ40 and increased risk of incident depression among those with one or more apolipoprotein E e4 allele implies a synergistic relationship similar to that found with dementia. Future work should investigate the interrelationships among plasma Aβ42/Aβ40, depression, and dementia.
authors.affiliation: Center for Aging and Population Health, Department of Epidemiology, University of Pittsburgh, Pittsburgh, PA 15213, USA. alw111@pitt.edu
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Metti
authors.forename: Jane A
authors.initials: JA
authors.lastname: Cauley
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.forename: Hilsa N
authors.initials: HN
authors.lastname: Ayonayon
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Barry
authors.forename: Lewis M
authors.initials: LM
authors.lastname: Kuller
authors.forename: Suzanne
authors.initials: S
authors.lastname: Satterfield
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Simonsick
authors.forename: Kristine
authors.initials: K
authors.lastname: Yaffe
mesh_terms: D000368:Aged; D000375:Aging / Q000097:blood* / Q000235:genetics / Q000523:psychology*; D016229:Amyloid beta-Peptides / Q000097:blood*; D053327:Apolipoprotein E4 / Q000235:genetics; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D003704:Dementia / Q000097:blood / Q000235:genetics; D003863:Depression / Q000097:blood* / Q000235:genetics; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010414:Pennsylvania; D010446:Peptide Fragments / Q000097:blood*; D011446:Prospective Studies; D012307:Risk Factors; D013714:Tennessee
chemical_list: D016229:Amyloid beta-Peptides; D053327:Apolipoprotein E4; D015415:Biomarkers; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)