title: β-amyloid dynamics in human plasma.
abstract: OBJECTIVE
  To investigate dynamic changes in human plasma β-amyloid (Aβ) concentrations, evaluate the effects of aging and amyloidosis on these dynamics, and determine their correlation with cerebrospinal fluid (CSF) Aβ concentrations.
  
  
  METHODS
  A repeated plasma and CSF sampling study.
  
  
  METHODS
  The Washington University School of Medicine in St Louis, Missouri.
  
  
  METHODS
  Older adults with amyloid deposition (Amyloid+), age-matched controls without amyloid deposition (Amyloid-), and younger normal controls (YNCs) were enrolled for the study.
  
  
  METHODS
  Hourly measurements of plasma Aβ were compared between groups by age and amyloidosis. Plasma Aβ and CSF Aβ concentrations were compared for correlation, linear increase, and circadian patterns.
  
  
  RESULTS
  Circadian patterns were observed in plasma Aβ, with diminished amplitudes with aging. Linear increase of Aβ was only observed for CSF Aβ in the YNC and Amyloid- groups, but not in the Amyloid+ group. No linear increase was observed for plasma Aβ. No significant correlations were found between plasma and CSF Aβ concentrations.
  
  
  CONCLUSIONS
  Plasma Aβ, like CSF, demonstrates a circadian pattern that is reduced in amplitude with increasing age but is unaffected by amyloid deposition. However, we found no evidence that plasma and CSF Aβ concentrations were related on an hourly or individual basis.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Huang
authors.forename: Rachel
authors.initials: R
authors.lastname: Potter
authors.forename: Wendy
authors.initials: W
authors.lastname: Sigurdson
authors.forename: Tom
authors.initials: T
authors.lastname: Kasten
authors.forename: Rose
authors.initials: R
authors.lastname: Connors
authors.forename: John C
authors.initials: JC
authors.lastname: Morris
authors.forename: Tammie
authors.initials: T
authors.lastname: Benzinger
authors.forename: Mark
authors.initials: M
authors.lastname: Mintun
authors.forename: Tim
authors.initials: T
authors.lastname: Ashwood
authors.forename: Mats
authors.initials: M
authors.lastname: Ferm
authors.forename: Samantha L
authors.initials: SL
authors.lastname: Budd
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Bateman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood / Q000134:cerebrospinal fluid*; D016229:Amyloid beta-Peptides / Q000097:blood* / Q000134:cerebrospinal fluid; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D010446:Peptide Fragments / Q000097:blood* / Q000134:cerebrospinal fluid; D013223:Statistics as Topic; D055815:Young Adult
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)