Plasma beta amyloid and the risk of Alzheimer disease and dementia in elderly men: a prospective, population-based cohort study.
BACKGROUND
Beta amyloid (Abeta) protein accumulates in the brains of individuals with Alzheimer disease (AD) and is detectable in cerebrospinal fluid and plasma.


OBJECTIVE
To examine plasma levels of Abeta peptides Abeta(40) and Abeta(42) as predictors of incident AD and other types of dementia.


METHODS
Prospective, population-based cohort study.


METHODS
The Uppsala Longitudinal Study of Adult Men.


METHODS
Plasma Abeta(40) and Abeta(42) levels were analyzed as predictors of incident AD in 1045 men at age 70 years and 680 men at age 77 years using Cox proportional hazards analyses. Alzheimer disease and other types of dementia were diagnosed by standardized screening, clinical evaluation, and medical record review.


METHODS
Hazard ratios of AD (primary outcome) and vascular dementia or other dementia (secondary outcomes) according to baseline levels of plasma Abeta(40) and Abeta(42).


RESULTS
From the age of 77 years at baseline, 46 individuals developed AD at follow-up (median, 5.3 years). A low plasma Abeta(40) level at age 77 years was associated with higher incidence of AD. The multivariate-adjusted hazard ratio was 4.87 (95% confidence interval, 1.63-14.6) for the lowest Abeta(40) tertile compared with the highest tertile. On follow-up from age 70 years at baseline (median, 11.2 years), 82 individuals developed AD. Plasma Abeta(40) and Abeta(42) levels measured at age 70 years were not significantly associated with incident AD.


CONCLUSIONS
Low plasma Abeta(40) levels predicted incident AD in elderly men independently of potential confounders. Plasma Abeta(42) levels were not significantly associated with AD incidence. The clinical value of Abeta measurement in plasma remains to be established in future studies.
Sundelöf
Johan
J
Uppsala University, Department of Public Health and Geriatrics, Uppsala Science Park, Dag Hammarskölds väg 14B, Uppsala, Sweden.
Giedraitis
Vilmantas
V
Irizarry
Michael C
MC
Sundström
Johan
J
Ingelsson
Erik
E
Rönnemaa
Elina
E
Arnlöv
Johan
J
Gunnarsson
Malin Degerman
MD
Hyman
Bradley T
BT
Basun
Hans
H
Ingelsson
Martin
M
Lannfelt
Lars
L
Kilander
Lena
L
D000368:Aged; D000544:Alzheimer Disease / Q000097:blood* / Q000453:epidemiology*; D016229:Amyloid beta-Peptides / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D003704:Dementia / Q000097:blood / Q000453:epidemiology; D015140:Dementia, Vascular / Q000097:blood / Q000453:epidemiology; D018572:Disease-Free Survival; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology
D016229:Amyloid beta-Peptides; D015415:Biomarkers