APOE genotype and cognitive decline in a middle-aged cohort.
BACKGROUND
Most longitudinal studies of nondemented persons have reported greater cognitive decline among APOE epsilon4 carriers vs noncarriers. However, most studies involved elderly samples (aged 65+) and were not large enough to examine the three APOE alleles separately.


METHODS
Change in cognitive function was examined over a 6-year period using three neuropsychological tests among four APOE genotype groups (epsilon2/2 + epsilon2/3, epsilon3/3 (referent), epsilon4/2 + epsilon4/3, epsilon4/4). The population-based sample included 1,693 African Americans and 6,202 Caucasians initially ages 47 to 68.


RESULTS
There was increasingly greater cognitive decline from the epsilon2 group to the epsilon4/4 group in Caucasians for two of the three tests. The combination of APOE epsilon4 with hypercholesterolemia or diabetes showed the greatest cognitive decline. Among African Americans, only the test measuring psychomotor speed showed associations with APOE genotype.


CONCLUSIONS
APOE epsilon4 is associated with greater cognitive decline in middle-aged Caucasian individuals, with a reduced decline among epsilon2 carriers. This suggests that the processes by which APOE genotype mediates dementia risk are operative well in advance of overt dementia.
Blair
C K
CK
Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis 55454, USA.
Folsom
A R
AR
Knopman
D S
DS
Bray
M S
MS
Mosley
T H
TH
Boerwinkle
E
E
D001741:Black or African American; D000368:Aged; D000483:Alleles; D053329:Apolipoprotein E2; D053327:Apolipoprotein E4; D001057:Apolipoproteins E / Q000235:genetics*; D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000235:genetics; D003072:Cognition Disorders / Q000453:epidemiology / Q000235:genetics*; D015331:Cohort Studies; D003920:Diabetes Mellitus / Q000453:epidemiology / Q000235:genetics; D018450:Disease Progression; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D006937:Hypercholesterolemia / Q000453:epidemiology / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011446:Prospective Studies; D014463:Ultrasonography; D044465:White People
D053329:Apolipoprotein E2; D053327:Apolipoprotein E4; D001057:Apolipoproteins E