To investigate whether the APOE*4 allele modified the
relationship between cerebrovascular events and
Alzheimer's disease (AD), we collected evidence of
previous stroke or transient ischemic attack (TIA) and
determined APOE genotype among 102 subjects with AD
and 375 nondemented subjects in a community-based
study of dementia. Subjects with a history of stroke
or TIA were twice as likely to have AD as subjects
without such a history. However, APOE*4 carriers with
a history of stroke/TIA were 5 times more likely than
APOE*4 carriers without such a history to have AD
(odds ratio = 5.3, 95% confidence interval =
1.4-20.9). History of stroke/TIA had little effect on
the likelihood of having AD in subjects without an
APOE*4 allele.