Abstract
With the recent interest in Alzheimer's disease course modification and earlier, even preclinical, intervention, questions have arisen regarding the potentially confounding impact of apolipoprotein E (APOE) genotype on study design, therapeutic outcomes, and even clinical practice. APOE e4 carriers have a faster rate of cognitive decline both preclinically and during the mild cognitive impairment (MCI) stage, and a higher burden of cerebrovascular amyloid that may be the basis for the observed gene-dose-related increased frequency of immunomodulatory therapy-induced meningoencephalitis and cerebral microhemorrhages. To date, this has impacted study design in some research trials but not clinical practice.