The presence of ApoE4 in humans is the strongest known genetic risk factor associated with the development of late-onset Alzheimer’s disease as well as poorer outcomes after traumatic brain injury, with links to dementia and cognitive function deficits (Jordan et al., 1997; Teasdale et al., 1997; Merritt and Arnett, 2016). Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.