Interactions among genetic risk factors like APOE4 and environmental and modifiable lifestyle risk factors in AD have thus far not been well studied, although there are some epidemiological studies consistent with this possibility (Dufouil et al., 2000; Hanson et al., 2013; Rajan et al., 2014; Wirth et al., 2014; Ishioka et al., 2016; Zheng and Li, 2016). Here, APOE is linked to Alzheimer disease.