In recent years, many studies have found that brain atrophy in AD and mild cognitive impairment (MCI) patients carrying ApoE ε4 is more prevalent than in non-carriers (Basso et al., 2006; Filippini et al., 2009b; Schuff et al., 2009; Spampinato et al., 2011), and their cognitive decline is also more significant (Okonkwo et al., 2010; Whitehair et al., 2010; Wattmo et al., 2011; Vos et al., 2013; De Beaumont et al., 2016). The gene discussed is APOE; the disease is Brain atrophy.