MTHFR and Alzheimer disease: Genetic effects may be a reason (Bi et al., 2019; Chang et al., 2019; Huang et al., 2019; Li et al., 2019b; Tao et al., 2019), and studies focusing on the effect of Bcl-2 rs956572 (Chang et al., 2018) and MTHFR C677T (Chang et al., 2017) based on SCN showed that homozygotes and heterozygotes exhibited different SCN patterns, although the subjects were all diagnosed with AD.