Given that AD is more common in women than in men (based on FHS data, it was estimated that after the age of 65, one in five women and one in ten men are destined to develop AD [220]), the female-specific association between the rs7946 PEMT SNP and AD is particularly intriguing because, depending on another PEMT SNP (rs12325817 present in an intron), PEMT expression can be modulated by estrogen [195,219,221,222,223,224]. This evidence concerns the gene PEMT and Alzheimer disease.