This is suggested by the studies showing that it is only in women that the plasmatic levels of the enzyme increase after stroke,105 whereas it is only in men that aromatase expression is increased in multiple sclerosis lesions.116 In addition, the association of CYP19A1 gene polymorphisms with AD risk and mild cognitive impairment is more frequent in women than in men,114,128 further suggesting that aromatase activity may have a different effect on the neurodegenerative alterations of males and females. This evidence concerns the gene CYP19A1 and Alzheimer disease.