In that study, we found an interesting trend toward higher concentrations of plasma BDNF in AD patients compared with the MCI group [56], which prompted us to study in more detail the alterations of plasma BDNF levels in individuals with AD compared to subjects with MCI and to further investigate the association of BDNF concentrations with the level of cognitive impairment in these subjects. The gene discussed is BDNF; the disease is Alzheimer disease.